TRANSITION-METAL-CATALYZED DECOMPOSITION OF SILYLATED DIAZOACETIC ESTERS - INFLUENCE OF SILICON SUBSTITUENTS, CATALYST, AND SOLVENT ON PRODUCT FORMATION

The catalytic decomposition of silylated diazo esters, R1R2R3SiC(N2)COOMe (R1R2R3Si = Me3Si, Et3Si, Me2tBuSi, iPr3Si, Ph2tBuSi, Me3SiSiMe2), by copper(I) triflate, dirhodium tetraacetate, and dirhodium tetrakis(perfluorobutyrate) (Rh2-(pfb)4) in inert solvents has been studied. The efficiency of the catalysts is CuOTf > Rh2(pfb)4 much greater than Rh2(OAc)4- With Rh2(pfb)4, ketenes R2R3(OMe)SiC(R1)=C=O are formed in all cases. With CuOTf, the formal carbene dimers, azines, 5,5-dimethoxy-3,4-bis(SiR1R2R3)-2(5H)-furanones, and the ketenes mentioned before can be obtained; the result depends on the nature of the silyl substituent and on the solvent (carbon tetrachloride or toluene). The X-ray crystal structures of (E)-2a (C12H24O4Si2, orthorhombic space group Pbca, a = 8.987 (1) angstrom, b = 12.076 (1) angstrom, c = 15.329 (7) angstrom, Z = 4) and of 4d (C24H48O4Si2, monoclinic space group P2(1)/c, a = 15.220 (4) angstrom, b = 8.503 (3) angstrom, c = 22.247 (3) angstrom, 103.75 (2)-degrees, Z = 4) have been determined.