New Synthetic Method of [2.2]Cyclophanes via Diselena[3.3]cyclophanes

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Abstract
Syntheses of cyclic diselenides through diselenolates and the following deselenation reactions by means of three ways were studied. The preparation of the cyclic diselenides in the presence of excess sodium borohydride gave thirty-eight diselenides containing diselena[3.3]cyclophanes and alicyclic diseleno compounds in high yields in addition to two triple-bridged selenacyclophanes. Photodeselenation of the diselenides in tris(dimethylamino)phosphine afforded series of [2.2]cyclophanes in much higher yields than those of the other two methods, i.e. benzyne-Stevens rearrangement/Raney nickel hydrogenolysis and pyrolytic deselenation at ca. 650 °C. The present study demonstrates that the photodeselenation method, combined with the synthesis of their precursor diselenides, is much superior to the conventional dechalcogenation methods.