Camphorsulfonic acid, reaction

A -sulfinyl chiral auxiliaries have been used to prepare enantiopure tetrahydro-P-carbolines and tetrahydroisoquinolines in good yields under mild reaction conditions. Both enantiomers of V-p-toluenesulfinyltryptamine 46 could be readily prepared from the commercially available Andersen reagents.Compound 46 reacted with various aliphatic aldehydes in the presence of camphorsulfonic acid at -78 °C to give the A-sulfinyl tetrahydro-P-carbolines 47 in good yields. The major diastereomers were obtained after a single crystallization. Removal of the sulfinyl auxiliaries under mildly acidic conditions produced the tetrahydro-P-carbolines 48 as single enantiomers. 

The hydroxylation reaction, whose stereochemical course is controlled by the strong inherent preference for the formation of a cis-fused 5,5 ring system, creates a molecule which would appear to be well suited for an intramolecular etherification reaction to give ring E of ginkgolide B (1). Indeed, when a solution of 11 in methylene chloride is exposed to camphorsulfonic acid (CSA), a smooth cycli-zation reaction takes place to give intermediate 10 in an overall yield of 75% from 12. The action of CSA on 11 produces a transient oxonium ion at C-12 which is intercepted intramolecularly by the proximal hydroxyl group at C 4. 

Using oxathiane 11, ( + )-(i )-2-methoxy-2-phenylpropanoic acid was obtained in 97% ee, however, the synthesis contains some inconvenient reaction steps. Thus, reduction of ( + )-10-camphorsulfonic acid (8) leads in low yield to a mixture of 10-mercaptoisoborneol (9 A) and 10-mercaptoborneol (9B) which must be separated by chromatography. The oxathiane 10 resists deprotonation with butyllithium and, therefore,, y -butyllithium had to be employed. Furthermore, after addition of methylmagnesium iodide, cleavage of the oxathiane moiety 12, with iodomethane did not proceed as well as with the simpler oxathianes 3. 

An interesting phenomenon has been observed in the high pressure Diels-Alder reactions of the l-oxa[4.4.4]propella-5,7-diene (117) with 1,4-naphthoquinone, maleic anhydride and N-phenylmaleimide, where the diene 117 undergoes a rearrangement to the diene isomer 118 which, although thermodynamically less favored, exhibits a greater reactivity [40]. The reactivities of the three dienophiles differed since maleic anhydride and N-phenylmaleimide reacted only in the presence of diisopropylethylamine (DIEA) and camphorsulfonic acid (CSA), respectively (Scheme 5.15). The distribution of the adduct pairs shows that the oxygen atom does not exert a consistent oriental dominance on TT-facial selectivity. 

LP-DE also promotes and accelerates intramolecular Diels-Alder reactions of low reactive polyenones. The use of a catalytic amount of camphorsulfonic acid (CSA) further accelerates the cycloaddition and enhances the diastereo-selectivity [41]. Table 6.7 illustrates the effect of CSA on the intramolecular Diels-Alder reaction of 2-methyl-l,7,9-decatrien-3-one. 

Whereas cycHzation of the cu-keto-co -hydroxyamide 1466 in boihng toluene or xylene in the presence of camphorsulfonic acid (CSA) results in decomposition of the starting material 1466, heating of 1466 with excess TMSOTf 20 and N-methyl-morphoHne in 1,2-dichloroethane affords 46% of the desired cycHzation product 1467 [30] (Scheme 9.16). The close relationship of product 1467 to d -oxazolines suggests that reaction of carboxylic acids 11 with free (or C-substituted) ethanola-mines 1468 and HMDS 2/TCS 14 might lead analogously, via the silylated intermediates 1469, to d -oxazolines 1470 and HMDSO 7. As demonstrated in the somewhat related cyclization of 1466 to 1467, combination of TMSOTf 20 with N-... 

