Tetrahedron (v.66, #23)
Editorial board (IFC).
Graphical contents list (3979-3987).
Enantioselective CD analysis of amino acids based on chiral amplification with a stereodynamic probe by Marwan W. Ghosn; Christian Wolf (3989-3994).
The condensation between stereolabile 1,8-bis(3′-formyl-4′-hydroxyphenyl)naphthalene, 1, and two amino acid molecules results in the formation of chiral diimines exhibiting strong CD signals. This reaction has been used to develop a chiroptical sensing method for the determination of the absolute configuration and enantiomeric composition of unprotected amino acids. This sensing approach is based on distinctive chiral amplification due to central-to-axial chirality induction within the diimine scaffold formed and does not require the use of an enantiopure ligand or metal complex.Stereodynamic 1,8-bis(3′-formyl-4′-hydroxyphenyl)naphthalene, 1, reacts with two amino acid molecules to a rigid chiral diimine scaffold showing distinctive Cotton effects. In situ CD analysis of the reaction mixture provides information on the enantiomeric excess and the absolute configuration of the substrate.Display Omitted
Keywords: Amino acids; Sensing; Chiral amplification; Circular dichroism; Dynamic stereochemistry;
Reduction of aromatic and aliphatic keto esters using sodium borohydride/MeOH at room temperature: a thorough investigation by Juryoung Kim; Kathlia A. De Castro; Minkyung Lim; Hakjune Rhee (3995-4001).
Reduction of keto esters is a valuable alternative to produce diols. Sodium borohydride/MeOH system at room temperature and short reaction time efficiently reduced α, β, γ, and δ-keto esters having α-keto esters as the most reactive. The ester functionality was reduced effectively due to the presence of oxo group that somehow facilitates the formation of ring intermediate. As expected, the chemoselective experiments showed that ester functionality was not reduced using this system. This study presents a simple, easy, and benign reduction process of various keto esters to its corresponding diols.Display Omitted
Keywords: Alcohols; Reduction; Esters; Keto esters; Sodium borohydride;
Synthesis of triazole analogues of the nanaomycin antibiotics using ‘click chemistry’ by Kris Rathwell; Jonathan Sperry; Margaret A. Brimble (4002-4009).
A series of triazole analogues of the nanaomycin family of antibiotics have been prepared using a ‘click’ dipolar cycloaddition of a naphthalene azide to various alkynes, followed by oxidation to the desired pyranonaphthoquinones.Display Omitted
Keywords: Pyranonaphthoquinone; ‘Click chemistry’; Triazole; Nanaomycin;
A concise and stereospecific synthesis of some cyclitols containing eight-membered rings: cyclooctane-1,2,3,4-tetraoles by Emine Salamci (4010-4015).
A concise and efficient synthesis of cyclooctane-1,2,3,4-tetraoles, new polyhydroxylated eight-membered carbocycles, is described starting from cis,cis-1,3-cyclooctadiene. Cyclooctene endoperoxide obtained by photooxygenation of cis,cis-1,3-cyclooctadiene was the key compound in the synthesis. Reduction of the endoperoxide with zinc or thiourea followed by acetylation of the hydroxyl group and OsO4/NMO oxidation of the double bond gave (1R(S),2S(R),3R(S),4S(R))-cyclooctane-1,2,3,4-tetraol. Interestingly, epoxidation of cyclooctene-1,4-diol with m-CPBA also afforded trans-epoxy-diol 17. (1R(S),2R(S),3R(S),4S(R))-cyclooctane-1,2,3,4-tetraol was easily obtained by hydrolysis of epoxy-diol 17.Display Omitted
Keywords: Cyclitol; Cyclooctanetetraol; Epoxide; Endoperoxide; Synthesis;
A selenolactone-based fluorescent chemodosimeter to monitor mecury/methylmercury species in vitro and in vivo by Xiaoqiang Chen; Kyung-Hwa Baek; Youngmee Kim; Sung-Jin Kim; Injae Shin; Juyoung Yoon (4016-4021).
