Triphenyl phosphonium perchlorate—an efficient catalyst for the imino Diels–Alder reaction of imines with electron rich dienophiles. Synthesis of pyranoquinoline, furoquinoline and phenanthridine derivatives

Triphenyl phosphonium perchlorate (TPP) is found to be an efficient catalyst for the imino Diels–Alder reaction of aldimines with cyclopentadiene and 3,4-dihydro-2H-pyran is reported for the first time. One pot synthesis of furoquinoline, cyclopentaquinolines and phenanthridine catalysed by TPP is also reported in good yields.