The first aza Diels–Alder reaction involving an α,β-unsaturated hydrazone as the dienophile: stereoselective synthesis of C-4 functionalized 1,2,3,4-tetrahydroquinolines containing a quaternary stereocenter

The reaction between aromatic imines and methacrolein dimethylhydrazone in the presence of 10% indium trichloride affords in good to excellent yields biologically and synthetically relevant 1,2,3,4-tetrahydroquinolines bearing a hydrazone function at C-4 in a one-pot process that involves the formation of two C-C bonds and the stereoselective generation of two stereocenters, one of them quaternary, and this constitutes the first example of an alpha,beta-unsaturated dimethylhydrazone behaving as a dienophile in a hetero Diels-Alder reaction and the first vinylogous aza-Povarov reaction.