Radical Philicity Inversion in Co- and Fe-Catalyzed Hydrogen-Atom-Transfer-Initiated Cyclizations of Unsaturated Acylsilanes
作者:Bin Wu、Rong Zhu
DOI:10.1021/acscatal.9b04774
日期:2020.1.3
hydrogen-atom-transfer reactions involving unsaturated acylsilanes. Guided by the same concept, we have explored two transformations, namely, a Co-catalyzed cycloisomerization reaction and a Fe-catalyzed cyclization/Giese addition reaction. Both reactions involve the generation of a versatile α-siloxy radical intermediate via concomitant philicity inversion and radical translocation, which is mechanistically
Enantio- and Diastereoselective Tandem Zn-Promoted Brook Rearrangement/Ene−Allene Carbocyclization Reaction
作者:Rozalia Unger、Fritz Weisser、Nicka Chinkov、Amnon Stanger、Theodore Cohen、Ilan Marek
DOI:10.1021/ol9004036
日期:2009.4.16
The zinc-catalyzed addition of various alkynes to acylsilanes followed by a Zn−Brook rearrangement and either the Zn−ene−allene or Zn−yne−allene cyclization led to the enantio- and diastereoselective formation of carbocycles in a single-pot operation.
Treatment of chlorobis(methyldiphenylsilyl)methyllithium with various alkyl and aryl Grignard reagents and CuCN center dot 2LiCl afforded 1,1-disilylalkylcopper species. The aerobic oxidation of the resulting copper reagents provided a variety of acylsilanes in good yields. Meanwhile, treatment of dichloro(methyldiphenylsilyl)methyllithum with Bu2CuLi center dot LiCN provided 1-cyano-1-silylalkylcopper species via consecutive double 1,2-migration of alkyl and cyano groups. (c) 2005 Elsevier Ltd. All rights reserved.
Facile Synthesis of Acylsilanes via Aerobic Oxidation of <i>g</i><i>em-</i>Disilylalkylcopper Compounds
5-Exo cyclizations of primary and secondary radicals with acylsilanes successfully give cyclopentyl silyl ethers. The corresponding 6-exo cyclizations are sensitive to changes of the size of silyl groups. Secondary radicals undergo 6-exo cyclizations with acylsilanes more slowly. Reaction of aryl radical with acylsilane proceeds well for 5-exo cyclization but not for 6-exo cyclization. Vinyl radicals give best results in 5-exo cyclizations with acylsilanes but give low yields (similar to 30%) in 6-exo cyclizations. Intramolecular cyclizations of vinyl radicals with acylsilanes give enol silyl ethers regiospecifically.