A fluorescent probe based on selenolactone displays unique fluorescence enhancement and UV–vis spectral change for mercury/methylmercury species, which were attributed to deselenation reaction. The value of this system was successfully demonstrated by its use in detecting inorganic mercury/methylmercury species in cells and zebrafish.A fluorescent probe based on selenolactone displays fluorescence enhancement and UV–vis spectral change for mercury/methylmercury species and is applied to detect the species in vivo.Display Omitted
Keywords: Fluorescent chemodosimeter; Selenolactone; Rhodamine; Mecury; Methylmercury;
Study on the Heck reaction promoted by carbene adduct of cyclopalladated ferrocenylimine and the related reaction mechanism by Gerui Ren; Xiuling Cui; Erbing Yang; Fan Yang; Yangjie Wu (4022-4028).
Carbene adduct of cyclopalladated ferrocenylimine has been successfully applied to Heck reaction of various aryl bromides with olefins. On the basis of kinetic studies, in situ 13C NMR spectra investigations and Hg poisoning experiments, it was proposed that the Heck reaction catalyzed by carbene adduct of cyclopalladated ferrocenylimine proceeded through a classical Pd(0)/Pd(II) cycle and such palladacycle was only a reservoir of the catalytically active Pd(0) species.On the basis of kinetic studies, in situ 13C NMR spectra investigations and Hg poisoning experiments, it was proposed that the Heck reaction catalyzed by carbene adduct of cyclopalladated ferrocenylimine proceeded through a classical Pd(0)/Pd(II) cycle and the palladacycle was only a reservoir of the catalytically active Pd(0) species.Display Omitted
Keywords: Cyclopalladated ferrocenylimine; Heck reaction; Mechanism; Pd(0)/Pd(II) cycle;
Iron/copper promoted oxidative homo-coupling reaction of terminal alkynes using air as the oxidant by Xu Meng; Chuanbin Li; Baochun Han; Tiansheng Wang; Baohua Chen (4029-4031).
An inexpensive catalytic system, which used a readily available Fe(acac)3 and trace quantity of Cu(acac)2 as the co-catalyst and air as the oxidant for the homo-coupling of terminal alkynes, has been developed. The catalytic system could also apply to the cross-coupling reaction of two different terminal alkynes.Display Omitted
Effect of phase transfer chemistry, segmented fluid flow, and sonication on the synthesis of cinnamic esters by Mauro Riccaboni; Elena La Porta; Andrea Martorana; Roberta Attanasio (4032-4039).
Wittig reaction under Phase Transfer conditions was performed in a flow reaction system. Different bases, aldehydes, phosphonium salts, and flow reaction parameters were investigated, in absence of a phase transfert catalyst. An improvement of the reaction outcome (yield and reaction time) was achieved through the immersion of the reactor into an ultrasound bath.Display Omitted
Diketene as an alternative substrate for a new Biginelli-like multicomponent reaction: one-pot synthesis of 5-carboxamide substituted 3,4-dihydropyrimidine-2(1H)ones by Ahmad Shaabani; Mozhdeh Seyyedhamzeh; Ali Maleki; Fatemeh Hajishaabanha (4040-4042).
5-Carboxamide substituted 3,4-dihydropyrimidine-2(1H)one derivatives were synthesized in a simple and efficient method from the one-pot four-component reactions of an aliphatic or aromatic amine, diketene, an aromatic aldehyde and urea or thiourea in the presence of p-toluenesulfonic acid as a catalyst under mild reaction conditions at ambient temperature.Display Omitted
Keywords: 3,4-Dihydropyrimidine-2(1H)one; Multicomponent reaction; One-pot; Urea; Diketene;
Solvent-free cascade reaction: direct multicomponent assembling of 2-amino-4H-chromene scaffold from salicylaldehyde, malononitrile or cyanoacetate and nitroalkanes by Michail N. Elinson; Alexey I. Ilovaisky; Valentina M. Merkulova; Pavel A. Belyakov; Alexander O. Chizhov; Gennady I. Nikishin (4043-4048).
