imidazole, which then reacts with a π-allyl palladium electrophile generated from an allylalcohol derivative by a palladium-based catalyst. A broad scope of substrates was suitable for this reaction. The utility of this method was demonstrated by a gram-scale reaction and subsequent elaboration of the allylation products.
Here, we report a catalytic methodology for the enantioselectivesynthesis of α-chiral 1,3-difunctionalized BCPs from a three-component coupling of [1.1.1]propellane, a Grignard reagent, and an allylic phosphate. The reaction proceeds via the addition of the Grignard reagent to [1.1.1]propellane followed by an asymmetric N-heterocyclic carbene (NHC)-catalyzed allylicsubstitution of the resulting BCP–Grignard
Stereospecific Synthesis of Bicyclic β-Lactams via Metal-Catalyzed Carbonylative Coupling and Cyclization Reactions
作者:Zhongxin Zhou、Howard Alper
DOI:10.1021/jo9517104
日期:1996.1.1
Bicyclic beta-lactams were synthesized by the carbonylative coupling and cyclization reaction of 2-aryl-1,3-thiazines with allyl phosphates, catalyzed by bis(benzonitrile)palladium dichloride, using N,N-diisopropylethylamine as a base in tetrahydrofuran. Several rhodium complexes were also effective for this process. These transformations are stereospecific, with the aryl and vinyl groups on the beta-lactam ring being cis to each other. This methodology provides a novel route for the preparation of the cepham analogs, cis-7-vinyl-5-thia-1-azabicyclo[4.2.0]octan-8-ones.
Intermolecular Metallo-ene Reaction Catalyzed by Palladium
作者:Youval Shvo、Anan Haj Ichia Arisha
DOI:10.1021/jo001028w
日期:2001.7.1
Total Synthesis of Crystalline (.+-.)-Fredericamycin A. Use of Radical Spirocyclization
作者:Derrick L. J. Clive、Yong Tao、Ahmad Khodabocus、Yong-Jin Wu、A. Gaetan Angoh、Sharon M. Bennett、Christopher N. Boddy、Luc Bordeleau、Dorit Kellner
DOI:10.1021/ja00104a009
日期:1994.12
Crystalline (+/-)-fredericamycin A (1) was synthesized using, as a key step, 5-exo-digonal radical closure of selenide 55. The selenide was generated from the corresponding ketone 54, itself assembled from two components: aldehyde 29 and bromonaphthalene 48. The product of the radical cyclization (56) was converted into spiro diketone 59, and the pentadienyl chain was then formed by a Wittig reaction. Selective deprotection of ring A was accompanied by isomerization of the diene system to the required E,E geometry, and treatment with boron tribromide, followed by aqueous hydrolysis in the presence of air, effected selective demethylation and oxidation to (+/-)-1. The radical spirocyclization used in this synthesis is a general method.