Photocycloaddition chemistry of 2-(trimethylsilyl)cyclopentenone and 5-(trimethylsilyl)uracil. The utility of a trimethylsilyl group as a removable directing group in photochemistry
The preparation of synthetically useful carbonyl-protected δ- and ε-lithio ketones via reductive lithiation
作者:Shirong Zhu、Theodore Cohen
DOI:10.1016/s0040-4020(97)10230-7
日期:1997.12
and ε-lithioketone equivalents. Primary and tertiary organolithiums have been generated and the ketone function may be part of a ring. The major synthetic use demonstrated in this report is the conversion to mixed heterocuprates which react with acyl chlorides to yield mono-protected 1,6- or 1,7-diketones. The cuprates also undergo conjugateaddition to enones.
An efficient, direct nucleophilic allylicsubstitution of α-, β- and γ-substituted alcohols with enamines, using the Pd(OAc)2/PPh3 catalyst system and ZnBr2 as a promoter in CH2Cl2 at reflux, is reported. The reaction course was dependent on the steric hindrance at the α- or γ-positions with respect to the functionalized α-carbon, selectively affording in moderate to good yields, α- or γ-homoallyl
Versatile desilylative cross-coupling of silyl enol ethers and allylic silanes via oxovanadium-induced chemoselective one-electron oxidation
作者:Toshikazu Hirao、Takashi Fujii、Yoshiki Ohshiro
DOI:10.1016/s0040-4020(01)81753-1
日期:1994.8
The chemoselective cross-coupling of silylenolethers and allylic silanes to γ,δ-unsaturated ketones is achieved by the oxovanadium (V)-induced oxidative desilylation of the more readily oxidizable organosilicon compounds.
Free radical allylations of α-seleno carbonyl compounds with tributyl-substituted 2,4-pentadienyltin, 2-methyl-2-propenyltin, 2-butenyltin, and 3-methyl-2-butenyltin, are described. Such successful C–C bond formations, in particular with the 2-butenyltin and the 3-methyl-2-butenyltin, are owing to the high reactivity of the α-carbon radical, generated from α-seleno carbonyl compounds, toward allylic tin compounds.