Chiral sulphones reactions

The preparation of (silyloxy)rhodium complexes of the type [Rh2(fi-OSiR3)2(Ti -COD)2l (R = Me, Ph), which could serve as models of rhodium complexes bound to silica, has been reported238. The synthesis of the water-soluble complex [Rh(Ti -COD)(DPPETS)]+[Cl]" (DPPETS = l,2-bis bis(m-sodiosulfonatophenyl)phosphino ethane) has been reported and its catalytic activity in two-phase hydroformylation reactions investigated. The mechanism of the homogeneous reduction of (Z)-a-acetamido and (Z)-a-benzamidocinnamic acid methyl ester and a-acetamidoacrylic acid methyl ester in an organic-water medium in the presence of catalysts derived from [Rh2(lt-Cl)2(Ti -COD)2] and chiral sulphonated phosphines has been investigated W. ... 

Miscellaneous Reactions of Phosphines.- The role of chiral phosphines as ligands in the catalysis of reactions leading to the formation of chiral products has been reviewed.1111 A procedure for the determination of the enantiomeric excess in chiral phosphines has been developed, based on 13C n.m.r. studies of the diastereoisomeric complexes formed by phosphines with the chiral pinenyl nickel bromide complex. 111 Studies of the sulphonation of triphenylphosphine and of chiral arylphosphines have been reported in attempts to prepare water soluble ligands which aid... 

Powdered KOH (113 mg) is added to the aryl aldehyde (0.6 mmol), the chloromethyl-sulphone (0.5 mmol) and A-(4-trifluoromethyIbenzyl)quininium bromide (28 mg, 0.05 mmol) in PhMe (3 ml) at room temperature and the mixture is stirred for 2 h. Aqueous HCI (l M, 3 ml) is added to quench the reaction and the mixture is extracted with AcOEt (3 x 15 ml). The extracts are washed with brine (10 ml), dried (Na2S04), and evaporated to yield the chiral oxirane. 

Solvolysis of (S)-2,6-dimethyloct-5-yl toluene-p-sulphonate gives a tetrahydro-linalool, (i )-2,6-dimethyloctan-6-ol, with about 60% retention of asymmetry. Kirmse and Arold have described several other similar reactions and suggest that a hydrophobic anchimeric interference of alkyl residues persists during the rearrangement, giving chirality to the carbonium ion. ... 

The reaction mechanism(Following fig.) involves the alcohol oxygen acting as a nucleophilic centre and substituting the chloride ion from the sulphonate. The base then removes a proton from the intermediate to give the sulphonate product. Neither of these steps affects the stereochemistry of the alcohol carbon and so the stereochemistry of chiral alcohols is retained. 

The utilization of carbohydrates for the synthesis of chiral crown ethers has been further explored, giving derivatives with the general structures (12) and (13) using 4,-6-O-benzylidene derivatives of methyl a-o-galacto-, gluco-, and manno-pyranoside in a base-catalysed reaction with diethylene glycol bis-toluene-p-sulphonate. ... 

The sulphonyloxaziridines (70) and (71) derived from (-h)- and (-)-camphor-sulphonic acid are very useful for the asymmetric synthesis of a-hydroxycarbonyl compounds, which are important and widely distributed. The reaction is performed simply by treating the prochiral enolate with the chiral oxidant, as in the example shown for preparation of either enantiomer of benzoin. 

Also of considerable encouragement were the results reported in the Darzens reaction some time ago . Carbonyl compounds when reacted with chloromethyl-p-tolyl sulphone or with chlorophenyl-acetonitrile in the presence of aqueous sodium hydroxide and chiral onium salts derived from [I] [reaction 7 and 8] yielded product epoxides with up to 2.5% enantiomeric excesses. More importantly. 

Intermediates in Reactions.— The utility of the Ramberg-Backlund rearrangement and the involvement of thiiran 1,1-dioxides in synthesis has been reviewed. Treatment of d,l- and meso-bis-oc-bromobenzyl sulphone with triphenylphosphine gave trans- and cis-stilbene, respectively, via a-sulphonyl carbanions which undergo cyclization at the remaining chiral centre to yield trans- and cis-2,3-diphenylthiiran 1,1-dioxides as intermediates (Scheme 3). Inversion occurred at each chiral centre. Thiiran... 

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