ISSN:
0009-2940
Keywords:
Methylenoboranes / (2 + 2)-Cycloadditions / Boraheterocycles / 1,3-Sigmatropic methyl shift
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A 1.3-Methyl Shift along the Unsaturated BCSi SkeletonThe synthesis of the methoxy[tris(trimethylsilyl)methyl]boranes X-(MeO)B-C(SiMe3)3 (1a-d; X = Cl, Br, Ph, PhCH2) is described. The methylenoboranes Me-B=C(SiMe2Hal) (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 MeOSiMe3 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 Ph2CO. The thermal elimination of MeOSiMe3 from Me′-(MeO)B-C(SiMe3)3 (1g;; Me′ = CD3) and subsequent addition of Ph2CO gives the oxboretanes 5g′/5g″ in the ratio of 1:6, showing that an equilibrium Me′-B=C(SiMe32 ⇄ Me - B=C(SiMe3(SiMe2Me′) with a statistical distribution of Me′ among seven methyl places is established in the hot tube before Ph2CO finally attacks the double bond. All these results are in accord with the primary formation of the methyleneboranes X-B=C(SiMe3)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.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19901230416
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