A Resource-Efficient and Highly Flexible Procedure for a Three-Component Synthesis of 2-Imidazolines
摘要:
A multicomponent reaction between alpha-acidic isonitriles, primary amines, and carbonyl compounds was studied using 14 different solvents. Depending on the isocyanide that was used, optimal yields for the three-component synthesis of 2H-2-imidazolines were observed in different solvents. The solvents could be used as purchased, and in situ preformation of the imine was not required. By selecting the appropriate solvent, it was possible to considerably expand the range of compatible isocyanides toward less alpha-acidic isocyanides. Further process simplification was achieved by performing the reaction at higher concentrations and avoiding purification by column chromatography, resulting in a fast, easy to perform, and resource-efficient protocol for this three-component reaction.
Enantioselective cyclization of α-isocyano esters with azodicarboxylates catalyzed by FeIIâN,Nâ²-dioxide complexes has been developed. Under mild conditions, a variety of 1,2,4-triazoline derivatives was obtained in high yields and enantioselectivities.
The Synthetic Intermediate of Pyridoxine. II. The Thermal Cyclization of Ethyl α-Isocyanopropionate to 5-Ethoxy-4-methyloxazole
作者:Itsutoshi Maeda、Kazushi Togo、Ryonosuke Yoshida
DOI:10.1246/bcsj.44.1407
日期:1971.5
product, II, was 20%; unreacted I (30%), ethyl α-cyanopropionate(20%), and dimer of I (5%) were also obtained. The α-hydrogen of ethyl α-isocyanosuccinate (X) can be more easily removed than that of I, so X may be expected to be more readily converted to 5-ethoxy-4-ethoxycarbonylmethyloxazole (XI), which is also an intermediate of pyridoxine. The yield of XI from X did not exceed 30% because of the
α-异氰基丙酸乙酯 (I) 热环化生成 5-乙氧基-4-甲基恶唑 (II) 作为合成吡哆醇的中间体。也进行了几种新的α-异氰基羧酸烷基酯与相应的5-烷氧基-4-取代的恶唑的类似反应。研究了I的热环化反应产物。180℃环化5小时,主产物II的最大收率为20%;还得到了未反应的 I (30%)、α-氰基丙酸乙酯 (20%) 和 I 的二聚体 (5%)。α-异氰基琥珀酸乙酯 (X) 的 α-氢比 I 更容易去除,因此可以预期 X 更容易转化为 5-乙氧基-4-乙氧基羰基甲基恶唑 (XI),它也是吡哆醇。
A Facile Procedure for the Synthesis of<i>N</i>-Formyl Amino Acid Esters
作者:T. Chancellor、Charles Morton
DOI:10.1055/s-1994-25628
日期:——
A variety of amino acid ester hydrochlorides react with triethyl orthoformate (TEOF) or trimethyl orthoformate (TMOF) to give the N-formyl amino acid ester in good yield and high optical purity.
Chiral trans-carboxylic trifluoromethyl 2-imidazolines by a Ag2O-catalyzed Mannich-type reaction
作者:Laura Trulli、Fabio Sciubba、Stefania Fioravanti
DOI:10.1016/j.tet.2017.12.029
日期:2018.2
Trifluoromethyl aldimines derived from α-amino esters have proven to be very good starting materials to obtain the title compounds. A Ag2O-catalyzed Mannich-type/cyclization cascade reaction starting from suitable α-isocyano acetates leads to enantiopure valuable trans-carboxylic trifluoromethyl substituted 2-imidazolines by a highly stereoselective addition without the need to add organocatalysts