synthesize metastable bicyclic 2,5‐dihydrooxepines from cyclic 1,3‐diketones and 1,4‐dibromo‐2‐butenes through the retro‐Claisen rearrangement of syn‐2‐vinylcyclopropyl diketone intermediates is reported. DFT calculations were performed to understand the reaction selectivity and mechanisms towards [1,3]‐ or [3,3]‐sigmatropic rearrangements, highlighting the crucial influence of the temperature. The reaction
Iodine‐catalyzed ring opening of 1,1‐diacylcyclopropanes for synthesis of fully substituted pyrazole derivatives have been reported. This reaction tolerates a broad range of cyclopropyl ketones and sulfonyl hydrazides to afford useful and densely functionalized pyrazole derivatives with a hydroxy functional group.
Bromine Radical Catalysis by Energy Transfer Photosensitization
作者:Dian-Feng Chen、Cameron H. Chrisman、Garret M. Miyake
DOI:10.1021/acscatal.0c00281
日期:2020.2.21
user-friendly bromine radical catalysis system that enables efficient [3 + 2] cycloaddition of diversely substituted vinyl- and ethynylcyclopropanes with a broad range of alkenes, including drug-like molecules and pharmaceuticals. Key to the success is the use of photosensitizing triplet-state β-fragmentation of a judiciously selected precatalyst, cinnamyl bromide, to generate bromine radicals in a
An organocatalytic Cloke–Wilson rearrangement of cyclopropyl ketones to 2,3-dihydrofurans is exploited utilizing the homoconjugate addition process. With 1,4-diazabicyclo[2.2.2]octane as the catalyst, the rearrangement in DMSO at 120 °C proceeded in generally high yields, exclusive regioselectivity, and a broad substrate scope. An examination of the mechanism including stereochemical analysis and intermediate
We report a phosphine‐catalyzed activation of electron‐deficient vinylcyclopropanes (VCPs) to generate an ambident C5 synthon that is poised to undergo consecutive reactions. The utility of the activation is demonstrated in a phosphine‐catalyzed rearrangement of vinylcyclopropylketones to cycloheptenones in good yields with a broad substrate scope. Mechanistic investigations support a stepwise process