Mechanistic Twist of the [8+2] Cycloadditions of Dienylisobenzofurans and Dimethyl Acetylenedicarboxylate: Stepwise [8+2] versus [4+2]/[1,5]-Vinyl Shift Mechanisms Revealed through a Theoretical and Experimental Study
作者:Yuanyuan Chen、Siyu Ye、Lei Jiao、Yong Liang、Dilip K. Sinha-Mahapatra、James W. Herndon、Zhi-Xiang Yu
DOI:10.1021/ja072203u
日期:2007.9.1
diene moieties of dienylisobenzofurans, the [8+2] reaction occurs through an alternative mechanism involving a [4+2] reaction between the furan moiety of the tetraene and DMAD, followed by a [1,5]-vinyl shift. This computationally predicted novel mechanism was supported experimentally.
最近,据报道,二烯基呋喃和二烯基异苯并呋喃均可与乙炔二羧酸二甲酯 (DMAD) 反应生成 [8+2] 环加合物。了解这些 [8+2] 反应将有助于设计额外的 [8+2] 反应,这些反应具有合成 10 元和更大碳环的潜力。本文旨在通过计算和实验的共同作用,在分子水平上了解最初报道的二烯基异苯并呋喃与炔烃之间[8+2]环加成反应的详细机理。(U)B3LYP/6-31+G(d) 水平的密度泛函理论计算表明,二烯基异苯并呋喃和炔烃之间的协调 [8+2] 途径不受青睐。已经通过计算预测了一种逐步反应途径,包括在二烯基异苯并呋喃和 DMAD 之间形成 [8+2] 反应的两性离子中间体,其中二烯基异苯并呋喃在其二烯部分中含有供电子甲氧基团。该途径与二烯基异苯并呋喃的呋喃部分和 DMAD 之间的 Diels-Alder [4+2] 反应竞争。当二烯基异苯并呋喃的二烯部分中不存在给电子基团时,[8+2] 反