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Neue Synthesen von Methyleniminium‐Salzen aus Carbonylverbindungen und aus α‐Chlorethern; ein Zugang zu vinylogen Viehe‐Salzen *

1994; Wiley; Volume: 127; Issue: 10 Linguagem: Inglês

10.1002/cber.19941271026

0009-2940

Werner Schroth, Ullrich Jahn, Dieter Ströhl,

Chemical Synthesis and Analysis

New Syntheses of Methyleniminium Salts from Carbonyl Compounds and from α‐Chloro Ethers; an Access to Vinylogous Viehe Salts * Two methods for the synthesis of isolable methyleniminium salts and amidinium salts are presented. In the first case carbonyl compounds A are treated with a mixture of (dialkyl‐amino)trimethylsilane ( 12 ) and chlorotrimethylsilane ( 13 ) or 12 and trimethylsilyl triflate ( 14 ) leading to the iminium chlorides F or iminium triflates G , respectively. With 12/13 the preparation of F is limited to non‐enolizable aldehydes and dimethylformamide ( 10 ), while 12/14 enables the preparation of G , e.g. 23a–25a, 27a , also with ketones and with substituted amides. The second procedure is based on the treatment of α‐chloro ethers L with 12 . Both methods afford the Mannich reagent 16a in high yields. By reaction of the α‐chloro ether 35 with 12 in diethyl ether the vinylogous Viehe salts 36a–c, e become available for the first time. The reaction pathways are discussed.