Enzymatic preparation of (1S,2R)- and (1R,2S)-stereoisomers of 2-halocycloalkanols
摘要:
The stereoisomers of cis-2-halocycloalkanols were resolved by a kinetically controlled transesterification with vinyl acetate in the presence of lipases in organic media. High enantioselectivities (ee >98%) and good isolated yields were obtained for all substrates using the appropriate lipase. Burkholderia cepacia lipase was the most efficient enzyme for the resolution of these substrates. The enantiomeric purities of the compounds were defined by derivatization with Mosher's acid and the absolute configurations were determined by chemical correlation. (C) 2012 Elsevier Ltd. All rights reserved.
Comparative study of the vicinal functionalization of olefins with 2:1 bromide/bromate and iodide/iodate reagents
作者:Manoj K. Agrawal、Subbarayappa Adimurthy、Bishwajit Ganguly、Pushpito K. Ghosh
DOI:10.1016/j.tet.2009.01.095
日期:2009.4
halohydrins, halo methyl ethers, and halo acetates from olefins using 2:1 Br−/BrO3− and I−/IO3− reagents. In many cases both reagents afforded products selectively in high yields. The highest halogen atom efficiencies attained were 97% and 93% for Br−/BrO3− and I−/IO3−, respectively. Of the two reagents, I−/IO3− was established to be the preferred reagent for vicinal functionalization of linear alkenes and
Enantioselective Synthesis of Vicinal Halohydrins via Dynamic Kinetic Resolution
作者:Abel Ros、Antonio Magriz、Hansjörg Dietrich、Rosario Fernández、Eleuterio Alvarez、José M. Lassaletta
DOI:10.1021/ol052821k
日期:2006.1.1
[reaction: see text] Expanding the scope of enantioselective catalysis via DKR, transfer hydrogenation of a variety of cyclic alpha-halo ketones was accomplished using the Noyori/Ikariya (R,R)- or (S,S)-I catalysts and either HCO(2)H/Et(3)N or HCO(2)Na/n-Bu(4)NBr in H(2)O/CH(2)Cl(2) as the hydrogen sources. Good yields of vicinal bromo-, chloro-, and fluorohydrins with excellent de and ee levels were
The first organocatalytic enantioselective alpha-bromination of aldehydes and ketones is presented; a C2-symmetric diphenylpyrrolidine catalyst afforded the alpha-brominated aldehydes in good yields and up to 96% ee, while ketones were alpha-brominated by a C2-symmetric imidazolidine in up to 94% ee; furthermore, the organocatalytic enantioselective alpha-iodination of aldehydes is also demonstrated
STEREOCHEMICAL STUDY ON THE REACTION OF COBALOXIME(I) WITH 2-SUBSTITUTED CYCLOHEXYL HALIDES. EVIDENCE FOR AN ELECTRON TRANSFER MECHANISM
作者:Masami Okabe、Masaru Tada
DOI:10.1246/cl.1980.831
日期:1980.7.5
Reaction of cobaloxime (I) , (CoI)−, with 2-hydroxy- (1a and 1b) and 2-alkoxycyclohexyl halides (1c–1h) gave 2-hydroxy- and 2-alkoxycyclohexyl cobaloximes (III) (2 and 3) . Stereochemistry of the organocobaloxime was independent of the configuration of the starting halides. 2-Allyloxycyclohexyl halides (6a and 6b) gave the organocobaloxime having 9-methyl-7-oxabicyclo[4,3,0]nonane moiety. These results
1,2-functionalization of cyclohexane using selenium intermediates
作者:Angelo M. Morella、A.David Ward
DOI:10.1016/s0040-4039(00)98866-x
日期:1985.1
The trans 1,2-phenylseleno acetate, acetamide, alcohol and nitrile of cyclohexane may be oxidized at selenium by halogens and the phenylseleno moiety displaced by halide to give high yields of 1,2 halide-containing products with cis geometry.