Reduction of Li2MnCl4 with magnesium metal provided activated manganese as a black suspension in THF. Treatment of organichalides such as allyl bromides, α-halo esters or aryl halides with activated manganese furnished various organomanganese reagents which reacted further with electrophiles to afford the corresponding adducts. The reaction of a ketone bearing an iodoaryl moiety with this active manganese
(R)-(+)-N-Methylbenzoguanidine ((R)-NMBG) catalyzed acylative kinetic resolution of racemic 3-hydroxy-3-aryl-propanoates
作者:Akira Yamada、Kenya Nakata
DOI:10.1016/j.tetlet.2016.09.014
日期:2016.10
cyclohexane carboxylic anhydride under mild reaction conditions. A tert-butyl ester moiety is necessary to achieve a high selectivity. The effects of the substituents on the aromatic rings of the substrates were systematically investigated, and diverse substrates participated in the reaction with good s-values (>20) irrespective of the type of substituents and their patterns, except for o-methoxy group
The aldol reaction of several aldehydes with silyl enol ethers proceeded smoothly to give the corresponding aldols in good to high yields at −78 °C by using 1.0 mol% of a novel cationic species with tetrakis(pentafluorophenyl)borate anion.
Various beta-lactones were prepared from beta-hydroxycarboxylic acids by intramolecular dehydration condensation using MNBA, an effective coupling reagent, along with a nucleophilic catalyst. The transition state that provides the desired 4-membered ring model system is disclosed by density functional theory (DFT) calculations, and the structural features of the transition form are discussed. This method was successfully applied to the asymmetric total synthesis of tetrahydrolipstatin (THL), an antiobestic drug used in clinical treatment to inhibit the activity of pancreatic lipase.
A Facile and Efficient Direct Aldol Addition of Simple Thioesters
作者:Julianne M. Yost、Guoqiang Zhou、Don M. Coltart
DOI:10.1021/ol060413q
日期:2006.3.1
Simple thioesters undergo direct aldol addition to aldehydes in the presence of MgBr2.OEt2 and i-Pr2NEt using untreated, reagent-grade CH2Cl2 under atmospheric conditions. The reactions proceed extremely rapidly and in excellent yield.