Vishnu K. Tandon, Hardesh K. Maurya, Balendu Kumar, Brijesh Kumar, Vishnu Ji Ram
An efficient concise synthesis of 4-methylthio-2-oxo-5,6-dihydro-2H-benzo[b]pyrano[2,3-d]oxepine-3-carbonitriles has been delineated through condensation-cyclization of 3,4-dihydro-2H-benzo[b]oxepin-5(2H)-ones and methyl 2-cyano-3,3-dimethylthioacrylate in DMF using powdered KOH as a base. A base-induced reaction of 3,4-dihydro-2H-benzo[b]oxepin-5(2H)-ones and 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitrile in the presence of powdered KOH in DMF gave an isomeric mixture of (E)- and (Z)-2-(4-phenyl-5,6-dihydro-2H-benzo[b]pyrano[2,3-d]oxepin-2-ylidene)acetonitriles. However, the ring transformation of 6-aryl-4-(sec-amino)-2H-pyran-2-one-3-carbonitriles from 3,4-dihydro-2H-benzo[b]oxepin-5(2H)-ones under analogous reaction conditions exclusively gave 8-phenyl-10-(sec-amino)-6,7-dihydrodibenzo[b,d]oxepine-11-carbonitriles.
An efficient concise synthesis of 4-methylthio-2-oxo-5,6-dihydro-2H-benzo[b]pyrano[2,3-d]oxepine-3-carbonitriles has been delineated through condensation-cyclization of 3,4-dihydro-2H-benzo[b]oxepin-5(2H)-ones and methyl 2-cyano-3,3-dimethylthioacrylate in DMF using powdered KOH as a base. A base-induced reaction of 3,4-dihydro-2H-benzo[b]oxepin-5(2H)-ones and 6-aryl-4-methylthio-2H-pyran-2-one-3-carbonitrile in the presence of powdered KOH in DMF gave an isomeric mixture of (E)- and (Z)-2-(4-phenyl-5,6-dihydro-2H-benzo[b]pyrano[2,3-d]oxepin-2-ylidene)acetonitriles. However, the ring transformation of 6-aryl-4-(sec-amino)-2H-pyran-2-one-3-carbonitriles from 3,4-dihydro-2H-benzo[b]oxepin-5(2H)-ones under analogous reaction conditions exclusively gave 8-phenyl-10-(sec-amino)-6,7-dihydrodibenzo[b,d]oxepine-11-carbonitriles.
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