Sulfides 10-camphorsulfonic acid

Several chiral sulfides have been found to be suitable organocatalysts for enantiose-lective epoxidation as illustrated in Scheme 6.87A. An early example was reported by the Furukawa group using sulfides prepared from (+)-camphorsulfonic acid... 

Sulfinic esters, aromatic, by oxidation of disulfides in alcohols, 46, 64 Sulfonation of D,L-camphor to d,l-10-camphorsulfonic acid, 46,12 Sulfoxides, table of examples of preparation from sulfides with sodium metaperiodate, 46,79 Sulfur dioxide, reaction with styrene phosphorus pentachloride to give styrylphosphonic dichloride, 46,... 

Macrolides. Reaction of a-alkenyl cyclic sulfide (1) with dichloroketene is accompanied by a [3.3] sigmatropic rearrangement lo give the 10-membered thiolactone (2) (c/. 9, 153-154). After dechlorination and deprotection, reaction with camphorsulfonic acid (CSA) effects an S-to-O acyl transfer to give the mercapto lactone (3). 

Sulfur ylides, derived from benzyl bromides and an optically active alkyl sulfide, undergo base-promoted reactions with aryl aldehydes to produce optically active 1,2-diaryl epoxides. The reaction is illustrated by equation (17) and produces epoxides with optical purities in the range of 28-47% ee. The bicyclic sulfide shown in equation (17) was derived from (-i-)-camphorsulfonic acid and produces the () j )-enantiomer of the epoxide in excess. 

Oxaziridines. Davis has developed the use of chiral 2-sulfonyloxaziridines derived from camphorsulfonic acid as chiral auxiliaries in the asymmetric oxidation reactions. Although other oxaziridines may be preferable, the camphor-derived oxaziridines can be used for the oxidation of sulfides and disulfides to sulfoxides and thiosulfinates as well as for the epoxidation of alkenes. On the other hand, the camphoryloxaziridines are the preferred reagents for hydroxylation of lithium enolates of esters, amides, and ketones, as utilized in the synthesis of kjellmanianone (eq 17). ... 

Fumkawa and coworkers realized the first enantioselective substoichiometric epoxidation reaction of aldehydes via the sulfide alkylation/deprotonation route, based on their one-pot procedure for the synthesis of oxiranes using sulfides directly rather than the preformed sulfonium salts [6]. In the presence of 50mol% sulfide 1, which was prepared in three steps starting from (-l-)-camphorsulfonic acid, a 50% yield and 47% ee were obtained in the reaction of benzaldehyde with benzyl bromide under solid-liquid two-phase conditions (solid KOH/CH3CN). A catalyst turnover (TON = 2.3) was also observed when 10mol% catalyst was used in the reaction of 4-chlorobenzaldehyde (Scheme 20.3). The 0-methylated derivative of sulfide 1 gave the trows epoxides with an opposite configuration. 

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