Synthesis, structure, and interconversion of chiral rhenium oxygen- and sulfur-bound sulfoxide complexes of formula [(η5-C5H5)Re(NO)(PPh3)(OS(Me)R)]+ X−; diastereoselective oxidations of coordinated methyl alkyl sulfides †

Abstract

Reactions of the chiral chlorobenzene complex [(η 5 -C 5 H 5 )Re(NO)(PPh 3 )(ClC 6 H 5 )] ϩ BF 4Ϫ (1 ϩ BF 4 Ϫ ) and alkyl methyl sulfoxides O᎐ ᎐ S(Me)R (R = a, Me; b, Et; c, i-Pr or d, t-Bu), at Ϫ15 ЊC gave the oxygen-bound sulfoxide complexesϪ ; 96-20%). The triflate salts 2c,2d ϩ TfO Ϫ and 3b,3c ϩ TfO Ϫ are analogously prepared from (η 5 -C 5 H 5 )Re(NO)(PPh 3 )(OTf). Complexes 2b-2d ϩ X Ϫ and 3b-3d ϩ X Ϫ can exist as two Re, S configurational diastereomers. Stereochemistry is assigned from reactions of (S)-or (R)-1 ϩ BF 4Ϫ with enantiomerically enriched sulfoxides (R)-b-d, and a crystal structure of (S Re R S ,R Re S S )-2d ϩ TfO Ϫ ؒ0.5CH 2 Cl 2 . Relative diastereomer stabilities, and the basis for the divergent kinetic and thermodynamic oxygen/sulfur binding selectivities, are analysed. The alkyl methyl sulfide complexes [(η 5 -C 5 H 5 )Re(NO)(PPh 3 )(S(Me)R)] ϩ X Ϫ and dimethyldioxirane react (acetone, Ϫ20 ЊC) to give 3a-3d ϩ X Ϫ . Diastereoselectivities (3b-3d ϩ X Ϫ ) are fair to good. However, some overoxidation to Ph 3 P᎐ ᎐ O occurs, lowering yields.

Diastereomeric Halfsandwich Rhenium Complexes Containing Hemilabile Phosphane Ligands

“…The 1 H and 13 C NMR signals of the phenyl groups attached to phosphorus are very similar for all compounds and have therefore been omitted from the lists of spectroscopic data. 31 P NMR: Bruker AMX 400, Jeol JNM-LA 300, δ values relative to 85% H 3 PO 4 . Elemental analyses: Analytical Laboratory of the Institut für Anorganische Chemie.…”

“…[27,28] The 31 P NMR spectra of 5b, 5c and 5e exhibit this feature, an example is shown in Figure 6. The NO stretching frequency was found in the typical range for cationic ether [29] or thioether [6,30,31] complexes of the general formula [CpRe(NO)(PR 3 )(L)] ϩ . All other spectroscopic data are also in agreement with a cationic structure.…”

“…Although no crystals suitable for X-ray diffraction could be grown, the ring closure can be unambiguously inferred from 31 P NMR spectroscopic data. It is known that in chelate complexes the phosphorus chemical shift depends on the ring size.…”

Ap-cymene-ruthenium(II)–DMSO complex, [(η6-C10H14)RuCl2(DMSO)]

“…The homochiral sulfoxides have received considerable attention recently owing to their prominent role as intermediates in enantioselective synthesis and their potential use as precursors (Schenk et al, 1997;Otto et al, 2001). Because of our continuing interest in the area of arene ruthenium chemistry (Singh et al, 2000), we reacted [{( 6 ±C 10 H 14 )RuCl 2 } 2 ] with 4-cyanophenyl imidazole, which contained dimethylsulfoxide as solvate.…”

Transition Metal Catalyzed Asymmetric Oxidation of Sulfides

“…%) catalyzed oxidation of sulfides (with kinetic resolution of the sulfoxides taking place as well) with 30% H 2 O 2 gave sulfoxides with low to moderate ees; however, the antiulcer sulfoxide drug (R)-Lansoprazole was obtained in 84% yield with 88% ee [176]. It is also worth mentioning the oxidation of sulfides with chiral oxaziridines activated with general Lewis acids (ZnCl 2 ) [177] and the strategies based on the oxidation of metal complexed prochiral thioethers [178,179]. …”