The new type of solvent-free cascade reaction was found: the direct heating of the mixture of salicylaldehyde, malononitrile or cyanoacetate and nitroalkanes at 60 °C in the presence of catalytic amounts of KF or NaOAc results in the formation of 2-amino-4-(1-nitroalkyl)-4H-chromene-3-carbonitriles or methyl 2-amino-4-(1-nitroalkyl)-4H-chromene-3-carboxylates in 80–90% yields. Thus, the new simple and efficient solvent-free ‘one-pot’ way to substituted medicinally privileged 2-amino-4H-chromene scaffold was found directly from such simple and reasonable starting compounds as salicylaldehyde, malononitrile or cyanoacetate and nitroalkanes.Display Omitted
Keywords: Solvent-free reactions; Salicylaldehyde; Malononitrile; Cyanoacetate; Nitroalkanes; 2-Amino-4H-chromenes;
Synthesis of a small library of non-symmetric cyclic sulfamide HIV-1 protease inhibitors by Anna Ax; Advait A. Joshi; Kristina M. Orrling; Lotta Vrang; Bertil Samuelsson; Anders Hallberg; Anders Karlén; Mats Larhed (4049-4056).
A set of 11 non-symmetric cyclic sulfamide HIV-1 protease inhibitors were synthesized and evaluated. The use of a key microwave-assisted silver(I) oxide mediated selective mono N-benzylation reaction enabled fast and straightforward synthesis. The K i values of the new inhibitors ranged between 0.28 μM and >20 μM.Display Omitted
Keywords: HIV-1; Protease inhibitor; Microwave; Palladium catalysis; Benzylation;
Chiral eighteen-component three-dimensional supramolecular entities stabilized by the hydrogen bonding and coordination interactions by Shi-Gui Chen; Yong-Chun Fu; Gui-Tao Wang; Guang-Yu Li; Yuguo Ma; Xi-Kui Jiang; Zhan-Ting Li (4057-4062).
A new class of chiral eighteen-component three-dimensional supramolecular entities has been assembled in toluene and chloroform from twelve zinc porphyrin-appended 2-(ethylamino)- pyrimido[4,5-b][1,8]naphthyridin-4(3H)-one monomers and six chiral bipyridyl compounds. The heterocyclic segments form two C 6-symmetric cyclic hexamers, which are stabilized by a well-established DDA–AAD hydrogen bonding motif, while the six chiral bispyridine ligands are coordinated to the corresponding zinc porphyrin units to give the two-layered architectures. The structures have been characterized by the 1H NMR, UV–vis and circular dichroism experiments, which also reveals that, when the concentration of the monomers is high enough, the chiral supramolecular entity can be formed exclusively.Display Omitted
Keywords: Supramolecular chirality; Hydrogen bonding; Coordination interaction; Porphyrin; Bipyridyl;
Chemical fixation of CO2: efficient synthesis of quinazoline-2,4(1H, 3H)-diones catalyzed by guanidines under solvent-free conditions by Jian Gao; Liang-Nian He; Cheng-Xia Miao; Sébastien Chanfreau (4063-4067).
Guanidines were proved to be efficient catalysts for the chemical fixation of carbon dioxide with 2-aminobenzonitriles under solvent-free conditions. Notably, the catalysts with low loading worked well for a variety of 2-aminobenzonitriles. As a result, quinazoline-2,4(1H, 3H)-diones by employing present protocol were obtained in good yields under mild conditions. This process represents an alternative approach for the greener chemical fixation of CO2 to afford valuable compounds.Display Omitted
Keywords: Quinazolinedione; Aminobenzonitrile; Guanidine; Carbon dioxide; Solvent-free process;
One-pot ethynylation and catalytic desilylation in synthesis of mestranol and levonorgestrel by Fung Fuh Wong; Shih Hsien Chuang; Sheng-chuan Yang; Yu-Hsiang Lin; Wen-Che Tseng; Shao-Kai Lin; Jiann-Jyh Huang (4068-4072).
