Electrosynthesis of cyclopropanone adducts

Electroreduction of α,α′-dihalo ketones to cyclopropanones (isolated as the hemiacetals or hemiacylals) is accomplished with good yields only with highly alkylated α,α′-dihalo ketones. Attempts to prepare little substituted or unsubstituted cyclopropanone (derivatives) by electroreduction of α,α′-dihalo ketones in which the carbonyl group is protected as an acylal or aminal resulted in the isolation of the desired compounds in low yields. The cyclisation reaction cannot compete successfully with side-reactions. With acetals as the protecting group, the reductive cyclisation proceeds smoothly. Contrary to the acetals, the cyclopropanone acylals are excellent precursors for cyclopropanone.