From -camphorsulfonyl

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). 

Poor (<4% de) to modest (56% de) amounts of diastereofacial selection is observed in the cycloaddition of nitrile oxides to optically active acrylates. The plan in each case, of course, was to use a chiral auxiliary which would preferentially shield one of the two ir-faces of the dipolarophile. Of the auxiliaries used, the sulfonamide esters derived from (+)-camphorsulfonyl chloride worked best, the menthyl esters derived from (-)-menthol the poorest (<4% de). As illustrated in Table 19, changes in both temperature and solvent had either no or little affect on the product ratios. Unlike Diels-Alder reactions, the addition of Lewis acids, specifically Et2AlCl, EtAlCh and TiCL, resulted in significant decreases in both the rate of cycloaddition and isolated yield, without an appreciable change in diastereomer ratio. ... 

The first convenient synthesis of compound 6 involves four steps starting from allyl bromide (Scheme 7) and gives the product in 34% overall yield <1997CC611>. This seems more suitable for large-scale synthesis than the method involving metathesis of 122 mentioned in Section 4.09.9.3. The synthesis of compound 72 mentioned in Section 4.09.9.1, which involves four steps from camphorsulfonyl chloride, is also amenable to large-scale synthesis <1999TA4183>. 

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. 

Since conjugate (Michael) addition and Diels-Alder reactions use a,p-unsat united carbonyl compounds, asymmetric versions of these reactions could use the auxiliaries that we have seen in aldol reactions in the form of 118 and 119. Diels-Alder reactions work very well with these unsaturated amides and also with amides 121 derived from Oppolzer s chiral sultam14 120, prepared simply from camphorsulfonyl chloride. 

The reaction of chiral sulfones 161, derived from (lS)-( + )-10-camphorsulfonyl chloride, with cyclopentadiene gives predominantly the endo adduct in a diastereomeric ratio of 91 9 from which one diastereomer 162 can be isolated in pure form by recrystallization (equation 115)109. 

In 2000, these workers described disulfonamide ligands derived from camphor, which could be easily prepared from chiral camphorsulfonyl chloride, and further successfully used in the enantioselective addition of ZnEt2 to... 

It was independently found by two groups that the exo-diol derived from bis(camphorsulfonyl)-substituted tra .s-cyclohexane-1,2-diamine ligand (HOCSAC) was an excellent promoter for the enantioselective addition of dialkyIzinc reagents to any type of ketones, even dialkyl ketones, in the presence of Ti(Oi-Pr)4. As shown in Scheme 4.11, excellent enantioselectivities of up to 99% ee were obtained in these conditions in combination with high yields and with a low catalyst loading of 2-10 mol%. 

D,L-Ketopinic acid has been prepared by oxidation of bornyl chloride with nitric acid at 20° or with perbenzoic acid in acetic acid from 10,10-dinitrocamphan-2-on or apocamphan-2-ol-l-carboxylic acid with alkaline permanganate and from the oxidation of 10-camphorchlorosulfoxide, obtained from 10-camphorsulfonyl chloride by the action of pyridine, with potassium permanganate. The present procedure represents a simplification of the latter and gives as high an overall yield. ... 

IO-Camphorsulfonyl chloride was prepared from 50 g of (1S)-(+)-10-camphorsulfonic acid purchased from Aldrich Chemical Company, Inc. using the procedure described by Bartlett and Knox, Org. Synth., Coll., Vol. 171973, 196. Material that was collected on the suction filter and air dried by maintaining suction for 15-20 min was of sufficient purity for the next step. The checkers obtained comparable... 

Oxidation is generally complete after addition of the oxone solution. The oxidation is monitored by TLC as follows remove approximately 0.5 mL of the toluene solution from the nonstirring solution, spot a 250-micron TLC silica gel plate, elute with methylene chloride and develop with 10% molybdophosphoric acid in ethanol and heating (camphorsulfonyl)imine R = 0.28 and (camphorylsulfonyl)oxaziridine R = 0.62. If (camphorsulfonyl)imine is detected, stirring is continued at room temperature until the reaction is complete (See Note 8). 

