Organomolybdän‐ und Organowolfram‐;Reagenzien, IV. über die Chemoselektivität des carbonylmethylenierenden Reagenzes aus 2 MoOCl3(THF)2 und 4 CH3Li

Abstract

Organomolybdenum and Organotungsten Reagents, IV. — About the Chemoselectivity of the Carbonylmethylenating Reagent from 2 MoOCl3(THF)2 and 4 CH3LiFrom a series of carbonylolefinating Mo complexes the reagent “3”, obtained by low‐temperature methylation of two equivalents of MoOCl3(THF)2 with four equivalents of methyllithium and warming up, is especially favourable for chemoselective carbonylolefination reactions. It is readily accessible, reacts at low temperatures, exhibits high aldehydeversus‐ketone selectivity (Tables 1, 2; Scheme 2), high cheleselectivity (preference of a keto group in the α‐ or β‐ position to a hydroxy group before an isolated keto group: Table 4; Scheme 3), and in some cases anticheleselectivity (Table 6). It is nonbasic and tolerates hydroxy groups (even water in the solvent) as well as acyl chloride groups (Table 8). — The chemoselectivity of 3 is compared in several cases with other carbonylolefinating reagents.