β-Lactams derived from phenylalanine and homologues: effects of the distance between the aromatic rings and the α-stereogenic reactive center on the memory of chirality
摘要:
The enantioselectivity in the base-promoted cyclization of N-chloroacetyl derivatives of Phe, Phg, and Hph is dependent on the side-chain length, with the best results for Phg analogues (up to 74% ee). In contrast, shortening of the N-substituent, from a (p-methoxy)benzyl group to a (p-methoxy)phenyl moiety, led to a decrease in selectivity. (c) 2006 Elsevier Ltd. All rights reserved.
A transition metal‐free approach for the N‐arylation of amino acid derivatives has been developed. Key to this method is the use of unsymmetricdiaryliodoniumsalts with anisyl ligands, which proved important to obtain high chemoselectivity and yields. The scope includes the transfer of both electron deficient, electron rich and sterically hindered aryl groups with a variety of different functional
work, a mild and transition‐metal‐free approach for the nucleophilic aromatic substitution (SNAr) of unactivated fluoroarenes with primary aliphatic amines to form aromatic amines is reported. This reaction is facilitated by the formation of cationic fluoroarene radical intermediates in the presence of an acridinium‐based organic photocatalyst under blue‐light irradiation. Various electron‐rich and