Camphor- 10-sulfonic acid synthesis

Complete details for synthesis of ( + )- or ( —)-l from (IS)- or (1R)-10-camphor-sulfonic acid in 77% yield are now available. In general, this oxaziridine is less active than other N-sulfonyloxaziridines, but it is the preferred reagent for hydrox-ylation of lithium enolates of esters, amides, and ketones in 30-95% ee.1... 

A large scale synthesis of a chiral tetrahydropyran derivative (five steps, 56% overall yield) from (+)-10-camphor-sulfonic acid has been described the sulfide is of value in the asymmetric synthesis of epoxides and aziridines <2006T11297>. 

SCHEME 13.6 Completion of Schmidt s synthesis of the yeast GPI anchor. CS A, camphor-sulfonic acid. 

Atropine (XXVIII) had already been prepared from ( + )-acetyltropoyl chloride and tropine (40) followed by resolution (41), using n-camphor-sulfonic acid, to obtain first the salt of dextrorotatory hyoscyamine. Recently dibenzoyltartaric acid was claimed to precipitate the salt of the ( —)-antimer first (42). Direct synthesis of hyoscyamine (XXVIII) was realized by melting S-( — )-acetyltropoyl chloride (XXXV), obtained for the first time in crystalline form, with tropine hydrochloride (XXXVI), followed by acid deacetylation of acetylhyoscyamine (XXXVII)... 

The acid used in the Fischer glycoside synthesis was originally HCl (which made the kinetic data reproducible only with difficulty, as in methanol HCl is slowly consumed to form methyl chloride). Nowadays, ion-exchange resins are used preparatively, whilst the data on 4- and 5-O-methylated glycosides were obtained with camphor sulfonic acid. 

The mechanism of the formation of these complexes was studied by the synthesis of single crystalline stoichiometric oligomeric complexes between 4,4 -bipyridine-camphor sulfonic acid [4,4 -Bpy(CSA)] and zinc camphorsulfonate Zn(CS)2. A hydration-induced bonding between PANI(DBSA)o.5 and Zn(DBS)2 was proposed. 

The synthesis of the C1-C7 fragment, which corresponds to the lactone, starts with the homoallylic alcohol 2 which was prepared from 1. The existing stereocenter and the conjugate addition method of Evans [21] allow the control of the C5 stereocenter. The homoallylic alcohol 2 was oxidatively cleaved and homologated to the trans enoate 3 by a Wittig olefination. Treatment of 3 with benzaldehyde and a catalytic amount of KHMDS provided acetal 4. The internal Michael addition of the hemiacetal intermediate proceeds with complete stereoselectivity [22]. After deprotection and oxidation, the corresponding aldehyde was treated with Amberlyst-15 and then with camphor sulfonic acid (CSA), to yield pyrane 5 as a mixture of (3- and a-anomers (1.8/1). This compound was converted to the thiophenyl acetal 6 (4 steps) as this compound can be hydrolyzed later under mild conditions (Hg +) with subsequent oxidation of the lactol to the desired lactone. Compound 6 represents the C1-C7 fragment of discodermolide (Scheme 1). 

Lu et al. [31] synthesized alumina nanotubes via the hydrothermal technique. For a typical synthesis, AKNOsjs and camphor sulfonic acid, as surfactant, were dissolved in water. An ammonia aqueous solution was added to adjust the pH value to 5.4. A Teflon-lined stainless steel autoclave heated to 160 °C was used to grow the nanotubes for 24 h. A solid precipitate was collected by centrifugation, washed with ethanol and dried in air at room temperature followed by grinding. The product of this synthesis exhibits a one-dimensional morphology with a length of 500 nm and a diameter of 50 nm, and a boehmite phase. 

The conductive salt (X ) used in the electrochemical synthesis is contained in the polypyrrole film as a dischargeable counterion. Interesting conductive salts that affect optical activity in polypyrrole are (-f) or (—)-camphor sulfonic acid (used for racemate separations), heparin, and other drugs such as monobactam. 

