The reaction of 1-aryl- and 1-pyridyl-1,2,3,4-tetrahydroisoquinolin-3-ones with dimethylcarbamoyl chloride: the preparation of amidines, isoquinolines and N-carbamoylated products

Abstract

1-(Halogenophenyl)-1,2,3,4-tetrahydroisoquinolin-3-ones, such as 3, react with neat dimethylcarbamoyl chloride at 95–165 °C to give high yields of the corresponding N,N-dimethylamidines; higher temperatures favoured N-carbamoylation. At 155 °C the related 1-(3-pyridyl)-1,2,3,4-tetrahydroisoquinolin-3-ones 6–8, 10 and 11 gave lower yields of amidine, with those lactams not bearing an electron-releasing substituent on the benzo ring (6–8) giving medium to good yields of 1-(3-pyridyl)isoquinolines. In contrast, treatment of the corresponding 1-(4-pyridyl)-1,2,3,4-tetrahydroisoquinolin- 3-one 12 with neat dimethylcarbamoyl chloride at temperatures between 125 °C and reflux gave none of the corresponding amidine. At high temperature the N-carbamoylated product 30 predominated, whereas at 125 °C, 3-(N,N-dimethylcarbamoyloxy)-1-(4-pyridyl)isoquinoline 37 was the major product.