THE PREPARATION OF SOME 1,7B-DISUBSTITUTED CYCLOPROPA[C]ISOQUINOLINESVIA NITRILE YLIDE CYCLIZATIONS AND THEIR REARRANGEMENT TO 2-BENZAZEPINES AND 4-ALKENYL-1,4-DIHYDROISOQUINOLINES

Diene-conjugated nitrile ylides of the type 1a, having substituents ot her than hydrogen in the R-1 position, cyclise normally to give the C- 7b substituted cyclopropa[c]isoquinolines 2a, In cases where R-2 or R- 3 = H the latter undergo the usual thermal rearrangement to give 5-sub stituted 2-benzazepines 5a, However, when R-2 and R-3 not equal H and either is a CH3 group, then the presence of the C-7b substituent in 2a diverts the thermal rearrangement into a new reaction path leading to the formation of 1,4-dihydro-4-alkenylisoquinolines 14 in high yield.