REACTIONS OF MYRTENYLZINC BROMIDE WITH CARBONYL-COMPOUNDS - REGIO-SELECTIVITY AND DIASTEREO-SELECTIVITY

The organozinc reagent obtained from (-)-myrtenyl bromide and zinc pow der in THF, under ultrasonic conditions, reacts rapidly with ketones a nd aldehydes furnishing homoallylic alcohols in high yields. The react ions were carried out both with preformed allylzinc compound and under Barbier conditions. Significant regio-and diastero-selectivity was ob served; aldehydes gave preferentially products from a diastereoselecti ve reaction at the most substituted carbon (gamma-allylation) of the a llylzinc reagent, while ketones reacted at the least substituted carbo n (alpha-allylation) and generally with less stereoselectivity. The ab solute configuration of one of the alcohols was determined based on X- ray diffraction.