Allylzinc reagents carbozincation

Primary allylmagnesium halides and allylzinc reagents react similarly, presumably by an ene-type reaction, to give selectively the cyclopropyl derivative in which the more substituted allylic carbon is attached to the ring (equation 24). Allylzinc compounds have been employed in the same manner in carbozincation of cyclopropenone acetals ... 

One of the first reports dealing with the carbozincation of alkenes by allylic organozinc reagents was the addition of allylzinc bromide to the homoallylic amine 118 which occurred in refluxing THF. A secondary organozinc 119 was regioselectively produced and provided the amine 120 after hydrolysis. A small amount of aminoalcohol 121, resulting from oxidation of 119, was also isolated when the reaction mixture was exposed to air (equation 52)80,81. 

Compared to carboalumination, carbozincation is used less often in organic synthesis4,571. Analogous to carboalumination, stereoselective cis carbozincation of terminal alkynes can be achieved with dialkylzinc reagents or with allylzinc halides in the presence of zirconocene diiodide34-56. Palladium-catalyzed intramolecular carbozincation has been used in the stereoselective synthesis of cyclopentanes72. 

A nickel-catalyzed carbozincation in which an allylzinc adds across the double bond of an unsaturated acetal has also been reported (Scheme 79). ] This procedme effectively provides a reverse-polarity approach to the functionalization of unsaturated carbonyl derivatives. Non-allylic Grignard reagents, however, add to cychc unsaturated acetals with the opposite regiochemistry. This latter procedure provides the basis for an enantioselective conjugate addition to cyclic enones (in 53% ee for the cyclopentenyl substrate and 85% ee for the cyclohexenyl homologue). ... 

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