Regiochemistry of the reaction of deoxygenation of 1-tosylisatin with hexaethyltriamidophosphite

Deoxygenation and desulfonation of organic compounds by the action of trivalent phosphorus derivatives are widely used in organic chemistry [1, 2]. Among the various transformations occurring in this case a group of processes can be separated that are realized in the reactions of carbonyl compounds with P(III) derivatives. For example, the reaction of trialkylphosphites or sodium diethylphosphite with various benzaldehyde derivatives gives rise to the corresponding ethylenes including stilbenes [3, 4] in moderate yields. 2,2'-Diformylbiphenyl and its derivatives undergo the intramolecular cyclization to the corresponding 1,2-diphenyloxiranes under the action of tris(dimethylamino)phosphine [5]. It is assumed that the deoxygenation of 1,3-dicarbonyl compounds (the cyclic anhydrides or thioanhydrides) proceeds through the stage of the carbene formation [6, 7]. In the reactions of aroyland hetaroylphosphonates with trialkylphosphites the formed intermediate of carbene nature is added intramolecularly to the multiple bond [8–14]. Nevertheless, in a considerable number of the studies the intermediate formation of carbenes is only postulated, and other versions of explanation of these synthetic results may be offered. Unlike the deoxygenation of ketones and carboxylic acid anhydrides, similar processes with α-dicarbonyl compounds are described in only few works [4, 15, 16].