已经开发出一种通过硫醇触发的串联迈克尔加成/分子内亨利反应对 2-硝基苯并呋喃进行有效脱芳环化的方法。一系列硫代苯并[3,2- b ]苯并呋喃-11-醇和四氢噻吩并[3,2- b ]苯并呋喃-3-醇的产率高达 99%,dr 高达 >20:1。 2-硝基苯并呋喃与2-巯基苯甲醛通过串联脱芳香迈克尔加成/分子内亨利反应/重芳香化/氧化脱氢一锅两步操作制备有价值的硫色酮稠合苯并呋喃。初步提出了该反应的机理。
An Improved Synthesis of 2-Nitrobenzo[<i>b</i>]furans
作者:Anne Tromelin、Pierre Demerseman、René Royer
DOI:10.1055/s-1985-31435
日期:——
2-Nitrobenzo[b]furans 4 are prepared in improved yields by reacting o-hydroxybenzaldehydes 1 and bromonitromethane (2) at low temperature in order to avoid the dehydration of the aldol intermediate 3 in the alkaline condensation medium. This aldol 3 is then quantitatively dehydrated by heating in acetic anhydride.
phosphine-catalyzed asymmetric dearomative [3+2] cycloaddition of 2-nitrobenzofurans with aldehyde-derived Morita–Baylis–Hillman (MBH) carbonates or allenoate was developed. The reaction with MBH carbonates resulted in a series of cyclopentabenzofurans containing three contiguous stereocenters with good to high yields, diastereoselectivities and enantioselectivities. The use of allenoate also gave the target product
A straight synthetic approach to fused polycyclic tropane scaffold formation through an asymmetric dearomatization cycloaddition process of 2-nitrobenzofurans with cyclic azomethineylides was successfully developed. In the presence of a chiral copper complex, derived from Cu(OAc)2 and a diphosphine ligand, a series of fused polycyclic tropane derivatives were obtained in high yields (75-91%) with
An efficient Ph2PMe-catalyzed dearomative (3 + 2) annulation of 2-nitrobenzofurans, 2-nitrobenzothiophenes, and 3-nitrobenzothiophenes with allenoates has been developed. With the developed protocol, a series of structurally important cyclopenta[b]benzofurans and cyclopenta[b]benzothiophenes were obtained in good to excellent yields (up to 98%) under mild conditions. In addition, preparative-scale