Diversity in Coupling Reactions of Acetylene-Titanium Complexes and Hetero-substituted Allenes

摘要

Acetylene-titanium complexes prepared from acetylenes and a titanium(II)alkoxide were allowed to react with hetero-substituted allenes to undergo i)a simple coupling reaction,ii)a coupling reaction followed by elimination of the hetero-substituent,or iii)a coupling reaction accompanied by isomerization.Coupling reactions of allenes and acetylenes by the use of group 4 metal species have already been reported.1 However,no information on the coupling reaction involving heterogroup-functionalized allenes is available.We report herein that three different pathways,which are formulated in Scheme 1,were observed in the coupling reaction of acetylene-titanium(II)alkoxide complexes 1 with hetero-substituted allenes 2.Paths a,b,and c eventually afforded i)simple coupling products upon hydrolysis,ii)skip enynes via elimination of the hetero-substituents,and iii)conjugated dienes via the intramolecular addition-rearrangement sequence,respectively.