Microwave‐Assisted Synthesis of Tetrahydro‐β‐carbolines and β‐Carbolines

Abstract

Abstract A microwave‐mediated Pictet–Spengler procedure utilizing 1,2‐dichloroethane (DCE) and trifluoroacetic acid (TFA) was developed to provide tetrahydro‐β‐carboline salts in high yields. Reactions are complete in 20 minutes or less and the product precipitates from solution in high yields and purity, negating the need for liquid–liquid extraction or column chromatography. This method tolerates a wide range of functionality and can be performed on milligram to gram scales. A subsequent microwave‐mediated aromatization of the synthesized tetrahydro‐β‐carbolines to β‐carbolines was also developed utilizing catalytic Pd/C. The aromatization is complete in 60 min or less with most substrates requiring minimal purification.