On the 6-endo Selectivity in 4-Penten-1-oxyl Radical Cyclizations
摘要:
Regioselectivities in cyclizations of 4-substituted 4-penten-1-oxyl radicals have been investigated in a combined experimental and computational study (density functional theory). The progressive increase of the 6-endo-trig selectivity along the series of 4-substituents H < CH3 < C(CH3)(3) < C6H5 has been interpreted to originate from a balance between strain and FMO interactions. Torsional strain, which is associated with geometrical changes upon an approach of the reacting entities, is relevant for the 6-endo-trig but not for the 5-exo-trig reactions, as seen, for instance, in selective tetrahydrofuran formation from the 4-penten-1-oxyl radical and its 4-methyl derivative. The preference for tetrahydropyran formation in cyclizations of the 4-tert-butyl and the 4-phenyl-4-penten-1-oxyl radical has been attributed to FMO interactions between the terminal carbon atom of the pi bond and the O-radical center thus favoring the 6-endo-trig reaction on the basis of lower transition state energies.
Yttrium triflate-catalyzed addition of lithium enolates to 1,2-epoxides. Efficient synthesis of γ-hydroxy ketones
作者:Paolo Crotti、Valeria Di Bussolo、Lucilla Favero、Franco Macchia、Mauro Pineschi
DOI:10.1016/s0040-4039(00)78266-9
日期:1994.8
A simple, efficient method is described for the synthesis of γ-hydroxy ketones by the direct opening of 1,2-epoxides with lithiumenolates derived from simple ketones in anhydrous toluene, in the presence of Y(OTf)3.
Alkylation of carbonyl compounds in the TiCl4-promoted reaction of trimethylsilyl enol ethers with epoxides
作者:Gojko Lalić、Željko Petrovski、Danica Galonić、Radomir Matović、Radomir N Saičić
DOI:10.1016/s0040-4020(00)01028-0
日期:2001.1
Titanium tetrachloride promoted reaction of trimethylsilyl enol ethers with ethylene oxide affords homoaldol type products in moderate/good yields. Monosubstituted epoxides react regioselectively: the nucleophilic attack of the enolate occurs at the more substituted position of propene oxide whereas epichlorohydrin reacts at the less substituted end.
POSITIVE PHOTOSENSITIVE RESIN COMPOSITION AND METHOD FOR FORMING PATTERNS BY USING THE SAME
申请人:LIU Chi-Ming
公开号:US20120328799A1
公开(公告)日:2012-12-27
A photosensitive resin composition and a method for forming patterns by using the same are disclosed. The photosensitive resin composition comprises a novolac resin (A), an ortho-naphthoquinone diazide sulfonic acid ester (B) and a ketol solvent (C). The novolac resin (A) includes a high-ortho novolac resin (A-1) that has ortho-ortho methylene bonding to all methylene bonding in a ratio of 18% to 25%, and a weight ratio (A-1)/(C) of the high-ortho novolac resin (A-1) to the ketol solvent (C) is 0.1 to 2.0, thereby exhibiting excellent temporal stability and further forming patterns with superior film to thickness uniformity and high resolution.