PREPARATION OF ALPHA-ALLENIC AND BETA-ACETYLENIC ALCOHOLS BY TREATMENT OF A MIXTURE OF BU3SNCH=C=CH2 AND RCHO WITH BU2SNCL2 AND WATER

Treatment of a mixture of Bu3SnCHCCH2 and RCHO (R = CH3, C2H5, (CH3)2CH, (CH3)3C) with Bu2SnCl2 in the presence of water gives isomeric mixtures of α-allenic and β-acetylenic alcohols with the α-allenic isomer predominating ( ∼ 75%). Reactions carried out without water give mixtures in which the isomeric ratio between the allenic and acetylenic alcohol varies between 7030 and 5050. In contrast β-acetylenic alcohols predominate when HCHO and α,β-unsaturated aldehydes (R = CH2=CH, CH2=C(CH3), CH3CH=CH, C3H7CH=CH) are used. The stereochemical course of the reactions appear to depend upon the addition and isomerization rates of the Bu2Sn(CH2C=CH)Cl intermediate.