Chemo- and diastereoselective Bi(OTf)3-catalyzed benzylation of silyl nucleophiles
作者:Philipp Rubenbauer、Thorsten Bach
DOI:10.1016/j.tetlet.2007.12.092
日期:2008.2
The direct alkylation of silyl enol ethers with para-methoxybenzylic alcohols or their corresponding acetates was efficiently catalyzed by Bi(OTf)3 in CH3NO2 as the solvent. The reaction provided the α-benzylated carbonylcompounds in high yields after short reaction times using 1–2.5 mol % of the catalyst. Benzylic acetates other than para-methoxybenzylic acetates also underwent the reaction. High
Bi(OTf)3在作为溶剂的CH 3 NO 2中有效地催化了甲硅烷基烯醇醚与对甲氧基苄醇或其相应的乙酸酯的直接烷基化。使用1–2.5 mol%的催化剂,反应在较短的反应时间后即可以高收率得到α-苄基羰基化合物。除对甲氧基苄基乙酸酯以外的乙酸苄酯也进行了反应。用衍生自手性α-支化对-甲氧基苄醇的乙酸酯观察到高的非对映选择性。另外,据报道用Et 3 SiH作为还原剂进行催化还原。
A Highly Chemoselective Reduction of Conjugated Nitro Olefins with Hantzsch Ester in the Presence of Silica Gel
作者:Masayuki Fujii
DOI:10.1246/bcsj.61.4029
日期:1988.11
An effective system to reduce conjugated nitro olefins into the corresponding nitroalkanes is described. The system composed of Hantzsch ester (HEH) and silica gel in benzene exerts high yield and excellent chemoselectivity under almost neutral conditions. Facile applications of the system to the syntheses of natural products are also described.
Gold(III) Chloride-Catalyzed Diastereoselective Alkylation Reactions with Chiral Benzylic Acetates
作者:Philipp Rubenbauer、Thorsten Bach
DOI:10.1002/adsc.200700600
日期:2008.5.5
Gold(III) chloride was shown to be an efficient catalyst for the diastereoselective CC bond formation of various chiral para-methoxybenzylic acetates and different nucleophiles. All electrophilic acetates carried next to the reacting center a stereogenic carbon center bound to a functional group (FG), a methyl substituent and a proton. Selectivities were good (dr>80/20) in favor of the anti-product
氯化金(III)被证明是形成各种手性对甲氧基苄基乙酸酯和不同亲核试剂的非对映选择性CC键的有效催化剂。所有亲电子的乙酸酯在反应中心附近均带有与官能团(FG),甲基取代基和质子键合的立体碳中心。选择性好(dr > 80/20),对于FG = COOMe,NO 2和CN有利于产生反产物,对于FG = SO 2 Et,PO(OEt)2有利于合成产物。反应最有可能通过一种游离碳正离子,其中优选的构象可促进面部分化。几种芳烃亲核试剂显示与催化条件兼容,可提供高收率的相应取代产物(13个实例,占62-98%)。此外,其他亲核试剂(烯丙基三甲基硅烷,三甲基甲硅烷基氰化物,2,2-二甲基-3-(三甲基甲硅烷基氧基)丁烷,对甲苯磺酰胺和乙酰丙酮)与代表性手性亲电子试剂以高产率和非对映选择性的方式反应。
Inter- and intramolecular [4 + 2] cycloadditions of nitroalkenes with olefins. 2-Nitrostyrenes
作者:Scott E. Denmark、Brenda S. Kesler、Young Choon Moon
DOI:10.1021/jo00044a029
日期:1992.8
Aromatic nitroalkenes 9-12 underwent Lewis acid catalyzed cycloadditions with various cyclic alkenes to afford high yields of nitronates 25-30 with exclusive anti selectivity. Hammett studies helped to further delineate the role of the Lewis acid. Reaction of nitroalkenes 8 and 10 with various cyclic dienes in the presence of a Lewis acid demonstrated the ability of nitroalkenes to behave as dienes in cycloadditions. The major products were the syn diastereomers which arise from an endo-folded transition structure. Finally, intramolecular cycloaddition of 36-39 allowed a correlation between the stereochemical course of the reaction and positions of sp2 centers in the tether to be addressed.
Preparation of diverse BODIPY diesters
作者:Sewwandi Abeywardana、Annabelle L. Cantu、Teodora Nedic、Michael P. Schramm
DOI:10.1016/j.tetlet.2018.07.054
日期:2018.9
The synthesis and properties of a variety of substituted BODIPY diesters is presented. We find that certain substitution patterns afford appreciable yields of the target compounds and that electronic effects result in predicable differential fluorescent behavior. Challenges to further water solubilize these dyes and/or provide new points of attachment for biological tagging remain, these strategies