α-Methylene-β-trichloroacetylamino Alkanoates from Trichloroacetimidates of the Baylis-Hillman Adducts
作者:Mario Orena、Roberta Galeazzi、Gianluca Martelli、Samuele Rinaldi
DOI:10.1055/s-2004-831235
日期:——
The Baylis-Hillman adducts 1 were treated with a large amount of CCl3CN in the presence of DBU without solvent to give in good yield the corresponding trichloroacetimidates 5 which by thermal [3.3]sigmatropic rearrangement were converted into the corresponding (E)-2-trichloroacetylaminomethyl-2-propenoates 6, exclusively. On the contrary, when compounds 5 were treated with a catalytic amount of DABCO in dichloromethane, 2-methylene-3-trichloroacetylamino esters 7 were obtained in good yield. Both 5a and 7a underwent iodocyclization, to give a cyclic intermediate precursor of a polyfunctionalized sequence, and the differences in stereoselectivity were in agreement with computational results.
Baylis-Hillman加合物1在无溶剂条件下,与大量CCl3CN和DBU反应,以良好产率得到了相应的三氯乙酰亚胺酸酯5,后者通过热[3.3]σ键迁移重排反应,专一性地转化为相应的(E)-2-三氯乙酰胺甲基-2-丙烯酸酯6。相反,当化合物5在二氯甲烷中与少量DABCO反应时,以良好产率得到了2-亚甲基-3-三氯乙酰胺基酯7。无论是5a还是7a,都发生了碘环化反应,得到了多官能团化序列的环状中间体前驱体,其立体选择性的差异与计算结果相符。