Ylides by the desilylation of .alpha.-silyl onium salts

Abstract

Conventional ammonium, phosphonium, and sulfonium ylides are usually generated from the corresponding "oniumn salt by deprotonation with strong base. No other method is necessary if the starting salts have only one available site for a-proton removal and if the resulting ylides are relatively stable. These conditions are met for typical Wittig reagents (RCH2P+Rh3

Application of an intramolecular dipolar cycloaddition to an asymmetric synthesis of the fully oxygenated tricyclic core of the stemofoline alkaloids

“…17-21 Non-stabilized azomethine ylides are often generated by desilylation of iminium salts derived from the O-activation of amides 17,22 or the N-alkylation of vinylogous imidates. 23 In a related strategy, we recently reported the use of N-(trimethylsilyl)methyl vinylogous amides as precursors to azomethine ylides suitable for the preparation of substituted pyrrolizidines and indolizidines.…”

Thermal intramolecular reactions of Δ1-1,2,4-triazolines with extended exocyclic unsaturation

“…Although compound X remains an unknown, it is clearly not 13 and it cannot be derived from 14. Thus, reaction [4] appears to be excluded.…”

“…Careful separation of A'-1,2,4-triazoline have been described. As cross-conjugated the products by means of centrifugal chromatography under N2 azoenarnines with extended conjugation, 1 and 3 held promise (Chromatotron) afforded pyrroles 5 and 6 in 91% combined for the generation of azomethine ylides (3,4). Thus, 1 and yield, eq.…”

Synthesis of spiropyrrolidines: 1,3-dipolar cycloaddition reactions of an azomethine ylide to unusual dipolarophiles; a molecular orbital study of the cycloaddition reaction

“…Among the various synthetic strategies, 1,3-dipolar cycloaddition reactions of azomethine ylides occupy a unique position in the synthesis of pyrrolidines [2]. A number of methods have been developed for the generation of ylides such as the desilylation approach conceived by Vedejs [3] and the tautomerism route by Grigg [4]. The generation of azomethine ylides by thermolysis of aroyl aziridines has attracted considerable attention because of the potential of these compounds to give pyrrolidine derivatives by electrocyclic ring opening and their ability to cycloadd to olefinic compounds.…”