Influence of functional substitution of allyl halides on their ni(co)4 promoted carbonylative cycloaddition with acetylenes

The effect of functional substitution of allyl halides on the outcome of the title reaction has been studied. Electron withdrawing and olefinic groups had different effects depending on their location. When they were placed at the central position of the allyl moiety carbonylative cycloaddition was found to be the main reaction, in acetone, to yield exclusively cyclohexenone (or aromatic) derivatives. In contrast, the same groups at the terminal site and in exteded conjugation with the allylic funtion were shown to favour competing side reactions such as allyl self-coupling. However, only cyclopentenones were obtained from either centrally or terminally substituted silylallyl halides. Substitution at both ends of the allyl moiety led to the formation of 4,5-disubstituted cyclopentenones. Important mechanistic information could be achieved from determination of the relative stereochemistry in these compounds.