New stereoselective intramolecular [2+2] cycloadditions between ketenimines and imines on an ortho-benzylic scaffold: 1,4-asymmetric induction

Efficient 1,4-asymmetric induction has been achieved in the highly stereoco ntrolled intramolecular [2 + 2] cycloadditions between ketenimines and imin es, leading to 1,2-dihydroazeto[2,1-b]-quinazolines. The chiral methine car bon adjacent to the iminic nitrogen controls the exclusive formation of the cycloadducts with relative trans configuration at C2 and C8. The stepwise mechanistic model, based on theoretical calculations, fully supports the st ereochemical outcome of these cycloadditions.