Alcohols 10-camphorsulfonyl chloride

The Aggarwal group has used chiral sulfide 7, derived from camphorsulfonyl chloride, in asymmetric epoxidation [4]. Firstly, they prefonned the salt 8 from either the bromide or the alcohol, and then formed the ylide in the presence of a range of carbonyl compounds. This process proved effective for the synthesis of aryl-aryl, aryl-heteroaryl, aryl-alkyl, and aryl-vinyl epoxides (Table 1.2, Entries 1-5). 

After finding the right combination for the diamine linkers, Yus et al. tried to determine whether it was compulsory to use two isoborneol-10-sulfonamide moieties. In this context, these authors have prepared the ligand depicted in Scheme 4.24 by reaction of the best amine linker, trani-cyclohexane-1,2-diamine, with camphorsulfonyl chloride and then with methanesulfonyl chloride, followed by reduction with AlH(i-Bu)2 and then hydrolysis.When this new ligand was involved in the enantioselective addition of ZnEt2 to acetophenone, the expected tertiary alcohol was obtained in excellent yield and enantioselectivity of 96% ee, as shown in Scheme 4.24. According to this result, the authors concluded that the second isoborneol unit seemed not to be necessary to obtain a high enantioselectivity. 

D,L-10-Camphorsulfonyl chloride may be oxidized to ketopinic acid (p. 55). The optically active forms of the sulfonyl chloride are useful for resolving alcohols and amines into optical antipodes. 

Camphorsulfonyl chloride has been widely used as a chiral deriva-tizing agent for the assay of enantiomeric purity of alcohols and amines by NMR techniques. A typical procedure for the preparation of the sulfonate ester or sulfonamide involves mixing a solution of the alcohol or amine in CH2CI2 with camphorsulfonyl chloride in the presence of an amine base (EtsN, py, or DMAP). This reagent has been particularly valuable for determining the enantiomeric purity of secondary alcohols (1, 2) and p-hydroxy esters (3). ... 

Camphorsulfonyl chloride has been used as a chiral starting material for the synthesis of a number of products such as ketopinic acid (eq 9), which has been used to resolve alcohols and hemiacetals, ... 

The same year, Gerlach described a synthesis of optically active 1 from (/ )- ,3-butanediol (7) (Scheme 1.2). The diastereomeric esters produced from (-) camphorsulfonyl chloride and racemic 1,3-butanediol were fractionally recrystallized and then hydrolized to afford enantiomerically pure 7. Tosylation of the primary alcohol, displacement with sodium iodide, and conversion to the phosphonium salt 8 proceeded in 58% yield. Methyl-8-oxo-octanoate (10), the ozonolysis product of the enol ether of cyclooctanone (9), was subjected to Wittig condensation with the dilithio anion of 8 to give 11 as a mixture of olefin isomers in 32% yield. The ratio, initially 68 32 (E-.Z), was easily enriched further to 83 17 (E Z) by photolysis in the presence of diphenyl disulfide. The synthesis was then completed by hydrolysis of the ester to the seco acid, conversion to the 2-thiopyridyl ester, and silver-mediated ring closure to afford 1 (70%). Gerlach s synthesis, while producing the optically active natural product, still did not address the problem posed by the olefin geometry. 

The pinacol rearrangement of sulfonate esters derived from a-hydroxy acetals proceeds by way of intermediate oxonium species, which upon hydrolysis are transformed to the corresponding esters. Sulfonate 24, prepared in optically pure form by classical resolution of the diastereomer-ic mixture obtained from reaction of (-)-camphorsulfonyl chloride with the racemic naph-thenyl alcohol, undergoes thermal [1,2] rearrangement to yield the corresponding ester29. 

Camphorsulfonyl chlorides 45 readily form amides by reaction with amines. On reduction of the carbonyl group, alcohols, e.g., 46 and 47, are obtained which are extremely useful auxiliaries for many purposes. Thus, esters are formed with carboxylic acids which may then undergo enolate reactions (SectionsD.1.1.1.3.2., D.l.5.2.1., D.3. and D.7.1.) or act as dienophiles and dipolar-ophiles (Sections D.l.6.1.1.1.2.2.1. and D.l.6.1.2.1.). Enol ethers of these auxiliaries give [2 + 2] cycloadditions with dichloroketene (Section D.l.6.1.3.), while carbamate derivatives have been used in acyliminium reactions (Section D.l.4.5.). Generally, steric hindrance in the sulfonamide group improves the stereoselectivity of the reactions and, therefore, the amides with diisopropylamine and dicyclohexylamine are used as auxiliaries both enantiomers of the dicyclohexyl derivative are commercially available. 

Camphorsulfonyl chloride has been widely used as a chiral deriva-tizing agent for the assay of enantiomeric purity of alcohols and amines by NMR techniques. A typical procedure for the... 

Camphorsulfonyl chloride can be used as a resolving reagent for chiral amines, alcohols, and binaphthols. Derivatives of camphor-sulfonates and camphorsulfonamides are generally crystalline compounds and frequently form crystals suitable for X-ray analysis. For example, racemic 3,3,3-trifluoroalanine derivative 22 was resolved into optically pure sulfonamides 23a and 23b by deriva-tization with (15)-camphorsulfonyl chloride followed by HPLC separation (eq 11). Upon recrystallization from ethyl acetate-hexane (1 5), isomer 23a forms white needles and X-ray analysis established its configuration as R,S). 

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