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| - Palladium-Catalyzed Asymmetric Diene Cyclization/Hydrosilylation Employing Functionalized Silanes andDisiloxanes
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| - Pentasubstituted disiloxanes and silanes of the form HSiMe2CHxPh3-x (x = 1 or 2) reacted withdimethyl diallylmalonate (1) and other functionalized 1,6-dienes in the presence of a catalytic 1:1mixture of (N−N)Pd(Me)Cl [N−N = (R)-(+)-4-isopropyl-2-(2-pyridinyl)-2-oxazoline] [(R)-2] andNaBAr4 [Ar = 3,5-C6H3(CF3)2] to form the corresponding silylated cyclopentanes in good yield withhigh diastereoselectivity. The enantioselectivity of cyclization/hydrosilylation of 1 with disiloxanesand functionalized silanes at −20 °C increased in the following order: HSiMe2OSiMe3 (75% ee) <HSiMe2OSiMe2-t-Bu (80% ee) < HSi(i-Pr)2OSiMe3 (86% ee) = HSiMe2Bn (86% ee) < HSiMe2OSi(i-Pr)3 (89% ee) < HSiMe2OSiPh2-t-Bu (91% ee) < HSiMe2CHPh2 (93% ee). Silylated cyclopentanesderived from HSiMe2OSiMe3 were oxidized with excess KF and peracetic acid at room temperaturefor 48 h to form the corresponding hydroxymethylcyclopentanes in good yield (82−95%). Silylatedcyclopentanes derived from HSiMe2OSiPh2t-Bu were oxidized with a mixture of tetrabutylammonium fluoride and either H2O2 or peracetic acid to form the corresponding alcohols in 48−76%yield. Silylated carbocycles generated from benzhydryldimethylsilane were oxidized with a mixtureof TBAF/KHCO3/H2O2 in 71−98% yield. Asymmetric cyclization/hydrosilylation/oxidation employingbenzhydryldimethylsilane tolerated allylic and terminal olefinic substitution and a range offunctional groups.
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