Iron-Catalyzed Rearrangements and Cycloaddition Reactions of 2H-Chromenes
摘要:
Iron(III) salts catalyze the tandem rearrangement/hetero-Diels-Alder reaction of 2H-chromenes to yield tetrahydrochromeno heterocycles. The process can occur as a homodimerization and cycloaddition process using electron-rich dienophiles. Deuterium labeling and mechanistic studies revealed a hydride shift and ortho-quinone methide cycloaddition reaction pathway.
Brønsted acid UiO-66 MOFs were prepared for the efficient homo-dimerization of 2H-chromenes, which involves a tandem rearrangement/hetero-Diels–Alder reaction sequence.
SEM, XRD, FTIR, BET and TGA. An efficient and diastereoselective homo-dimerization of 2H-chromenes catalysis was achieved using the sulfonyl derived MIL-101 MOF as a catalyst. A benzopyranobenzopyran polycyclic structure was generated in high yield and diastereoselectivity under mild catalytic reaction conditions. Furthermore, a regio-isomer was observed when 2H-chromene bears different substitution
Structurally Diverse α-Substituted Benzopyran Synthesis through a Practical Metal-Free C(sp<sup>3</sup>)–H Functionalization
作者:Wenfang Chen、Zhiyu Xie、Hongbo Zheng、Hongxiang Lou、Lei Liu
DOI:10.1021/ol503004a
日期:2014.11.21
A trityl ion-mediated practical C–H functionalization of a variety of benzopyrans with a wide range of nucleophiles (organoboranes and C–H molecules) at ambient temperature has been disclosed. The metal-free reaction has an excellent functional group tolerance and high chemoselectivity and displays a broad scope with respect to both benzopyran and nucleophile partners, efficiently affording a collection