new intermediates and processes for preparing 6 - halo - 7 , 8 - dihydroxy - 1 -- 2 , 3 , 4 , 5 - tetrahydro - 1h - 3 - benzazepines involve the reaction of a p - methoxyphenylglyoxal , lower alkyl hemimercaptal with a 2 - chloro - 3 , 4 - dimethoxyphenethylamine , followed by a borohydride reduction .