Asymmetric Synthesis of 3-Substituted Dihydro-2H-isoquinolin-1-ones, Dihydro- and Tetrahydroisoquinolines via 1,2-Addition/Ring Closure

ABSTRACT The asymmetric synthesis of 3-substituted dihydro-2H-isoquinolin-1-ones, dihydro- and tetrahydroisoquinolines is described. The key operation is a tandem 1,2-addition/ring closure sequence employing lithiated ORTHO-toluamides and aldehyde SAMP- or RAMP-hydrazones as substrates, followed by N-N bond cleavage to remove the auxiliary. Moderate to good yields and high enantiomeric excesses (ee = 85-99%) are reached.