convenient synthesis of partially hydrogenated functionalized [5]helicenes and oxa[5]helicenes, such as (1,2,5,6-tetrahydro-3-oxa-dibenzo[c,g]phenanthren-4-ylidene)acetonitriles 6 and (5,6-dihydro-3-oxa-dibenzo[c,g]phenanthren-4-ylidene)acetonitriles 8, has been developed through base-catalyzed ring transformation of 5,6-dihydro-4-amin-1-yl-2-oxo-2Hbenzo[h]chromene-3-carbonitriles 4 by 2-tetralones 5. The