Air-stable and recyclable, the CuII -(bis)oxazoline complex 1 efficiently catalyzes diastereo- and enantioselective hetero-Diels-Alder reactions between β,γ-unsaturated α-keto acid derivatives 2 and vinyl ethers for the synthesis of substituted dihydropyrans 3 [Eq. (1)]. Results of the crystalstructure analysis of 1 in combination with calculations on model compounds indicate the formation of a reactive
Cu II-(双)恶唑啉络合物1空气稳定且可回收,可有效催化β,γ-不饱和α-酮酸衍生物2和乙烯基醚之间的非对映和对映选择性杂Diels-Alder反应,用于合成取代的二氢吡喃3 [等式 (1)]。1的晶体结构分析结果与对模型化合物的计算相结合,表明通过用螯合底物取代两个H 2 O配体,形成了反应性中间体。X = OEt,N(OMe)Me;R =烷基,芳基,烷氧基,硫代苄基。
Enantioselective Synthesis of Dihydropyrans. Catalysis of Hetero Diels−Alder Reactions by Bis(oxazoline) Copper(II) Complexes
作者:David A. Evans、Jeffrey S. Johnson、Edward J. Olhava
DOI:10.1021/ja992175i
日期:2000.3.1
C2-symmetric bis(oxazoline)−Cu(II) complexes 1 and 2 catalyze the inverse electron demand hetero Diels−Alder reaction of α,β-unsaturated carbonyl compounds (heterodiene) with electron-rich olefins (heterodienophile) in high diastereo- and enantioselectivity. α,β-Unsaturated acyl phosphonates and β,γ-unsaturated α-keto esters and amides are effective heterodienes, while enol ethers and sulfides function
Activated 1-alkenes such as ketene dithioacetals, vinyl sulfides, N-vinyl amides, and N-vinylcarbazole react with oxalyl chloride or ethoxalyl chloride in the presence of pyridine to give the 2-oxo-3-alkenoic acids or ethyl esters, respectively.