A one-pot ethylnylation and catalytic desilylation reaction was developed for the synthesis of mestranol and levonorgestrel. Addition of trimethylsilylacetylide to the carbonyl group at C-17 of the steroids yielded the C-17α-trimethylsilylacetylenyl adducts, which were desilylated with a catalytic amount of TBAF (0.050 equiv) in one pot to provide the corresponding mestranol and levonorgestrel both in 90% yields. A plausible mechanism was proposed for the catalytic desilylation through the regeneration of the fluoride ion from the reaction of alkoxide on the steroid with Me3SiF. The one-pot ethynylation and catalytic desilylation methodology provided an alternative route and avoided the traditional use of flammable and explosive acetylene gas toward the synthesis of mestranol and levonorgestrel.Display Omitted
Keywords: Ethynylation; Catalytic desilylation; Propargyl alcohol; Trimethylsilylacetylide; One pot;
Nucleophilic substitution of ferrocenyl alcohols by cerium ammonium nitrate: C–N, C–S, and C–O bonds formation by Ran Jiang; Ying Zhang; Ye-Chen Shen; Xu Zhu; Xiao-Ping Xu; Shun-Jun Ji (4073-4078).
Nucleophilic substitution of ferrocenyl alcohols with N-, S-, O-centered nucleophiles promoted by a catalytic amount of cerium ammonium nitrate (CAN) was studied. By this protocol, a series of second arylamine, thioether, and ether were facilely synthesized in moderate to good yields under mild conditions.Display Omitted
Keywords: Nucleophilic substitution; Ferrocenyl alcohol; CAN; C–X bond formation;
Lectin-bound conformations and non-covalent interactions of glycomimetic analogs of thiochitobiose by Anja Fettke; Markus Kramer; Erich Kleinpeter (4079-4088).
The bound conformations of five S-glycoside analogs of N,N′-diacetylchitobiose as well as their non-covalent interactions with two lectins, Phytolacca americana lectin (PAL) and wheat germ agglutinin (WGA), are reported. The conformations of the ligands were examined by trNOESY experiments and compared with the free, solution-state conformations and molecular modeling data obtained by force field calculations. In the case of S-aryl, S-glycosides with exclusively S-glycosidic linkages, similar free and lectin-bound conformations and non-covalent interactions were found, whereas they differed for mixed glycosides and for a thiazoline derivative. In addition, STD (saturation transfer difference) NMR magnetization transfer efficiencies at three different temperatures were determined and assessed with respect to the structural differences of these pseudosaccharides. The binding epitopes of each substrate with PAL and WGA were also determined.Display Omitted
Keywords: NMR; STD; trNOESY; N,N′-Diacetylchitobiose; PAL; WGA;
Efficient synthesis of the functional central core lactides, a constituent of antibiotic fattiviracins by Eisuke Kaji; Teruaki Komori; Masaki Yokoyama; Tomomi Kato; Takashi Nishino; Tatsuya Shirahata (4089-4100).
An efficient convergent synthetic method has been developed for preparation of various stereoisomers and derivatives of fattiviracins via a common lactide. The synthetic route comprises seco acids prepared by the β-selective glycosylation of chiral 3-hydroxy-4-pentanoate obtained by enzymatic kinetic resolution. The regioselective protection of four individual hydroxy groups was achieved via the 4,6-O-benzylidenation of the glucose moiety from its TMS ethers. The dimeric cyclization of the seco acids under control of reaction concentration afforded the desired lactide without using KH. Our convergent synthetic method was successfully applied to direct installation of side chains to the lactide by cross metathesis to synthesize fattiviracin derivatives. We achieved improvements to the reported method with respect to: (1) synthesis of a convergent synthetic intermediate; (2) stereoselectivity in glycosylation; and (3) establishment of a low cost route suitable for large scale synthesis.Display Omitted
Unusual reactivity of bicyclo[2.2.1]heptene derivatives during the ozonolysis. Part 2 by Céline Reynaud; Michel Giorgi; Henri Doucet; Maurice Santelli (4101-4108).
