A [3+2] Cyclization of Siloxyalkynes and Isocyanides for the Synthesis of Oxazoles
作者:An Wu、Jianwei Sun
DOI:10.1055/s-0037-1610402
日期:2019.3
A mild and efficient [3+2] cyclization of siloxyalkynes for the synthesis of aromatic heterocycles is developed. It is a new addition to the cyclization reactions of these versatile species. In the presence of TBAF as promoter, siloxyalkynes react with electron-withdrawing isocyanides to form a range of oxazole products. In this reaction, siloxyalkynes contribute the C–O unit for the cyclization, which
Synthesis of Eight‐Membered Lactams through Formal [6+2] Cyclization of Siloxy Alkynes and Vinylazetidines
作者:An Wu、Qiang Feng、Herman H. Y. Sung、Ian D. Williams、Jianwei Sun
DOI:10.1002/anie.201902866
日期:2019.5.13
lactams through formal [6+2] cyclization of siloxyalkynes and vinylazetidines has been developed. Evidence from a chirality transfer experiment suggests that the reaction proceeds via a [3,3]‐sigmatropic rearrangement from a ketene intermediate. This insight led to the development of alternative conditions and use of acyl chlorides as ketene precursors for the [6+2] reaction with vinylazetidines.
Formal [4 + 4]-, [4 + 3]-, and [4 + 2]-cycloaddition reactions of donor–acceptor cyclobutenes, cyclopropenes and siloxyalkynes induced by Brønsted acid catalysis
作者:Haifeng Zheng、Rui Wang、Kan Wang、Daniel Wherritt、Hadi Arman、Michael P. Doyle
DOI:10.1039/d1sc00158b
日期:——
Brønsted acid catalyzed formal [4 + 4]-, [4 + 3]-, and [4 + 2]-cycloadditions of donor–acceptor cyclobutenes, cyclopropenes, and siloxyalkynes with benzopyrylium ions are reported. [4 + 2]-cyclization/deMayo-type ring-extension cascade processes produce highly functionalized benzocyclooctatrienes, benzocycloheptatrienes, and 2-naphthols in good to excellent yields and selectivities. Moreover, the optical
An unusual formal migrative cycloaddition of aurone-derived azadienes: synthesis of benzofuran-fused nitrogen heterocycles
作者:Qiang Feng、An Wu、Xinhao Zhang、Lijuan Song、Jianwei Sun
DOI:10.1039/d1sc00941a
日期:——
direct [4 + n] cycloadditions owing to their s-cis conformation as well as the thermodynamically favored aromatization nature of these processes. However, distinct from this common reactivity, herein we report an unusual formal migrative annulation with siloxy alkynes initiated by [2 + 2] cycloaddition. Unexpectedly, this process generates benzofuran-fused nitrogen heterocyclicproducts with formal substituent