Carbometallation propargylic alcohol

Scheme 5.23 Carbometallation of (homo)propargylic alcohols reported by Zhang and Ready.

Duboudin s Cu-catalyzed anti carbomagnesiation of propargyl alcohol derivatives is one of still a small number of currently known carbometallation reactions of very high (>98%) regio- and stereoselectivity (Scheme 3.13b), which can be profitably exploited, as ejKmphfied by the efficient and highly selective synthesis of both (F)-and (Z)-y-bisabolenes (Scheme 3.35) [74]. 

Scheme 10.87 Iron-catalyzed carbometallation of propargylic alcohols [72].

Thus, the optimized carbometallation reaction of propargylic alcohols with aromatic Grignard reagents proceeds without an additional metal catalyst and leads to the formation of an alkenyl fluoride. The stereoselective defluorometallation proceeds to form predominantly the fluorinated (Z)-carbon-carbon double bond in the final allene 276. Two reasons were proposed by the authors for such a high level of stereoselectivity the defluorometallation is favored from the intermediate... 

Normant has reviewed the carbometallation of alkynes to give stereospecific syntheses of alkenyl-metal derivatives, and their addition to aldehydes and ketones to afford allylic alcohols. Specific titanium-catalysed 5yn-hydromag-nesiation of 2-propynylic alcohols (Scheme 16), and the related zirconium-catalysed 5yn-carboalumination of propargylic alcohol itself (also Scheme 16) or its t-butyldimethylsilyl ether (c/. 3, 139 4,160) can both lead to allylic alcohols. 

Other Unsaturated Alcohols. The review mentioned above of carbometallation of alkynes, includes a survey of additions of alkenyl-metal derivatives to epoxides to give homoallylic alcohols. The zirconium-catalysed carboalumination of propargylic systems (Scheme 16) is also applicable to the homopropargylic to homoallylic alcohol transformation. ... 

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