Reduction and Carboxylation of 1-Chloromethyl-6,7-Dimethoxy-3,4-Dihydroisoquinolinium Salts. An Easy Entry to 1-Hydroxymethyl-1,2,3,4-Tetrahydroi Soquinoline Alkaloids
At 25 .deg. C , the NaBH/sub 4//MeOH reduction of the title isoquinolinium salts gave the aziridine exclusively. At a low temperature (0 .deg. C ) in the presence of CO/sub 2//K/sub 2/CO/sub 3/, the 2-oxazolidinone was obtained in almost quantitative yield. Controlled hydrolysis of the borane complex derived from the isoquinolinium salts also gave the cyclic carbamate. (.+-.)-Calycotomine and its N-Me derivative were obtained in high yields.