Isoquinoline ring 3,4-dihydro— from

R = H, OMe) have been prepared from l-aminomethyl-2-naphthols and 3,4-dihydro-isoquinolines. The predominant diastereomer is trans- (at the 7a- and 15-positions), (g) but a surprising inversion at nitrogen can be observed by NMR (nuclear magnetic resonance). Computations support ring-opening at the C(7a)-oxygen bond, giving an iminium-phenolate intermediate. 

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