Metal carbene N–H insertion of chiral α,α′-dialkyl α-diazoketones. A novel and concise method for the stereocontrolled synthesis of fully substituted azetidines

The syntheses of all cis substituted azetidines were accomplished in few steps from l-serine in modest to high yields. The key step was based on a rhodium or copper carbenoid N–H insertion of α,α′-dialkyl-α-diazoketones to furnish cis-2,4-dialkyl-azetidin-3-ones as the only observable diastereoisomers.