22711-52-0Relevant articles and documents
TEMPO-Regulated Regio- and Stereoselective Cross-Dihalogenation with Dual Electrophilic X+ Reagents
Kong, Yi,Cao, Tongxiang,Zhu, Shifa
supporting information, p. 3004 - 3010 (2021/08/23)
A TEMPO catalyzed cross-dihalogenation reaction was established via redox-regulation of the otherwise complex system of dual electrophilic X+ reagents. Formally, the ICl, BrCl, I2 and Br2 were generated in-situ, which enabled high regio- or stereoselective access to a myriad of iodochlorination, bromochlorination and homo-dihalogenation products with a wide spectrum of functionalities. With its mild conditions and operational simplicity, this method could enable wide applications in organic synthesis, which was exemplified by divergent synthesis of two pharmaceuticals. Detailed mechanistic investigations via radical clock reaction, pinacol ring expansion and Hammett experiments were conducted, which confirmed the intermediacy of halonium ion. In addition, a dynamic catalytic model based on the versatile catalytic role of TEMPO was proposed to explain the selective outcomes.
Visible-light photoredox catalysis: Dehalogenation of vicinal dibromo-, α-halo-, and α,α-dibromocarbonyl compounds
Maji, Tapan,Karmakar, Ananta,Reiser, Oliver
supporting information; experimental part, p. 736 - 739 (2011/03/20)
vic-Dibromo-, α-halo-, or α,α-dibromocarbonyl compounds can be efficiently dehalogenated using catalytic tris(2,2′-bipyridyl) ruthenium dichloride (Ru(bpy)3Cl2) in combination with 1,5-dimethoxynaphthalene (DMN) and ascorbate as sacrificial electron donor. For this process, a visible light promoted photocatalytic cycle is proposed that involves the reduction of carbon halogen bonds via free radical intermediates.
Palladium-mediated cross-coupling reactions involving 3-substituted alkyl (E)-2,3-dibromopropenoates and arylzinc or aryltin derivatives
Rossi, Renzo,Bellina, Fabio,Carpita, Adriano,Mazzarella, Felice
, p. 4095 - 4110 (2007/10/03)
Stereodefined unsymmetrically 3,3-disubstituted alkyl 2-bromopropenoates, 5, were regioselectively prepared by Pd-mediated reactions between 3-alkyl, 3-aryl and 3-alkoxycarbonyl substituted (E)-2,3-dibromopropenoates, (E)-7, and aryl or 1-alkynylzinc chlorides. The stereospecificity of these reactions was found to be dependent on the type of substituent present in the 3-position of (E)-7. The (E)-stereochemistry of compounds 5b, 5d and 5i so prepared was confirmed by their conversion into the corresponding 4-substituted 3-bromocoumarins. Tetrasubstituted α,β-unsaturated esters 10 were then synthesized by Pd-mediated reactions either of (E)-7 with a molar excess of an arylzinc chloride or an aryltributylstannane, or of a compound of general formula 5 with an aryltributylstannane. An examination of the parameters which influence the stereochemistry and the yields of these arylations was made.