The ozonation of four bornene derivatives, prepared from (R)-(+)-pulegone, which possess a particularly hindered double bond, led to the formation of unexpected products depending on the nature of the solvent. The formation of the corresponding epoxides, ketones with the same skeleton, various lactones and even an allyl alcohol and an allyl chloride (allylic functionalisation) was observed. In two cases, products presenting a pulegone modified skeleton resulting from a Wagner–Meerwein rearrangement were obtained. The structure of three products was confirmed by crystallographic X-ray analysis. Mechanisms taking into account the rigid and congested structure of the reactants explain these results. The most striking steps were backed up by theoretical calculations.Display Omitted
Keywords: Ozonolysis; Bicyclo[2.2.1]heptene; Pulegone; Wagner–Meerwein rearrangement;
Domino reactions of 5-deoxy-5-iodo-d-xylo- and -l-arabinofuranose derivatives with organometallic reagents. A way towards polyfunctionalized building-blocks by Ariane Bercier; Richard Plantier-Royon; Charles Portella (4109-4114).
Domino reactions involving metal–halogen exchange, furanose ring-opening and nucleophilic addition from 3-O-benzyl-5-deoxy-5-iodo-1,2-O-isopropylidene-α-d-xylofuranose and the epimeric l-arabino derivative with various organometallic reagents are reported. In anhydrous conditions, with a large excess of organolithium or Grignard reagents, vicinal diols are obtained with good yields and a fair diastereoselectivity. Interestingly, with α-trimethylsilyl organolithium reagents, the fragmentation of the furanose ring to the substituted pent-4-enal is followed by a Peterson olefination giving dienic compounds in a four-step one-pot process.Display Omitted
Keywords: Domino reactions; d-xylofuranosides; Metal–halogen exchange; Organometallic reagents; Peterson olefination;
Diastereoselective synthesis of 6-functionalized 4-aryl-1,3-oxazinan-2-ones and their application in the synthesis of 3-aryl-1,3-aminoalcohols and 6-arylpiperidine-2,4-diones by Sven Mangelinckx; Yahya Nural; H. Ali Dondas; Bram Denolf; Reijo Sillanpää; Norbert De Kimpe (4115-4124).
Halocyclocarbamation of benzyl N-(1-phenyl-3-butenyl)carbamates afforded 6-functionalized 4-aryl-1,3-oxazinan-2-ones with moderate to excellent diastereoselectivity depending on the N-substituent. Importantly, in contrast to reported cyclocarbamations of homoallylic carbamates, which are generally trans-diastereoselective, cyclization of N-unsubstituted Cbz-protected homoallylamines led to cis-1,3-oxazinan-2-ones, predominantly. The use of N-benzylated and in situ prepared N-silylated derivatives resulted however in trans-selectivity. Transition states are proposed to explain the stereochemical influence of the N-substituent on the cyclocarbamations. The functionalized 1,3-oxazinan-2-ones could be further elaborated towards biologically or synthetically important 6-arylpiperidine-2,4-diones and 3-aryl-1,3-aminoalcohols.Display Omitted
Keywords: Cyclocarbamation; 1,3-Oxazinan-2-ones; 1,3-Aminoalcohols; Piperidine-2,4-diones;
Synthesis of the western half of breviones C, D, F and G by Francisco A. Macías; Ceferino Carrera; Nuria Chinchilla; Frank R. Fronczek; Juan C.G. Galindo (4125-4132).
