Base Induced Chiral Substituted Furans and Imidazoles from Carbohydrate-Derived 2‑Haloenones

Chiral substituted furans and imidazoles are key intermediates to access biologically important molecules. We describe herein a catalyst/ligand free cascade Michael-type addition/intramolecular cyclization/carbohydrate-ring opening of 2-haloenones with 1,3-dicarbonyl compounds or amidines utilizing K2CO3/DMSO at ambient temperature that provides a straightforward approach to a variety of optically active (poly)­hydroxy furans and imidazoles containing multiple stereocenters with good yield and excellent regioselectivity. The furan intermediates provide efficient access to synthetically valuable substituted α-benzyloxyvinyl ketones. The NMR spectrum of the substituted 2-methylfurans shows an unusual long-range (5JH–H) 1H–1H COSY cross-peak between C2–CH3 and C4–H signals.

手性取代呋喃（furan）与咪唑（imidazole）是合成具有重要生物活性分子的关键中间体。本文报道了一种无催化剂/配体的级联反应体系：以碳酸钾（K₂CO₃）/二甲基亚砜（DMSO）为反应介质，在室温条件下实现2-卤代烯酮与1,3-二羰基化合物或脒类化合物的迈克尔加成/分子内环化/糖环开环级联反应，可高效构建一系列兼具多立体中心、光学活性的（多）羟基呋喃与咪唑类化合物，反应收率优良，区域选择性极佳。所得到的呋喃中间体可进一步高效制备具有合成应用价值的取代α-苄氧基乙烯基酮类化合物。在取代2-甲基呋喃的核磁共振氢谱中，C2位甲基（C2–CH₃）与C4位氢（C4–H）信号之间出现了罕见的远程5J_(H-H)耦合的1H-1H COSY交叉峰。