A Facile and Expeditious Synthesis of Cryptosanguinolentines

A simple and efficient synthesis of naturally occurring cryptosanguinolentines is described. Neat reaction of easily accessible 1-methyl-1,2,3,4-tetrahydroquinolin-4-ones and aryl hydrazines in the presence of p-toluenesulfonic acid at 100 degrees C rapidly afforded cryptosanguinolentines in very good yields.