The enantioselective synthesis of the diterpenic moiety in the abeo-breviano skeleton is reported. The synthesis is carried out starting from 2-methyl-1,3-cyclohexanedione and EVK in eleven steps following a ring-expansion strategy once the tricyclic perhydrophenantrene skeleton has been obtained. A new Tiffeneau–Demjanov rearrangement under dark conditions is reported in which the insertion of the new methylene group is directed towards the most hindered side of the carbonyl group. This result is new and opposite to those reported in the literature under light (filtered or un-filtered wavelengths) conditions where insertion in the less hindered side is usually preferred.Display Omitted
Keywords: Brevianes; abeo-Brevianes; Tiffeneau–Demjanov; Ring expansion;
Synthesis of 2′-aminoalkyl-1-benzylisoquinoline derivatives and medium sized ring analogues with mu opiod receptor binding activities by Uta Mbere-Nguyen; Alison T. Ung; Stephen G. Pyne (4133-4143).
Novel 2′-aminoalkyl-1-benzylisoquinoline compounds and medium size ring analogues have been prepared using reductive alkylation methods. Four of these analogues were tested for biological activity across 48 different CNS receptors and were showed to have binding activities at the mu opiod receptor.Display Omitted
Stereoselective synthesis of fluorine-containing analogues of anti-bacterial sanfetrinem and LK-157 by Barbara Mohar; Michel Stephan; Uroš Urleb (4144-4149).
The synthesis of (1′S,3R,4R)-4-acetoxy-3-(1′-trimethylsilyloxy-2′,2′,2′-trifluoroethyl)-2-azetidinone (10) precursor of modified carbapenems is described relying upon [Ru(C6Me6)(S,S)–(CH2)5NSO2DPEN]-catalyzed asymmetric transfer hydrogenation under dynamic kinetic resolution using HCO2H–Et3N. This fluorine-containing precursor yielded the targeted trinems 1 and 2 via a stereoselective key step condensation with lithium (S)-6-methoxy-cyclohexenolate.Display Omitted
Keywords: β-Lactam; Asymmetric transfer hydrogenation; Ruthenium; Total synthesis;
Carbenium ion trapping using sulfonamides: an acid-catalysed synthesis of pyrrolidines by intramolecular hydroamination by Charlotte M. Griffiths-Jones (née Haskins); David W. Knight (4150-4166).
Cyclisations of homoallylic sulfonamides proceed smoothly via carbenium ion generation using trifluoromethanesulfonic (triflic) acid, the ease of cyclisation being directly related to the ion stability to give good to excellent yields of the corresponding pyrrolidines. Both toluene- and nitrophenyl-sulfonyl groups are suitable for all substrates tested whereas the corresponding carbamates are only useful in cases of tertiary and highly stabilised carbenium ions. Polyene-derived sulfonamides can also be cyclised to the corresponding polycyclic systems in remarkably high yields, in reactions reminiscent of related cascades encountered in terpene biosynthesis.Cyclisations of homoallylic sulfonamides, both tosyl and nosyl, proceed smoothly via carbenium ion generation using trifluoromethanesulfonic (triflic) acid, the ease of cyclisation being directly related to the ion stability, to give good to excellent yields of the corresponding pyrrolidines. Polyene-derived sulfonamides can also be cyclised to the corresponding polycyclic systems in remarkably efficient cascade reactions.Display Omitted
Keywords: Cyclisation; Hydroamination; Sulfonamides; Triflic acid; Pyrrolidines;
Alkylation and aldol reactions of acyl derivatives of N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine: asymmetric synthesis of α-alkoxy-, α-substituted-β-alkoxy- and α,β-dialkoxyaldehydes by Alexander N. Chernega; Stephen G. Davies; Ai M. Fletcher; Christopher J. Goodwin; David Hepworth; R. Shyam Prasad; Paul M. Roberts; Edward D. Savory; Andrew D. Smith; James E. Thomson (4167-4194).
