Addition Reactions of Maleic Anhydride to a Disilene and a Tetrasilabuta-1,3-diene: Formation of Bi- and Tetracyclic Compounds^1,2

The reaction of hexakis(2,4,6-triisopropylphenyl)tetrasilabutadiene with maleic anhydride (3) furnishes the 2,9-dioxa-5,6,7,8-tetrasilatetracyclodecan-3-one derivative 4, presumably by a sequence of two consecutive [2 + 2] cycloadditions. Tetrakis(2,4,6-triisopropylphenyl)disilene reacts with 3 to afford the bicyclic 1,2-dihydrofuro[3,2-d][1,2,3]oxadisilol-5(6H)-one derivative 5 via a formal [2 + 3] cycloaddition and a 1,2-hydrogen shift. The structures of 4 and 5 were determined by X-ray crystallography.