Synthesis and reactivity of cationic iridium(I) complexes of cycloocta-1,5-diene and chiral dithioether ligands. Application as catalyst precursors in asymmetric hydrogenation †
作者:Montserrat Diéguez、Aránzazu Orejón、Anna M. Masdeu-Bultó、Raouf Echarri、Sergio Castillón、Carmen Claver、Aurora Ruiz
DOI:10.1039/a704611a
日期:——
2-dimethyl-4,5-bis(isopropylsulfanylmethyl)-1,3-dioxolane (–)-diospr and (+)-2,2-dimethyl-4,5-bis(phenylsulfanylmethyl)-1,3-dioxolane (+)-diosph were prepared from diethyl (+)-L-tartrate. An alternative synthetic method for preparing the previously described bis(methylsulfanylmethyl) dithioether (–)-diosme was devised. By co-ordinating of the dithioethers to different (cycloocta-1,5-diene)iridium(I) compounds
3a'-bispyrrolidino[2,3-b]indoline moiety found in complex indole alkaloids can be prepared, as illustrated by total syntheses of meso-chimonanthine (1) and (+)-chimonanthine (2). A rare example of high diastereoselectivity arising from the combination of a prostereogenic enolate with a chiral electrophile containing a sp(3) carbon atom is the key feature of the asymmetric synthesis of the C(2) stereoisomer.
Investigation of a Dialkylation Approach for Enantioselective Construction of Vicinal Quaternary Stereocenters
作者:Scott B. Hoyt、Larry E. Overman
DOI:10.1021/ol006494m
日期:2000.10.1
A detailed study of the dialkylation of dianions derived from dihydroisoindigo 1 with enantiopure ditriflate 2 is reported. The LHMDS-mediated process has been optimized to give C(2)-symmetric product 3 with high selectivity (C(2) selectivity 3:5 = 100:1; C(2):C(1) selectivity = 8:1). Stereoselection in the C(2) manifold is determined in both the bimolecular and intramolecular alkylation steps.
Asymmetric Epoxidation of Aldehydes Catalyzed by New C2-Symmetrical Chiral Sulfide
作者:Miyuki Ishizaki、Osamu Hoshino
DOI:10.3987/com-02-9520
日期:——
Asymmetric synthesis of chiral epoxides from various aldehydes with benzyl bromide was investigated using new C-2-symmetrical chiral sulfides, which were readily prepared from (R,R)-tartaric acid.
Novel chiral dithioethers derived from l-tartaric acid
作者:Leticia Flores-Santos、Erika Martin、Montserrat Diéguez、Anna M. Masdeu-Bultó、Carmen Claver
DOI:10.1016/s0957-4166(01)00504-3
日期:2001.11
The synthesis of a new family of systematically modified chiral dithioethers to be used as ligands is described. Phenylthioether derivative 5 and fluorine-containing dithioether ligands 6-8 and 13-15 were prepared by direct reaction of phenylthiol and o-, m- or p-fluorophenylthiol with two different ditriflate derivatives based on the L-tartaric skeleton. The chiral ditriflate 12 containing a dioxolane moiety was reacted with ethane- and propanedithiol. producing cyclic dithioethers 16 and 17, respectively, in good yields (approximate to 50%). The analogous ditriflate 4 with benzyl ether protecting groups, having a skeleton without restricted rotation, gave the thiolane 9 as the main product. (C) 2002 Elsevier Science Ltd. All rights reserved.