P-Methylhomoallyl alcohols

P-Methylhomoallylic alcohols.2 These crotylboronates (1) react with aldehydes to give /3-methylhomoallylic alcohols with a diastereoselectivity of > 95% (equations I and II). This condensation has certain advantages over the aldol condensation, since the products 2 can be converted to / -hydroxy aldehydes or carboxylic acids by... 

Crotylization of RCHO.1 (E)- and (Z)-Crotyltrifluorosilanes add to aldehydes in the presence of CsF to give anti- and vyn-p-methylhomoallyl alcohols, respectively, with high diastereoselectivity. 

The reaction of the (Z)-crotyldiisopinocampheylborane derived from (+-)-a-pinene with aldehydes at -78 °C, followed by oxidative workup, furnishes the corresponding j yn-P-methylhomoallyl alcohols with 99% diastereoselectivity and 95% enantioselectiv-ity. Use of (Z)-crotyldiisopinocampheylborane derived from (-)-a-pinene also produces 5yn-alcohols with 99% diastereoselectivity but with opposite enantioselectivity, an example of reagent control. 

Brown HC, Bhat KS. Chiral synthesis via organoboranes. 7. Diastereoselective and enantioselective synthesis of erythro- and threo-p-methylhomoallyl alcohols via enantiomeric (Z)- and (E)-crotylboranes. J. Am. Chem. Soc. 1986 108 5919-5923. 

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