Economical synthesis of novel class of heteroatom containing partially reduced polycyclic aromatic hydrocarbons

An efficient and convenient synthesis of 2-oxa- and 2-thia-3,4,7,8-tetrahydro-1H-benzo[c]phenanthrenes has been described through base-induced ring transformation of 2-oxo-4-sec.amino-5,6-dihydro-2H-benzo[h]chromene-3-carbonitriles by 4-oxotetrahydropyran and 4-oxotetrahydrothiopyran, respectively, in excellent yields.