Abstract
An efficient and facile synthetic approach towards a series of novel 3-phenyl-2-oxido/sulfido-2,3-dihydro-1,3,4,2-benzoxadiazaphosphepines 2-7 was described. The method depended on the cyclocondensation of equimolar ratios of salicylaldehyde phenylhydrazone (1) with different examples of phosphorus halides and phosphorus sulfides in toluene containing triethylamine as a catalyst. In the same manner, the fusion of salicylaldehyde phenylhydrazone (1) with triethyl phosphate in the presence of DBU afforded the 2-ethoxy-1,3,4,2-benzoxa-diazaphosphepine 8, while a fusion of compound 1 with diethyl phosphite and tris(2-chloroethyl)phosphite led to the formation of new examples of 1,2-benzoxaphospholes 9 and 10, respectively. Interestingly, the reaction of compound 1 with diethyl ethoxycarbonyl phosphonate in ethanol containing DBU as a catalyst furnished the chromeno[3,4-d][1,2,3]diazaphosphole derivative 12 as a regioselective product.
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