Direct Synthesis for Benzofuro[3,2-d]pyrimidin-2-Amines via One-Pot Cascade [4 + 2] Annulation/Aromatization between Benzofuran-Derived Azadienes and Carbodiimide Anions.

ABSTRACT

The chemoselective [4+2] annulation/aromatization reactions between benzofuran-derived azadienes and N-Ts cyanamides are developed, affording a convenient method for synthesizing benzofuro[3,2-d]pyrimidin-2-amines under mild conditions. Herein, N-Ts cyanamides selectively participated in reactions absolutely via carbodiimide anion intermediates and the corresponding cyanamide anion intermediates derived products were not observed. The proposed chemoselective stepwise reaction mechanism was well supported by DFT calculations.