Treatment of a range of O-protected glycolate derivatives of the chiral auxiliary N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine with KHMDS in the presence of 18-crown-6 followed by addition of an alkyl halide generates α-substituted derivatives with very high levels of diastereoselectivity. Alternatively, reaction of the potassium enolate of a propanoate or O-protected glycolate derivative of N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine with a range of aldehydes gives syn-aldol products with high levels of diastereoselectivity. These adducts may be reductively cleaved with LiAlH4 to give enantiopure α-alkoxy-, α-substituted-β-alkoxy- and α,β-dialkoxyaldehydes in good yield.Alkylation or aldol reactions of enolates of acyl derivatives of the chiral auxiliary N-1-(1′-naphthyl)ethyl-O-tert-butylhydroxylamine proceed with high levels of diastereoselectivity. Subsequent reductive cleavage with LiAlH4 gives access to enantiopure α-alkoxy-, α-substituted-β-alkoxy- and α,β-dialkoxyaldehydes.Display Omitted
Keywords: Weinreb amide; Glycolate enolate; Diastereoselective alkylation; Aldol reaction;
Novel chiral C 1-1′,2′,3′,4′-tetrahydro-1,1′-bisisoquinolines: synthesis, resolution, and applications in catalytic enantioselective reactions by Gao Qi; Yao Qiong Ji; Zaher M.A. Judeh (4195-4205).
A straightforward synthesis of a structurally constrained C 1-1′,2′,3′,4′-tetrahydro-1,1′-bisisoquinoline 1 is described. Resolution of this compound has been achieved successfully. The preparation of chiral N-alkyl, urea, and thiourea derivatives as potential new chiral ligands, based on the parent compound 1, is reported. Chiral compound 1 induced very good selectivity and yield in the addition of either Et2Zn (85% ee, 96% yield) or nitromethane (85% ee, 60% yield) to benzaldehyde.The structurally constrained C 1-1′,2′,3′,4′-tetrahydro-1,1′-bisisoquinoline (+)-1 was synthesized and resolved. Various derivatives were prepared from (+)-1. Application of (+)-1 in asymmetric C–C bond forming reactions gave very good enantioselectivity and yield in either the addition of Et2Zn (85% ee, 96% yield) or CH3NO2 (85% ee, 60% yield) to benzaldehyde.Display Omitted
Keywords: Bisisoquinolines; Bischler–Napieralski reaction; C–C bond forming reactions; Henry reaction;
Shape selectivity in the synthesis of chiral macrocyclic amides by Stefano Colombo; Carmine Coluccini; Marco Caricato; Claudia Gargiulli; Giuseppe Gattuso; Dario Pasini (4206-4211).
Shape-persistent, optically-active arylamide macrocycles have been designed and approached by using a stepwise, convergent methodology. The source of chirality, an axially-chiral Binol scaffold, incorporates methoxy functionalities in the 2,2′ positions, and carboxylic functionalities in the external 3,3′ positions. The latter can be efficiently elaborated through aromatic amidation to introduce aromatic spacers of differing shapes. The peculiar arrangement of functionalities on the Binol skeleton functions as an element of rigidification of the covalent structure through the formation of stable intramolecular hydrogen bonds. When this element is counterbalanced by the use of a flexible 3,3′-diaminobiphenyl as a spacer, yields for the macrocyclization step increase to values higher than 50%. The recognition properties of this particular macrocycle have been exploited and, while they indicate modest binding affinities towards carboxylate anions, the additional stabilization of neighbouring amide functionalities suitably placed within the covalent framework induces detectable binding of proper difunctional carboxylates.Display Omitted
Keywords: Chirality; Amides; Macrocycles; Anion recognition; Supramolecular chemistry;
Rhodium-catalyzed synthesis of γ-butyrolactams and pyrrolidines via cycloisomerization of N-tethered 1,6-enynes by Jianping Wang; Xiaomin Xie; Fangfang Ma; Zhiyong Peng; Lei Zhang; Zhaoguo Zhang (4212-4217).
