Directed carbozincation reactions of cyclopropene derivatives.

A diastereoselective procedure has been developed for the Cu-catalyzed addition of diorganozinc reagents to cyclopropene derivatives. Ester and oxazolidinone functions direct the addition of a variety of organozinc reagents with excellent facial selectivity. The resulting cyclopropylzinc reagents can be captured via stereospecific reactions with electrophiles. Cycloprop-2-ene carboxylic esters, which are directly available from the transition-metal-catalyzed reactions of alkynes with alpha-diazo esters, can be utilized directly in carbozincation protocols. Both diastereoselectivity and regioselectivity are high for the carbozincation reactions of 2-alkylcycloprop-2-ene carboxylate esters. The scope of the method is broadened by the ability to utilize organozinc reagents that have been generated in situ from Grignard reagents. Chiral oxazolidinone auxilaries are effective in controlling the diastereoselectivity of the carbometalation reactions.