CuBr2-Catalyzed Mild Oxidation of 3,4-Dihydro-ß-Carbolines and Application in Total Synthesis of 6-Hydroxymetatacarboline D.

A green chemical method for the conversion of 3,4-dihydro-ß-carbolines to ß-carbolines has been developed using air as the oxidant. With 15 mol % CuBr2 as the catalyst, 3,4-dihydro-ß-carbolines could be efficiently oxidized to ß-carbolines in dimethyl sulfoxide at room temperature in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (or Et3N). By applying this method, the first total synthesis of 6-hydroxymetatacarboline D was performed through 12 steps in 22% overall yield starting from l-5-hydroxy-tryptophan.

Copper-Catalyzed Benign and Efficient Oxidation of Tetrahydroisoquinolines and Dihydroisoquinolines Using Air as a Clean Oxidant.

A green chemical method for mild oxidation of 1,2,3,4-tetrahydroisoquinolines (THIQs) and 3,4-dihydroisoquinolines (DHIQs) has been developed using air (O2) as a clean oxidant. DHIQs and THIQs could be efficiently oxidized to isoquinolines in dimethyl sulfoxide at 25 °C under an open air atmosphere with CuBr2 (20 mol %) as the catalyst; different bases [NaOEt and/or 1,8-diazabicyclo[5,4,0]undec-7-ene] were used for the reaction according to the patterns of substituents (R1, R2).

Cu-catalyzed mild and efficient oxidation of THßCs using air: application in practical total syntheses of perlolyrine and flazin.

A mild, efficient and environmentally benign method for synthesis of aromatic ß-carbolines via Cu(ii)-catalyzed oxidation of 1,2,3,4-tetrahydro-ß-carbolines (THßCs) was developed, in which air (O2) was used as the clean oxidant. This method has advantages such as environmentally friendliness, mildness, very good tolerance of functional groups, high yielding and easy experiment operation. In addition, this new methodology was successfully applied in the efficient and practical total syntheses of ß-carboline alkaloids perlolyrine and flazin.