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

From 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 chemoselecive carbonylolefination reactions. It is readily accessible, reacts dt low temperatures, exhibits high aldehyde-versus-ketone selectivity (Tables 1, 2; Scheme 2), high cheleselectivity (preference of a keto group in the alpha- or beta-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.