has been developed from the cyclization of 2‐propynyl‐1,3‐dicarbonyl compoundscatalyzed by potassium tert‐butoxide, copper(II) trifluoromethanesulfonate and triphenylphosphine using methanol/dichloromethane as the solvent under very mild conditions. Moreover, dihydrofurans could be easily transformed into the corresponding furans in the presence of trifluoroacetic acid.
Controllable Access to Furans and Dihydrofurans through Cyclization/Coupling of Internal Acetylenic β‐Ketoesters with Aryl Bromides
作者:Bartosz Bisek、Wojciech Chaładaj
DOI:10.1002/adsc.202200686
日期:2022.12.20
Pd-catalyzed tandem cyclization/coupling of internal β-propargylic-β-ketoesters with (hetero)aryl bromides is described. Two protocols are established which selectively lead to 2-benzylidene-dihydrofurans, when isomerization is inhibited under mild conditions (temp. ≤40 °C and weak base – K2CO3), or to 2-benzyl-furans when base-induced aromatization is enabled. A catalytic cycle involving oxidative
描述了 Pd 催化的内部 β-炔丙基-β-酮酯与(杂)芳基溴化物的串联环化/偶联。建立了两种方案,当异构化在温和条件下(温度≤40 °C 和弱碱 – K 2 CO 3)被抑制时,选择性地产生 2-亚苄基-二氢呋喃,或在碱诱导芳构化时产生 2-苄基-呋喃已启用。基于详细的实验和理论研究,提出了涉及氧化加成、用炔取代溴化物、限速反选择性5-exo-dig氧环化随后氧鎓中间体快速去质子化和还原消除的催化循环。
Access to 2-Alkenyl-furans via a Cascade of Pd-Catalyzed Cyclization/Coupling Followed by Oxidative Aromatization with DDQ
作者:Bartosz Bisek、Wojciech Chaładaj
DOI:10.1021/acs.joc.4c00149
日期:2024.5.17
An unprecedented DDQ-mediated oxidative aromatization of 2-bezylidene-dihydrofurans yielding 2-alkenyl-furans is disclosed. Integration of this transformation with a prior Pd-catalyzed reaction of α-propargylic-β-ketoesters and (hetero)aryl halides into a one-pot cascade process opens a direct modular route to highly substituted 2-vinyl-furans. Experimental and computational studies reveal that the