Sulfonylation asymmetric

Asymmetric sulfonylation was also developed by Miller employing tetra-peptide catalyst 42. ° Desymmetrisation of a variety of meso-l,3-diols was examined. Asymmetric sulfonylation of rwyo-inositol derivative 35 with p-nitrobenzenesulfonyl chloride (p-NsCl) (43) as a sulfonyl donor in the presence of catalyst 42 gave monosulfonylated product 44 in high yield and enantiomeric excess (76% yield with 94% enantiomeric excess) (Scheme 22.9). 

Catalytic asymmetric sulfonylation, which is clearly more directly comparable with the above-described work involving KR and ASD of racemic secondary alcohols and 1,2-diols by acylation and phosphorylation, has received attention only very recently. Some work has been carried out by Onomura et al. into catalytic ASD of meso-1,2-diols by monosulfonylation [97] and the sulfonylative KR of racemic 2-hydroxyalkanamides [98, 99] catalyzed by chiral copper-BOX type Lewis acids, but only one report by the Miller group addresses nucleophile-catalyzed asymmetric sulfonylation. 

Hiroi K, Makino K. Asymmetric induction reactions. III. Palladium-catalyzed asymmetric sulfonylations of allylic sulfinates and acetates with chrial phosphine ligands. Chem. Pharm. Bull. 1988 36 1744-1749. 

A-Acido imines (R R"C = N —X=0) like /V-acyl (X = CR) /V-sulfonyl [X = S(R)=0]2-7 or /V-diphenylphosphinoylimines [X = P(C6H5)2]3 are masked inline derivatives of ammonia. Compared to the imines themselves these activated derivatives are better electrophiles showing less tendency to undergo undesired deprotonation rather than addition of organometal-lics1812 The apparent advantages of these compounds have been exploited for asymmetric syntheses of amines, amides, amino acids and /J-lactams1-8 I6. 

Davis and coworkers40 have developed use of diastereomerically pure 2-sulfonyl and 2-sulfamyloxaziridines for asymmetric oxidation of sulfides into sulfoxides (equation 7). The best results (using the sulfamyloxaziridines) range from 38 to 68% enantiomeric purity of the resultant sulfoxides. The structural diversity of such substituted oxaziridines, their... 

Similar reactions were undertaken by Choi et al. in the presence of a new family of A -sulfonylated p-amino alcohols possessing two stereocentres as the chiral ligands. In using the chiral sulfonylated p-amino alcohol ligand depicted in Scheme 10.41, the asymmetric addition of McsSiCN to a wide range of aldehydes afforded the corresponding cyanohydrins in both excellent yields and enantioselectivities of up to 96% ee. 

Rhodium complexes catalyze 1,2-addition of main group metal compounds to aldimines as well. Table 5 summarizes the reported methods. Electron-withdrawing substituents such as sulfonyl and acyl groups on the imino nitrogen atom are important to obtain sufficiently high reactivity. Asymmetric synthesis (diastereoselective and enantioselective) has also been accomplished. 

Davis et al.111 developed another method for reagent-controlled asymmetric oxidation of enolates to a-hydroxy carbonyl compounds using (+)-camphor-sulfonyl oxaziridine (147) as the oxidant. This method afforded synthetically useful ee (60-95%) for most carbonyl compounds such as acyclic keto esters, amides, and a-oxo ester enolates (Table 4-20). 

Two years after the discovery of the first asymmetric Br0nsted acid-catalyzed Friedel-Crafts alkylation, the You group extended this transformation to the use of indoles as heteroaromatic nucleophiles (Scheme 11). iV-Sulfonylated aldimines 28 are activated with the help of catalytic amounts of BINOL phosphate (5)-3k (10 mol%, R = 1-naphthyl) for the reaction with unprotected indoles 29 to provide 3-indolyl amines 30 in good yields (56-94%) together with excellent enantioselec-tivities (58 to >99% ee) [21], Antilla and coworkers demonstrated that A-benzoyl-protected aldimines can be employed as electrophiles for the addition of iV-benzylated indoles with similar efficiencies [22]. Both protocols tolerate several aryl imines and a variety of substituents at the indole moiety. In addition, one example of the use of an aliphatic imine (56%, 58% ee) was presented. 

Electron-deficient olefins, asymmetric epoxidation, 386-91 Electron diffraction dialkyl peroxides, 713 ozonides, 721, 723 1,2,4-trioxolanes, 740 see also Gas electron diffraction Electron-donating substituents ene reactions, 841 sulfonyl peroxides, 1005-7 Electronegative functional groups,... 

The stereoselective or stereospecific formation of these compounds and their interaction with butyllithium was studied with the help of NMR. Paquette and Freeman first applied asymmetric induction to the synthesis of four-membered rings, especially with the sulfene-enamine 2 -F 2 cycloaddition. The in situ generation of sulfene 68 by dehydrochlorination with butyllithium of the sulfonyl chloride allowed the formation of cycloadduct 69 in 88 % yield. In a variation, the sulfene may be generated by base-induced... 

In 1992, Trost and his co-workers investigated desymmetrization of cyclic w j-o-diesters with lithium sulfonyl-methylenenitronate as a nucleophile in the presence of Trost s ligand 118, where the corresponding cyclic compounds are obtained with an excellent enantioselectivity via intramolecular cyclization (Scheme 15),103,103a Asymmetric cyclopropanation and lactone annulation are achieved according to this protocol (Scheme Nitroalkanes can also be employed as carbon-centered nucleophiles in lieu of malonates (Scheme 17). ... 

---