In 2003, these authors developed the Ti-catalysed enantioselective addition of ZnEt2 to benzaldehyde in the presence of C2-symmetric bis(camphorsulfo-namides) ligands derived from achiral 1,2- and 1,3-diamines and ( + )-camphorsulfonic acid. These authors showed that the stereochemical outcome of the reaction was highly influenced both by the structure of the... 

Phosphorus pentachloride, in conversion of D,L-10-camphorsulfonic acid to add chloride, 45,14 reaction with methyl formate to yield dichloromethyl methyl ether, 47, 47... 

Camphorsulfonic acid was purchased from Tokyo Kasei Kogyo Co., Ltd. (+)-10-Camphorsulfonic acid could be reduced to 0.1 equiv of the starting material with prolonged reaction time. The checkers used ( )-10-camphorsulfonic acid purchased from Aldrich Chemical Company, Inc. 

In a 2-1., three-necked, round-bottomed flask (Note 1) fitted with a sealed stirrer having a Teflon blade and, on the two side necks, with gas-outlet tubes connected by rubber or plastic tubing to an etficient hydrogen chloride absorption trap (Note 2), 464 g. (2 moles) of D,L-10-camphorsulfonic acid (Note 3) is mixed with 416 g. (2 moles) of phosphorus pentachloride (Note 4). The flask is immersed in ice water and, as soon as the mixture has liquefied sufficiently, the stirrer is started but must be run slowly at first because of lumps. When the vigorous reaction has subsided, the cooling bath is removed and stirring continued until the chloride is completely dissolved (Note 5). The mixture is then allowed to stand for 3 or 4 hours. It is poured Hood ) onto 500 g. of crushed ice contained in a 2-1. beaker. This mixture is immediately poured into a second beaker containing a similar quantity of crushed ice. The mixture is then poured back and forth between the two beakers until all evidence of reaction has disappeared (Note 6). The fine white product is collected on a... 

Phosphorane, (dichloromethylene) TRIPHENYL-1, 46, 33 Phosphorus pentachloride, for conversion of D,L-10-camphorsulfonic acid to acid chloride, 46,14 reaction with styrene, 46, 99 Photolysis of substituted stilbenes to phenanthrenes, 46, 91... 

In 2006, Xu and Xia et al. revealed the catalytic activity of commercially available D-camphorsulfonic acid (CS A) in the enantioselective Michael-type Friedel-Crafts addition of indoles 29 to chalcones 180 attaining moderate enantiomeric excess (75-96%, 0-37% ee) for the corresponding p-indolyl ketones 181 (Scheme 76) [95], This constitutes the first report on the stereoselectivity of o-CSA-mediated transformations. In the course of their studies, the authors discovered a synergistic effect between the ionic liquid BmimBr (l-butyl-3-methyl-l/f-imidazohum bromide) and d-CSA. For a range of indoles 29 and chalcone derivatives 180, the preformed BmimBr-CSA complex (24 mol%) gave improved asymmetric induction compared to d-CSA (5 mol%) alone, along with similar or slightly better yields of P-indolyl ketones 181 (74-96%, 13-58% ee). The authors attribute the beneficial effect of the BmimBr-D-CSA combination to the catalytic Lewis acid activation of Brpnsted acids (LBA). Notably, the direct addition of BmimBr to the reaction mixture of indole, chalcone, d-CSA in acetonitrile did not influence the catalytic efficiency. 

Compound 264 is unexpectedly stable against light, but can easily be oxidized to the sulfoxide 265 and the sulfone 266. Sulfoxide 265 can be isolated and a-activated by reaction with acetic anhydride (Scheme 4.46). a-Acetoxylated tetrahydrothio-phene 267 has 0,S-acetal-like reactivity and can be functionalized with various alcohols or thiols under acid catalysis with camphorsulfonic acid (CSA) (268). 

For sensitive amino acids prone to thermal dimerization to the related diketopiperazines, the reaction can be conducted in refluxing tetrahydrofuran solution in the presence of p-toluene- or camphorsulfonic acid as catalyst. Where possible the non acid-catalyzed thermal procedure is preferred since it generally provides cleaner products in higher yields. 