Polypyrrole is sensitive to moisture because this leads to leaching of the counterion and hence to a decrease in conductivity. This can be avoided by using appropriate hydrophobic or polymeric counterions (e.g. camphor sulfonic acid or poly(styrene sulfonic acid) or by incorporating hydrophilic compounds, polypyrroles obtained by synthesis in aqueous electrolytes maintain a conductivity of about 20 S cm. Polypyrroles with a perchlorate counterion are unstable under atmospheric conditions, but can be used as electrodes in rechargeable batteries. 

Auxiliary Synthesis Both the (S)- and (R)- enantiomers of the camphor-derived ACC 54 are available in seven steps from commercially available and inexpensive (S)- and (R)-camphor sulfonic acid, respectively (Scheme 7.9). The seven-step process provides an overall yield of approximately 40%. A key step in the synthesis of 54 and 55 is the direct A -amination of the corresponding oxazolidinones, 61 and 62. This transformation is effectively achieved in a straightforward manner using a modification of a procedure recently reported by Hynes et al. ° Application of this amination procedure to commercially available (R)- or (5)-4-benzyloxazolidinone ((R)-62 or (S)-62, respectively) provides phenyl alanine-derived auxiliaries (R)-55 or (S)-55 in excellent yield. 

Shingare and co-workers have presented for the first time a successful implementation of ultrasound irradiation for the rapid synthesis of a-hydroxy phosphonates (521) and a-amino phosphonates (525) under solvent-free conditions from triethyl phosphite (524), aromatic aldehydes (523) and amines (522) using camphor sulfonic acid (CSA) (Scheme 130). One-pot, three-component Kabachnik-Fields synthesis of a-aminophos-phonates (529) from carbonyl compounds (526), primary amines (527), and dibenzyl/dimethyl/diethyl substituted phosphites (528) has been carried out in high yields, using H-beta zeolite as a reusable catalyst (Scheme 131). Zhang and co-workers have developed the nickel-catalysed Arbuzov type phosphonylation to afford phenyl substituted phosphonates (532) in the reaction of aryl triflates (530) with triethyl phosphite (531), in which KBr, as an additive, promoted the Sn2 catalytic step (Scheme 132). ... 

Hoye and Richardson have published an ingeneous synthesis of the tricyclic iridoid sarracenin (170) which relied on the Paterno-Buchi cycloaddition between acetaldehyde and cyclopentadiene as the intial step (Scheme 38)79. This reaction provided a 5 1 mixture of adducts 166a and 166b. The major adduct was opened with camphor-10-sulfonic acid (CSA) in methanol and the alcohol was tosylated to give 167. Displacement with malonate 168 and decarboalkoxylation/demethylation steps gave 169. Ozonolysis, reductive workup and acid-catalyzed acetalization then furnished 170. 

Of similar nature are chiral halogenations using auxiliary groups. Typical examples are the conversion of esters to enantiomerically pure halohydrins (precursors to chiral epoxides) using camphor-10-sulfonic acid derivatives583 and the chiral synthesis of a-amino acid synthons via diastereoselective bromination of TV-acyl oxazolidone derivatives584. 

The Schmitz reaction can be unsuccessful in sterically demanding environments in such circumstances, the electrophilic aminating agent reacts faster with ammonia than with hindered ketones <1965JA2665>. Consequently, the synthesis of 2-azi-camphane 64, a compound which is unobtainable under standard conditions <1996TL6647>, was achieved by slow diaziridination of camphor imine hydrochloride 63 (rather than camphor itself) with hydroxylamine-O-sulfonic acid (HOSA)-ammonia, followed by iodine-mediated oxidation (Scheme 22) <2001S379>. 

In a similar manner, D-camphor-lO-sulfonic acid (10-CSA) has heen used in the synthesis of 2-thiazolines. In the example shown in Scheme 82, endothiopeptide 208 was converted into thiazol-5(4//)-one 209 . 

Camphor 93, a bridged monoterpene with one six- and two five-membered rings is available in both enantiomeric forms and was used by Woodward in the synthesis of vitamin B12. Sulfonation on camphor occurs on the bridgehead methyl group by a series of rearrangements described in the workbook. You will see in chapter 27 how Oppolzer s sultam 95 is used as a chiral auxiliary and in chapter 33 how oxaziridines such as 96 are used in asymmetric oxidation. Both are made from camphor-10-sulfonic acid 94. 

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