Ultrasound Assisted Pictet–Spengler Synthesis of Tetrahydro‐β‐Carboline Derivatives

The synthesis of twelve tetrahydro‐β‐carboline derivatives 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l prepared via the Pictet–Spengler reaction is described. The reaction of tryptamine and a variety of arylaldehydes were carried out under ultrasonic irradiation and trifluoracetic acid catalysis at room temperature. These tetrahydro‐β‐carbolines have been synthesized in higher yields and shorter reaction times compared to the conventional method. Moreover, the reaction proceeded successfully even employing arylaldehydes with electron‐donating or electron‐attracting substituents which did not react under conventional method.