Showing papers by "Vadim A. Soloshonok published in 2005"

An efficient and operationally convenient general synthesis of tertiary amines by direct alkylation of secondary amines with alkyl halides in the presence of Huenig’s base

Abstract: A general method for the direct formation of tertiary amines via direct N-alkylation of secondary amines by alkyl halides in acetonitrile in the presence of Hunig’s base is reported. In contrast to methods previously reported in the literature, this procedure is highly functional group tolerant and employs operationally convenient conditions in the absence of transition metal catalysts or solid supports and without formation of the undesired quaternary ammonium salt.

Michael addition reactions between chiral equivalents of a nucleophilic glycine and (S)- or (R)-3-[(E)-enoyl]-4-phenyl-1,3-oxazolidin-2-ones as a general method for efficient preparation of β-substituted pyroglutamic acids. Case of topographically controlled stereoselectivity

Abstract: This paper describes a systematic study of addition reactions between the chiral Ni(II) complex of the Schiff base of glycine with (S)-o-[N-(N-benzylprolyl)amino]benzophenone and (S)- or (R)-3-[(E)-enoyl]-4-phenyl-1,3-oxazolidin-2-ones as a general and synthetically efficient approach to beta-substituted pyroglutamic acids and relevant compounds. These reactions were shown to occur at room temperature in the presence of nonchelating organic bases and, most notably, with very high (>98% diastereomeric excess (de)) stereoselectivity at both newly formed stereogenic centers. The stereochemical outcome of the reactions was found to be overwhelmingly controlled by the stereochemical preferences of the Michael acceptors, and the chirality of the glycine complex influenced only the reaction rate. Thus, in the reactions of both the (S)-configured Ni(II) complex and the Michael acceptors, the reaction rates were exceptionally high, allowing preparation of the corresponding products with virtually quantitative (>98%) chemical and stereochemical yields. In contrast, reactions of the (S)-configured Ni(II) complex and (R)-configured Michael acceptors proceeded at noticeably lower rates, but the addition products were obtained in high diastereo- and enantiomeric purity. To rationalize the remarkably high and robust stereoselectivity observed in these reactions, we consider an enzyme-substrate-like mode of interaction involving a topographical match or mismatch of two geometric figures. Excellent chemical and stereochemical yields, combined with the simplicity and operational convenience of the experimental procedures, render the present method of immediate use for preparing various beta-substituted pyroglutamic acids and related compounds.

Application of Modular Nucleophilic Glycine Equivalents for Truly Practical Asymmetric Synthesis of β‐Substituted Pyroglutamic Acids.

Abstract: A new series of achiral glycine equivalents have been evaluated with respect to their synthetic utility for the production of β-substituted pyroglutamic acid derivatives. Among them, the piperidine-derived complex was found to be a superior glycine derivative for the Michael additions with various (R)-N-(E-enoyl)-4-phenyl-1,3-oxazolidin-2-ones representing a general and practical synthesis of sterically constrained β-substituted pyroglutamic acids. In particular, application of complex allowed for the first time preparation of the corresponding isopropyl derivatives thus increasing the synthetic efficiency and expanding generality these Michael addition reactions.

Synthesis of Fluorine‐Containing Compounds under Operationally Convenient Conditions

Abstract: This paper describes a concept of ‘operationally convenient conditions’, gives a short overview of synthetic applications of bio-mimetic reductive amination under such conditions and discusses new kinetic data on the mechanism of 1,3-proton shift transfer.