Organic synthesis via Organosilicon-Transition Metal Combined Systems

1994 Fiscal Year Final Research Report Summary

• Project/Area Number: 05453137
• Research Category: Grant-in-Aid for General Scientific Research (B)
• Allocation Type: Single-year Grants
• Research Field: Synthetic chemistry
• Research Institution: KYOTO UNIVERSITY
• Principal Investigator: TAMAO Kohei Kyoto University Institute for Chemical Research Professor, 化学研究所, 教授 (60026218)
• Project Period (FY): 1993 – 1994
• Keywords: transition-metal catalyst / thermal degradation / pentacoordinated disilane / skeletal rearrangement / (alkoxy) oligosilane / silylene

Research Abstract

1. A pentacoordinated ethoxydisilane, which contains the 8-dimethylamino-1-naphthyl group and ethoxy group on the same silicon atom, was prepared. The X-ray structure analysis revealed that the geometry of the particular silicon atom was deformed from tetrahedral to trigonal bipyramidal. The ethoxydisilane underwent thermal degradation readily at 90ﾟC in DMF or at 110ﾟC in toluene to form ethoxysilane in high yields. The resulting silylene species was trapped efficiently with 2,3-dimethylbutadiene and diphenylacetylene to form the corresponding adducts in high yields. A similar degradation occurred under much milder condition at 50ﾟC in the presence of a Ni (0) or Pd (0) complex as catalyst.
2.Poly (alkoxy) trisilanes and tetrasilanes were prepared readily by a new method. These oligosilanes were found to undergo skeletal rearrangement in the presence of Pd (PPh_3)_4 as a catalyst at 80-140ﾟC in the fashion that the internal silylene moiety transferred to the terminal positions. Ten substrates were examined. Typically, 1,2,3- (MeO)_3Me_5Si_3 and 1,2,3,4- (MeO)_4Me_6Si_4 were converted into the 1,1,3-isomer and 1,1,4,4-isomer, respectively, in quantitative yield. A proposed mechanism involved silylene transfer via a bis (silyl) (silylene) Pd complex as a key intermediate.