A rhodium-catalyzed cycloisomerization reaction of N-tethered 1,6-enynes with an intramolecular halogen shift has been developed, providing a useful process for the synthesis of stereo defined γ-butyrolactam and pyrrolidine derivatives in good to excellent yields. Effects of both electronic feature and steric structure of the substrates on the outcome of the reaction were investigated.Display Omitted
CuI/La(OTf)3 catalyzed, one-pot synthesis of isomeric ellipticine derivatives in ionic liquid by Vikram Gaddam; Subburethinam Ramesh; Rajagopal Nagarajan (4218-4222).
An efficient method for one-pot synthesis of isomeric ellipticine derivatives through CuI/La(OTf)3 catalyzed sequential inter/intramolecular cyclization of substituted alkynes with imines followed by aromatization is reported in good to excellent yields.Display Omitted
Keywords: Copper catalysis; Ionic liquid; Isomeric ellipticine; Lanthanum triflate;
Donor–acceptor organic sensitizers assembled with isoxazole or its derivative 3-oxopropanenitrile by Yi-Tsung Li; Chao-Ling Chen; Yu-Yen Hsu; Hui-Chu Hsu; Yun Chi; Bo-So Chen; Wei-Hsin Liu; Cheng-Hsuan Lai; Tsung-Yi Lin; Pi-Tai Chou (4223-4229).
A series of new donor–acceptor organic sensitizers LJ5–LJ7 assembled with isoxazole or its derivative 3-oxopropanenitrile was synthesized and used in dye-sensitized solar cells to study the effect of both π-spacers and anchoring groups on device performance. X-ray crystal structure analyses show planar arrangement of dithiophene and isoxazole fragments, providing an excellent π conjugation and hence the large electronic coupling between the triphenylamine donor and electron acceptor units. For the DSSC applications, the derived photophysical and photovoltaic properties revealed a lower η value of 1.06% (LJ7) and 2.41% (LJ5), and 3.30% (LJ7) for the dyes with rhodanine-3-acetic acid, cyanoacetyl group, and vinyl cyanoacetic acid as the anchor. Electrochemical impedance spectroscopy was used to determine the interfacial charge transfer process occurring in solar cells that employed different dyes.Display Omitted
Keywords: Dye-sensitized solar cell; Dithiophene; Isooxazole; Cyanoacetic acid;
Synthesis, characterization and DFT calculations of new ethynyl-bridged C60 derivatives by Simon Rondeau-Gagné; Carles Curutchet; François Grenier; Gregory D. Scholes; Jean-François Morin (4230-4242).
A new series of soluble C60 derivatives for organic electronic application has been synthesized by ethynylation reaction using different electron-donating and electron-withdrawing groups of varying length.Display Omitted
Keywords: Fullerene; OPE; DFT Calculations; Electrochemistry;
Gas-phase pyrolysis of benzimidazole derivatives: novel route to condensed heterocycles by Maher R. Ibrahim; Talal F. Al-Azemi; Alya Al-Etabi; Osman M.E. El-Dusouqui; Nouria A. Al-Awadi (4243-4250).
Gas-phase pyrolysis of N-(1H-benzimidazol-2-yl)-N′-arylidenehydrazines 1a–e gave the corresponding arylnitriles 2a–e, 2-aminobenzimidazole 3, 2,4,5-triphenylimidazole 4, 1,3-diphenyl-8H-2,3a,8-triazacyclopenta[a]indene 5, and 5,11-diphenyl-6H,12H-dibenzimidazo[1,2-a];1’,2’-d]pyrazine 6. The kinetics and analysis of the products of reaction are reported and used to elucidate the mechanism of the elimination process.Display Omitted
Keywords: Benzimidazol-2-yl-N′-arylidenehydrazine; 2-Aminobenzimidazole; Triazacyclopenta[a]indene; Azaindino[1,2-b]fluorine; Gas-phase pyrolysis; Mechanism;