Copper-Catalyzed Carbomagnesiation of 1-Halocyclopropenes.

We report a versatile copper-catalyzed carbomagnesiation reaction of poly- and fully substituted 1-halocyclopropenyl esters. By fine-tuning the regioselectivity of the addition, we were able to access configurationally stable fully substituted cyclopropyl carbenoid intermediates. These intermediates were subsequently trapped with electrophiles to furnish stereodefined poly- and fully substituted halocyclopropyl esters. The regioselectivity of the addition was found to be dependent on the nature of the sp substituents.