Mild Oxidative Bromination of Alkenes and Alkynes with Zinc Bromide and Lead Tetraacetate
作者:Hussni A. Muathen
DOI:10.1081/scc-200031007
日期:2004.1.1
Abstract Zinc bromide and lead tetraacetate is a practical and safe source of bromine. The combined reagents are used to brominate a variety of alkenes to vicinal dibromoalkanes. Similarly, alkynes can be converted into dibromoalkenes in high yields. The reagents are also capable of tetrabromination of alkynes.
Enantioselective Preparation of Benzimidazole Derivatives and Their Salts
申请人:Jiang Biao
公开号:US20080319195A1
公开(公告)日:2008-12-25
The invention relates to a new process for preparing benzimidazole derivatives having a chiral sulfoxide group in enantiomerically pure form or in a form in which one of the two enantiomers is present in an increased quantity over the other enantiomer. The invention likewise relates to a process for preparing the salts of the individual enantiomers of the benzimidazole derivatives with a chiral sulfoxide group. The invention relates in particular to a process for preparing the S-enantiomer of omeprazole (also known as esomeprazole) and the salts thereof, more particularly the zinc salt of the S-enantiomer of omeprazole. In the new process a prochiral sulfide is oxidized in an organic solvent with an oxidizing agent in the presence of a titanium(IV) complex.
Sequential bromination reactions from beads with methyltriphenylphosphonium tribromide groups
作者:Rodrigo Cristiano、Andrew D. Walls、Richard G. Weiss
DOI:10.1002/poc.1694
日期:——
A reusable bromination reagent based on polystyrene beads with covalently appended methyltriphenylphosphoniumtribromidegroups has been developed. The results frombrominationreactions of several structurally diverse unsaturated substrates with the beads and with solutions of a non‐polymeric model brominating reagent, methyltriphenylphosphoniumtribromide, are described. It is shown that the reactions
The effect of vicinyl olefinic halogens on cross-coupling reactions using Pd(0) catalysis
作者:Michael G. Organ、Haleh Ghasemi、Cory Valente
DOI:10.1016/j.tet.2004.08.006
日期:2004.10
products reliably under all reaction conditions. Compound 5 did not provide cross coupled products under any of the reaction conditions used. The Negishi reaction was the only one that worked for templates 4 and 11. Studies indicate that oxidative addition of the most reactive carbon–halogenbond to Pd(0) is followed by elimination of the second halide, when the second halide is a bromide or an iodide