Camphorsulfonyl)imine has been reported as a by-product of reactions involving the camphorsulfonamide.2 5 Reychler in 1898 isolated two isomeric camphorsulfonamides,2 one of which was shown to be the (camphorsulfonyl)imine by Armstrong and Lowry in 1902.3 Vandewalle, Van der Eycken, Oppolzer and Vullioud described the preparation of (camphorsulfonyl)imine in 74% overall yield from 0.42 mol of the camphorsulfonyl chloride.6 The advantage of the procedure described here is that, by using ammonium hydroxide, the camphorsulfonyl chloride is converted to the sulfonamide in >95% yield.7 The sulfonamide is of sufficient purity that it can be used directly in the cyclization step, which, under acidic conditions is quantitative in less than 4 hr. These modifications result in production of the (camphorsulfonyl)imine in 86% overall yield from the sulfonyl chloride. 

Ligand exchange provides a route for the synthesis of chiral A3-iodanes. [(+)-10-Camphorsulfonyl]oxy-A3-iodane 8 was prepared from the reaction of 4 with (+)-10-camphorsulfonic acid in aqueous acetonitrile [22]. Concentration of a solution of [methoxy(tosyloxy)iodo]benzene and (+)-menthol in dichloro-methane under vacuum results in facile ligand exchange on iodine to give the chiral A3-iodane 9 [23]. 

Treatment of the laterally lithiated amide generated from lactam 273 with LDA with /ra r-2-phenylsulfonyl-3-phenyloxaziridine 33 afforded hydroxyl product 274 in 85% yield as a single isomer <1999JOC8627>. Use of (+)-(camphorsulfonyl)oxaziridine 202 gave similar results. The /ra t-stereoselectivity is consistent with the earlier finding that the hydroxylation stereochemistry is controlled by nonbonded steric interactions in the transition state such that the oxygen of the oxaziridine is delivered from the sterically least hindered direction. Treatment of 275 with LDA followed by (+)-(camphorsulfonyl)oxaziridine 202 afforded hydroxyl product 276 in 47% yield and 60% ee <1997T8881>. 

Synthesis of Chiral Reagents. An efficient chiral a-chloro-a-nitroso reagent derived from 10-camphorsulfonyl chloride (1, Cy2NH 2, NH2OH 3. t-BuOCl 70-78%) has been developed for the asymmetric a-amination of ketone enolates (eq 7). The resulting p-keto /V-hydroxylamine can be converted to the anti-1,2-hydro y amine under reducing conditions (NaBHt Zn, HCl, AcOH),... 

Preparative Methods crystalline, enantiomerically pure 10-diisopropyl- and 10-dicyclohexylsulfonamidoisobomeol auxiliaries are readily prepared from the appropriate enantiomer of 10-Camphorsulfonyl Chloride by successive amidation and cxtr selective reduction (eq 1). ... 

Preparative Methods both enantiomers of the a-methyl sultam may be prepared on a multigram scale in optically pure form by asymmetric hydrogenation of imine (2a) followed by simple crystallization (eq 1). The (7 )-enantiomer of the a-f-butyl sultam may also be prepared in enantiomerically pure form by asymmetric reduction of imine (2b) followed by fractional crystallization. However, multigram quantities of either enantiomer of the a-t-butyl sultam may be prepared by derivati-zation of the racemic auxiliary (obtained in 98% yield from reaction of (2b) with Sodium Borohydride in MeOH) with 10-Camphorsulfonyl Chloride, separation of the resulting diastere-omers by fractional crystallization, and acidolysis. Prochi-ral imines (2a) and (2b) are readily prepared from inexpensive Saccharine by treatment with Methyllithium (73%) and t-Butyllithium (66%), respectively. 

Resolution 3t3-Acetoxy-A. etienic add. T-Acid from a tetranitrofluorenone and an optically active hydroxylamine. i><—>Butane-2,3-diol. L.(+)-Butane-2,3-dithiol. (By crystallization Silver acetate). 10-Camphorsulfonic acid. 10-Camphorsulfonyl chloride. 4-(4-Carboxy-phenyl) semicarbazide. Complex from ethylene, platinous chloride, and (- -)-l-phenyi-2-aminopropane. Debydroataetylamine. Diisopinocampheylborane. Di-p-toluoyl-o-tartrate. d- and /-u-Phenylethylamiiie. L-Pyrrolidonecarboxylic add. a-(2,4,S,7-Tetianitro-9-fluorenyl-ideneaminooxy)-propionic acids. 

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. 

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