Catalytic Desymmetric Cycloaddition of Diaziridines with Metalloenolcarbenes: The Role of Donor-Acceptor Cyclopropenes.

A chiral copper(I) complex catalyzes reactions of symmetric diaziridines with enol diazo compounds, which react through N-N bond ring opening in a formal [3+3] cycloaddition to form four chiral centers with high stereocontrol. A broad spectrum of bridged dinitrogen heterocycles were obtained in high yields and excellent diastereo- and enantioselectivities from γ-substituted enol diazoacetates, while their geometrical isomers gave different enantioselectivities. Donor-acceptor cyclopropenes formed from the geometrical isomers of the γ-substituted enol diazoacetates underwent catalytic ring opening to give only the Z isomer of the metalloenolcarbene intermediate, provided excellent yields and selectivities for the 1,5-diazabicyclo[n.3.1]non-2-ene derivatives.