Synthesis of 1-aryl-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indoles (1,2,3,4-tetrahydro-β-carbolines) under high pressures

The reactions of aromatic aldehydes with tryptamine (1) in solvents of different polarity were studied. The yields of carbolines in the chosen media decrease with an increase in the donating properties of the aryl substituent, but they markedly increase at a high pressure (5 kbar), especially for compounds with electron-donating aryl groups. The phase transition of dioxane at 5 kbar also sharply increases the yields of the target products.