- SILICON-DIRECTED BECKMANN FRAGMENTATION
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The selective fragmentation reactions of β-trimethylsilylketoximes have been proved to proceed effectively with acid catalysts giving the corresponding nitriles.Cyclic silylketoximes gave unsaturated nitriles.The fragmentation in the Beckmann rearrangement is completely controlled and directed by a trimethylsilyl group to lead the regio- and stereo-specific formation of the double bond.The catalytic fragmentation proceeds with the combination of trimethylsilyl ketoxime acetates and trimethylsilyl trifluoromethanesulfonate giving nitriles in high yields.Excellent stereospecificity of the fragmentation based on the stereochemical outcome was discussed.Simple stereo-controlled synthetic approach to some insect pheromones is also described.
- Nishiyama, Hisao,Sakuta, Koji,Osaka, Noriyuki,Arai, Hiroyuki,Matsumoto, Makoto,Itoh, Kenji
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p. 2413 - 2426
(2007/10/02)
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- MULTIPLY METALLATED ORGANIC INTERMEDIATES: A TRIS(LITHIOMETHYL)CYCLOHEXANE AND A HEXALITHIOTRIMETHYLCYCLOHEXANETRIOLATE
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Lithium di-t-butylbiphenyl (LiDBB) readily cleaves alkyl-sulphur bonds to yield long-lived organolithiums.Using this reagent trilithio species (2b) was obtained from tris-phenylthioether (1b).The organometallic intermediates (2b) and (5b) were characterised by their reactions with electrophiles (e.g.D2O, CO2, Me3Si-OTf, Me-OTf) to yield di- and hexasubstituted cyclohexanes (3) and (6).Prolonged treatment of the trilithoxy tris-phenylthioether (1c) with excess LiDBB followed by addition of D2O and aqueous work-up gave a methyl-deuterated trimethylcyclohexanetriol (D2.5-3aα) demonstrating that at least one penta- and hexalithio intermediate are involved.The structure of the latter intermediate could not be established unambiguously, but the unsymmetrical 1,1-dilithiated species (2) is prefered over the symmetrical hexalithio species (22) on the basis of extensive transmetallation observed at the tetra- or pentalithio stage (as seen in the deuterated phenylthiomethylcyclohexanetriol (15) and the absence of compelling evidence for the symmetrical tri(deuteriomethyl)cyclohexanetriol (3aβ), as judged from the CH3, CH2D, and CHD2 ratios in the deuterated product (D2.5-3aα).
- Ruecker, Christoph
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p. 135 - 150
(2007/10/02)
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- A NEW REACTION IN ORGANOSILICON CHEMISTRY: THE OXIDATIVE FRAGMENTATION OF γ-HYDROXY SILANES
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The Ce(4+) fragmentation of γ-hydroxy silanes leads to keto-olefins of predictable structure and stereochemistry.
- Wilson, Stephen R.,Zucker, Paul A.,Kim, Chong-wan,Villa, Carmine A.
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p. 1969 - 1972
(2007/10/02)
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- ANIONIC 1,4 OC SILYL REARRANGEMENTS
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γ-Silyloxy-alkyl phenyl thioethers are transformed into γ-silylalcohols by treatment with lithium di-tert-butylbiphenyl.
- Ruecker, Christoph
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p. 4349 - 4352
(2007/10/02)
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- SILICON-DIRECTED BECKMANN FRAGMENTATION. CATALYTIC CLEAVAGE OF CYCLIC β-TRIMETHYLSILYLKETOXIME ACETATES WITH TRIMETHYLSILYL TRIFLUOROMETHANESULFONATE
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Cyclic (E)-β-trimethylsilylketoxime acetates were effectively cleaved by a catalytic action of trimethylsilyl trifluoromethanesulfonate to give the corresponding unsaturated nitriles.The fragmentation in the Beckmann rearrangement is completely controlled
- Nishiyama, Hisao,Sakuta, Koji,Osaka, Noriyuki,Itoh, Kenji
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p. 4021 - 4024
(2007/10/02)
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