19781-77-2Relevant academic research and scientific papers
Ring closing metathesis and metal-catalyzed cyclopropanation for the preparation of sultone derivatives
Ali, Korany A.,Metz, Peter
, p. 19 - 29 (2019/04/17)
Ring closing metathesis (RCM) using Grubbs catalyst 2nd generation as a catalyst was applied to prepare series of novel unsaturated sultones with high yields. Many attempts, were applied for the cyclopropanation of the allylic sultones by Simmon-smith cyclopropanation using diethyl zinc/diiodomethane or Zn-Cu/diiodomethane but in each case the corresponding cyclic adduct was not formed. A novel palladium or preferably rhodium-catalyzed cyclopropanation of unsaturated sultones with ethyl diazoacetate was achieved by the transition metal-catalyzed transfer of a CH-CO2Et unit. The reaction was applied by a portion-wise addition of ethyl diazoacetate over 6h to a mixture of the sultones and palladium(II) acetate or rhodium(II) acetate dimer under low temperature (0-20 o C). The desired products of the cyclopropanation were achieved in each case, as a single diastereomer with 33- 37% yield in the allylic sultones and 10% for vinylic sultone.
Assignment of absolute configuration of natural abundance deuterium signals associated with (R)- and (S)-enantioisotopomers in a fatty acid aligned in a chiral liquid crystal: Enantioselective synthesis and NMR analysis
Baillif, Vincent,Robins, Richard J.,Billault, Isabelle,Lesot, Philippe
, p. 11180 - 11187 (2007/10/03)
Previous experimental natural abundance deuterium (NAD) NMR results have shown an odd/even-related alternation in the (2H/1H) ratio of the methylene groups of fatty acids (ChemBioChem 2001, 2, 425) and, by NAD NMR in CLC, a marked difference between enantiotopic deuterons for each methylenic site (Anal. Chem. 2004, 76, 2827). However, to date, the assignment of the absolute configuration for each deuterium has not been possible. To investigate further the origin of these effects, the assignment of NAD quadrupolar doublets observed in chiral oriented solvent is required. Here we describe the assignment of R- and S-isomers resulting from the isotopic substitution in positions 4 and 5 in the aliphatic chain of 1,1′- bis(thiophenyl)hexane 1 (BTPH) derived from natural linoleic acid of plant origin. This was achieved using an optimized synthetic strategy to obtain separately four regio- and stereoselectively deuterated enantiomers of BTPH. By reference to the deuterium spectra of these isotopically labeled reference compounds, we demonstrate that, on both 4 and 5 positions of BTPH, the isotopic enantiomers of S configuration are depleted relative to those of R configuration. This finding effectively explains the observed low ( 2H/1H) ratio in NAD of some ethylenic sites of unsaturated fatty acids.
Catalyzed Enantioselective Alkylation of Aldehydes
Bolm, Carsten,Schlingloff, Gunther,Harms, Klaus
, p. 1191 - 1204 (2007/10/02)
Enantioselective alkylation of a variety of aldehydes with diethylzinc was achieved by using catalytic amounts of optically active pyridines and C2-symmetric 2,2'-bipyridines.The products were obtained in good yields with high enantioselectivit
CYCLIZATION OF AMINYL RADICALS GENERATED BY ANODIC OXIDATION OF LITHIUM ALKENYLAMIDES. STEREO- AND REGIOSELECTIVE SYNTHESIS OF cis-1-ALKYL-2,5-DISUBSTITUTED PYRROLIDINES
Tokuda, Masao,Yamada, Yasufumi,Takagi, Toshiya,Suginome, Hiroshi,Furusaki, Akio
, p. 281 - 296 (2007/10/02)
Neutral aminyl radicals (3) generated by anodic oxidation of lithium alkenylamides (2) were found to undergo a stereo- and regioselective cyclization to give cis-1-alkyl-2,5-disubstituted pyrrolidines (5c-5h) in moderate yields.The cis stereochemistry of 5c-5h was confirmed by comparison with the corresponding trans-1-alkyl-2,5-disubstituted pyrrolidines which were prepared by aminomercuration of 1c-1h.The structure of trans-1,2-dimethyl-5-phenylpyrrolidine (17) was established by an X-ray crystallographic analysis of its ammonium bromide 21.Various aminyl radicals examined in this study were found to combine exclusively with the internal carbon of their double bond to give a five- (5a-5h) or six-membered ring (13).No product arising from the cyclization is obtained from N-methyl-1-phenylbut-3-enylamine (14).
AMINYL RADICAL CYCLIZATION BY MEANS OF ANODIC OXIDATION. STEREOSELECTIVE SYNTHESIS OF cis-1-METHYL-2,5-DISUBSTITUED PYRROLIDINES
Tokuda, Masao,Yamada, Yasufumi,Takagi, Toshiya,Suginome, Hiroshi,Furusaki, Akio
, p. 6085 - 6088 (2007/10/02)
Neutral aminyl radicals generated by anodic oxidation of lithium alkenylamides 2 undergo a stereoselective cyclization to give cis-1-methyl-2,5-disubstituted pyrrolidines 4.Their cis stereochemistry was confirmed by a comparison with trans-1,2-dimethyl-5-phenylpyrrolidine, the structure of which was established by X-ray crystallographic analysis of its quarternary ammonium bromide 6.
A HIGHLY REGIO- AND STEREOSELECTIVE SYNTHESIS OF INTERNAL OLEFINS VIA AN ELIMINATION OF TRIMETHYLSTANNYL GROUP
Murayama, Eigoro,Uematsu, Masahiro,Nishio, Hiroyuki,Sato, Tadashi
, p. 313 - 316 (2007/10/02)
Internal reaction of secondary alkyltin(IV) compounds having thionium ion gave internal trans olefins with high yield and regio- and stereoselectivity via 1,5- or 1,6-transfer of a hydride β to the trialkylstannyl group.
