A facile synthesis of enantiopure 2-aziridinesulfinimines and their highly diastereoselective reactions with phosphite anions

Selectivity in the addition reactions of organometallic reagents to aziridine-2-carboxaldehydes: the effects of protecting groups and substitution patterns

Good to excellent stereoselectivity has been found in the addition reactions of Grignard and organozinc reagents to N-protected aziridine-2-carboxaldehydes. Specifically, high syn selectivity was obtained with benzyl-protected cis, tert-butyloxycarbonyl-protected trans, and tosyl-protected 2,3-disubstituted aziridine-2-carboxaldehydes. Furthermore, rate and selectivity effects of ring substituents, temperature, solvent, and Lewis acid and base modifiers were studied. The diastereomeric preference of addition is dominated by the substrate aziridines' substitution pattern and especially the electronic character and conformational preferences of the nitrogen protecting groups. To help rationalize the observed stereochemical outcomes, conformational and electronic structural analyses of a series of model systems representing the various substitution patterns have been explored by density functional calculations at the B3LYP/6-31G* level of theory with the SM8 solvation model to account for solvent effects.

Synthesis of glycal-based chiral benzimidazoles by VO(acac)2-CeCl3 combo catalyst and their self-aggregated nanostructured materials

VO(acac)(2)-CeCl(3) combo catalyst has been developed for chemoselective cyclocondensation cum oxidation under mild reaction conditions toward synthesis of a new class of optically pure compounds, 2-(2'-C-3',4',6'-tri-O-benzyl/methyl-glycal)-1H-benzimidazoles. It involves an operationally simple synthetic protocol efficient for the syntheses of a wide range of chiral benzimidazoles in high yields without formation of undesired 1,2-disubstituted and pseudoglycal byproducts. Vanadium(V) is found as active oxidant for the chemical processes which is investigated by UV absorption spectroscopy. Highly ordered one-dimensional low molecular mass organic nanostructured materials are fabricated by nanocrystallization of the chiral nanoscale building blocks. Theoretical calculation by the B3LYP/6-31G** level of theory of the glycal-based chiral benzimidazoles shows out of planar geometry of the 1H-anthra[1,2-d]imidazole-6,11-dione moiety, which is responsible for the strong self-aggregation to generate ultralong nanostructured materials. We have also found nice agreement between the theoretical results with the experimental observation in 2D-NOESY experiments. The photophysical property of the solid nanostructured materials is also reported.

An Overview of Stereoselective Synthesis of α-Aminophosphonic Acids and Derivatives

An overview of all methodologies published during the last few years focused to the stereoselective (diastereoselective or enantioselective) synthesis of α-aminophosphonic acids and derivatives is reported. The procedures have been classified according a retrosynthetic strategy and taking into account the formation of each one of the bonds connected to the chiral centre.

Nitrile Biotransformations for the Efficient Synthesis of Highly Enantiopure 1-Arylaziridine-2-carboxylic Acid Derivatives and Their Stereoselective Ring-Opening Reactions

Catalyzed by the Rhodococcus erythropolis AJ270 whole cell catalyst under very mild conditions, biotransformations of racemic 1-arylaziridine-2-carbonitriles proceeded efficiently and enantioselectively to produce highly enantiopure S-1-arylaziridine-2-carboxamides and R-1-arylaziridine-2-carboxylic acids in excellent yields. Although the nitrile hydratase exhibits no selectivity against all nitrile substrates, the amidase is highly R-enantioselective towards 1-arylaziridine-2-carboxamides. When treated with benzyl bromide, 1-phenylaziridine-2S-carboxamide underwent a highly regioselective and enantiospecific ring-opening reaction to afford an almost quantitative yield of R-beta-[(benzyl)phenylamino]-alpha-bromopropanamide (C-2 attack) and R-alpha-[(benzyl)phenylamino]-beta-bromopropanamide (C-3 attack) in a 10.5:1 ratio. Further treatment of the resulting ring-opening products with an N-nucleophilic reagent such as amine and azide led to, through most probably the aziridinium intermediate, the formation of S-alpha-substituted-beta-[(benzyl)phenylamino]propanamides in good chemical yields with high enantiomeric purity.

Synthesis of Enantiopure Sulfinimines (Thiooxime S-Oxides) Catalyzed by Yb(OTf)3 from p-Toluenesulfinamide and Aldehydes in Mild Reaction Conditions

Enantiomerically pure sulfinimines as important building blocks in the asymmetric synthesis of amine derivatives are prepared in good to excellent yields from chiral p-toluenesulfinamide with aromatic, heteroaromatic, and aliphatic aldehydes. The unprecedented feature of the reported procedure is that the formation of the sulfinimines was achieved by the catalytic action of Yb(OTf)(3) in THF at room temperature. The reaction conditions were also applicable to Ellman's sulfinimines.

Formation of P-Ylide under Neutral and Metal-Free Conditions: Transformation of Aziridines and Epoxides to Conjugated Dienes In the Presence of Phosphine

A general approach to formation of the P-ylide from the reaction of aziridines or epoxides with organophosphine under neutral and metal-free conditions is realized. Conjugated diene derivatives based on this kind of P-ylide were prepared in a facile and convenient way.

Facile Preparation of β-Fluoro Amines by the Reaction of Aziridines with Potassium Fluoride Dihydrate in the Presence of Bu4NHSO4

Potassium fluoride combined with tetrabutylammonium bisulfate is an efficient reagent to convert a variety of aziridines derived from cyclic and acyclic alkenes to beta-fluoro amine derivatives in high yield.

Highly diastereoselective strecker reaction of enolizable aliphatic sulfinimines

The reaction of chiral sulfinimines 1c-g derived from aliphatic aldehydes with TMSCN in the presence of CsF gave alpha-amino nitriles in high diastereoselectivity and yield. alpha,beta-Diamino acid derivatives were also obtained in high diastereoselectivity from the reaction of 2-aziridinesulfinimines 1h and 1i followed by ring-opening of the products with thiophenol. The presence of hydrogen at the alpha-position of the C=N double bond is crucial in this TMSCN addition reaction.