A mixture consisting of aniline ( 0.2 g) and (lS)-(+) camphorsulfonic acid (3.48 g) was dissolved in 10 ml of water and then treated with five separate portions of 0.1 g of ammonium peroxydisulfate dissolved in 1 ml water. Each successive portion was added when the solution turned from blue to green while the reaction mixture was maintained at 20°C. After the additions were completed the mixture was centrifuged and the product washed with water. The circular dichroism spectrum of the product suspensed in water indicated a molar ellipticity of about 90 x 103 deg-cm2/dmol. Transmission electron micrographs showed that the product had a nanofibrous structure with fiber diameters from 30 to 70 nm and had a length of several hundred nanometers. 

Approximately 2ml of aniline was added to 200ml of 1.0M aqueous (lS)-(+) camphorsulfonic acid solution and then treated with ammonium peroxydisulfate (1.15 g) dissolved in 10ml aqueous solution of 1.0M (lS)-(+) camphorsulfonic acid. The solution of ammonium peroxydisulfate was quickly added over several seconds to the solution of aniline and then stirred for 90 minutes. After the reaction was completed, the precipitate was collected and washed with about 400 ml of an aqueous solution of 0.1 M (lS)-(+) camphorsulfonic acid. Washing was repeated until the filtrate was colorless. 

Synthesis (Pohland, 1953 1955 1963 janssen and Karel (Janssen)1956 Sullivan et al., 1963) In the Grignard reaction of 3-dimethylamino-2-methyl-1-phenyl-propan-lone with benzylmagnesium chloride 4-dimethylamino-3-methyl-1,2-diphenyl-butan-2-ol is formed. The preferred product is the a-diastereomer(75 % a-form, 15 % p-form). The a-form crystallizes and the diastereomeric p-form remains in solution, because of its better solubility. Racemic resolution to obtain the analgetically (+) enantiomer can be achieved on the pure a-Grignard product via fractional crystallization of the salts with D-camphorsulfonic acid. Alternatively the resolution can be achieved by treating the racemic mannich product 3-dimethylamino-2-methyl-1-phenyl-propan-1-one with (-)-dibenzoyltartaric acid in acetone as solvent. 

Some heterocycles can be linked to supports as tetrahydropyranyl derivatives. Attachment of indoles, purines, or tetrazoles (Table 3.29) has been achieved by treatment of a support-bound dihydropyran with the heterocycle in the presence of catalytic amounts of pyridinium tosylate [487], camphorsulfonic acid [539], or TFA [540] in DCE at 60-80 °C for 16-24 h. Indole-derived orthoesters, such as that in Entry 7 (Table 3.29), can be prepared by heating the indole with triethyl orthoformate (160 °C, 24 h) followed by acid-catalyzed reaction of the resulting orthoester with a resin-bound diol [541,542], As illustrated by Entry 8 (Table 3.29), indoles can also be linked to the Wang resin or related supports as carbamates. Cleavage by TFA is, how-... 

Asymmetric acetoxylation of esters.3 Reaction of lead tetraacetate with the silyl enolate of the chiral ester 2 derived from camphorsulfonic acid results in a-acetoxylation with high diastereoselectivity. After crystallization 3 is obtained in 95% de. The product can be hydrolyzed to the optically active a-acetoxy carboxylic acid by K2C03 or reduced to the chiral glycol 4 by LiAlHj. 

The dione 214 upon treatment with hydrazine afforded 215, which was converted into 2,2 -bis(bromomethyl)-3,3 -biquinazoline-4,4 -dione 217 (Scheme 47) via 216. The racemic 1,2,5-triazepine ( )-53 was obtained from 217 by reaction with aqueous ammonia in THF. The enantiomerically pure (—)-53 was formed by refluxing ( )-53 with (+)-CSA (camphorsulfonic acid) <1999CC1991>. It is interesting that this work is the first nonracemic example of a C2-symmetric bis-heterocycle, which is atropisomeric by virtue of retarded rotation around an N-N bond. 

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