Strategy to Construct Stair-Shaped Partially Reduced Naphtho[1,2-b]pyrano[2,3-d]oxepines and Dinaphtho[1,2-b,d]oxepines

摘要

A concise and efficient base-induced synthesis of stair-shaped, 4-methylthio-2-oxo-5,6-dihydro-2Hnaphtho[1,2-b]pyran[2,3-d]oxepine-3-carbonitriles (3) has been delineated by the reaction of 3,4-dihydronaphtho[1,2-b]oxepin-5(2H)-one (1) and methyl 2-cyano-3,3-dimethylthioacrylate in DMSO using powdered KOH as a base at room temperature. Amination of 3 has been achieved by reaction with secondary amine in ethanol at reflux temperature to yield 4-sec-amino-2-oxo-5,6-dihydro-2H-naphtho[1,2-b]pyran[2,3-d]oxepine-3-carbonitriles (4). Reaction of 3 with aryl methyl ketone (5) in DMSO at room temperature using powdered KOH as a base produced stair-shaped 5-aryl-7,8-dihydro-1,4-dioxa-2,3-dioxodinaphtho[1,2-b,d]oxepine (6) in good yields. However, reaction of 6-aryl-2H-pyran-2-one-3-carbonitrile (8) with 3,4-dihydronaphtho[1,2-b] oxepin-5(2H)-one (1) did not give similar product, but in lieu 4-aryl-5,6-dihydronaphtho[1,2-b]oxepino[4,5-b]pyran-2-ylidene) acetonitrile (9) was isolated and characterized.