Portal de Periódicos da CAPES

Eine 1,3‐Methyl‐Verschiebung an der ungesättigten BCSi‐Kette

1990; Wiley; Volume: 123; Issue: 4 Linguagem: Inglês

10.1002/cber.19901230416

0009-2940

Peter Paetzold, Thomas A. Schmitz, A. Tapper, Ralf Ziembinski,

Organometallic Complex Synthesis and Catalysis

A 1.3‐Methyl Shift along the Unsaturated BCSi Skeleton The synthesis of the methoxy[tris(trimethylsilyl)methyl]boranes X‐(MeO)B–C(SiMe 3 ) 3 ( 1a‐d ; X = Cl, Br, Ph, PhCH2) is described. The methylenoboranes Me‐B=C(SiMe 2 Hal) ( 3a, b ), the 2,3‐dihydro‐1H‐1‐sila‐3‐boraindene species 6 , and the 1,2,3,4‐tetrahydro‐1‐sila‐3‐boranaphthalene species 7 are formed by the thermal elimination of MeOSiMe 3 from 1a/b or 1c or 1d , respectively. The boranes 3a, b undergo cyclodimerization at the B=C bond at 25 and 69°C, respectively, the diboretanes 4a, b being formed. The oxaboretanes 5a, b are isolated from the reaction of 3a, b with Ph 2 CO. The thermal elimination of MeOSiMe 3 from Me′‐(MeO)B–C(SiMe 3 ) 3 ( 1g; ; Me′ = CD 3 ) and subsequent addition of Ph 2 CO gives the oxboretanes 5g′/5g″ in the ratio of 1:6, showing that an equilibrium Me′‐B=C(SiMe 3 2 ⇄ Me—B=C(SiMe 3 (SiMe 2 Me′) with a statistical distribution of Me′ among seven methyl places is established in the hot tube before Ph 2 CO finally attacks the double bond. All these results are in accord with the primary formation of the methyleneboranes X‐B=C(SiMe 3 ) 2 from 1a‐d , followed by a 1,3‐shift of Me along the unsaturated BCSi skeleton and the subsequent transformation into the isolated products.