Wittig rearrangements of (heteroaryl)alkyl propargyl ethers - Synthesis of allenic and propargylic alcohols

(Heteroaryl)alkyl propargyl ethers have been synthesized and treated with nBuLi in THF at -78 degreesC. The resulting alpha or alpha'-lithio derivatives could be trapped with iodomethane, affording the corresponding alpha- or alpha'-methylated products. Treatment in the absence of an external electrophile resulted either in allenic alcohols or in propargylic alcohols, or in mixlures of both compounds, probably arising from competing [1,2]- and [2,3]-Wittig rearrangements, in varying ratios. A high anti diastereoselectivity was observed in the propargylic alcohols produced. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.