C−C versus C−O Anionic Domino Cycloalkylation of Stabilized Carbanions: Facile One-Pot Stereoselective Preparation of Functionalized Bridged Bicycloalkanones and Cyclic Enol Ethers
cycloalkylation, to synthetically valuable monocyclic or fused polycyclic functionalized enolethers of high synthetic value. Semiempirical calculations showed a small difference in energy and the late character of the transition states leading to cis and trans isomers of the corresponding fused polycyclic enolethers. These results, although minimizing the influence of a destabilizing 1,3-interaction
α,α'-双活化环状或无环酮经历化学选择性碱促进(K2CO3,DBU)一锅 CC 环烷基化,1,3- 和 1,4-二卤化物具有顺式固定构型。该反应产生高度官能化的双环 [3.2.1]octan-9-one 和双环 [4.2.1]nonan-9-one 衍生物,它们很容易通过高产率逆狄克曼裂解转化为七元和八元环. 从反式-1,4-二溴-2-丁烯开始,该转化受立体电子因素的控制,并通过化学和立体选择性的 CO 环烷基化,导致具有合成价值的单环或稠合多环官能化烯醇醚具有高合成价值。半经验计算显示能量的微小差异和导致相应稠合多环烯醇醚顺式和反式异构体的过渡态的后期特征。这些结果虽然最大限度地减少了不稳定的 1,3-相互作用对反应结果的影响,但在质量上与实验结果一致。
Stereoselective Synthesis of Alkenyl alpha,alpha'-Bridged Bis(glycines) using Palladium Promoted Substitution in the Bridge.
作者:Jon Efskind、Tore Benneche、Kjell Undheim、Steinar Husebye、Jose Maria Moreno、Antonio Romerosa、Ward T. Robinson、Björn O. Roos、Claire Vallance、Bryan R. Wood
DOI:10.3891/acta.chem.scand.51-0942
日期:——
Conformationally constrained cystine analogues have been synthesized which have an unsaturated four-carbon backbone-chain as a bridge between the alpha,alpha'-positions in two glycine units. Stereoselective synthesis of the cis and trans isomers of bis(glycines) with a 2'-butene bridge, and their 2'-bromo derivatives, is described. Palladium mediated coupling between the bromides and stannanes provided for carbo-substitution at the olefinic carbon in the bridge. N-Methyl-2-pyrrolidinone was an excellent solvent for this reaction when triphenylarsine was the ligand for palladium. Mild hydrolytic conditions furnished the methyl esters of the C-4-bridged bis(glycine) derivatives.
BADER, HUBERT;HOPF, HENNING;SIEPER, KERSTIN, CHEM. BER., 122,(1989) N, C. 383-384