Chiral sulfonic acid

Buffer additives Urea, surfactants, complexing agents, organic solvents Buffer additives Urea, surfactants, inorganic salts, organic solvents, sulfonic acids, chiral cyclodextrins, amines... 

Alkyl halides or alkyl sulfates, treated with the salts of sulfinic acids, give sulfones. A palladium catalyzed reaction with a chiral complexing agent led to sulfones with modest asymmetric induction. Alkyl sulfinates (R SO—OR) may be side products. Sulfonic acids themselves can be used, if DBU (p. 1337) is... 

The use of chiral auxilliaries in the Staudinger reaction has been explored extensively. Chiral imines derived from (15)-(-t-)-camphor 10-sulfonic acid <96TA2733>,... 

However, most asymmetric 1,3-dipolar cycloaddition reactions of nitrile oxides with alkenes are carried out without Lewis acids as catalysts using either chiral alkenes or chiral auxiliary compounds (with achiral alkenes). Diverse chiral alkenes are in use, such as camphor-derived chiral N-acryloylhydrazide (195), C2-symmetric l,3-diacryloyl-2,2-dimethyl-4,5-diphenylimidazolidine, chiral 3-acryloyl-2,2-dimethyl-4-phenyloxazolidine (196, 197), sugar-based ethenyl ethers (198), acrylic esters (199, 200), C-bonded vinyl-substituted sugar (201), chirally modified vinylboronic ester derived from D-( + )-mannitol (202), (l/ )-menthyl vinyl ether (203), chiral derivatives of vinylacetic acid (204), ( )-l-ethoxy-3-fluoroalkyl-3-hydroxy-4-(4-methylphenylsulfinyl)but-1 -enes (205), enantiopure Y-oxygenated-a,P-unsaturated phenyl sulfones (206), chiral (a-oxyallyl)silanes (207), and (S )-but-3-ene-1,2-diol derivatives (208). As a chiral auxiliary, diisopropyl (i ,i )-tartrate (209, 210) has been very popular. 

A series of analogous py rrolo[ 2,1 -c [ 1,4]oxazine-8-carboxy latcs 188 and 189 (Scheme 28) were obtained by cycloaddition of azomethine ylide 187 with dipolarophiles. The ylide was formed by /(-toluene sulfonic acid-mediated reaction of the benzotriazolyl chiral morpholinone 186, which can be considered as a stable crystalline azomethine ylide precursor <2001SL1841>. This procedure was applied also to morpholinone 190 that generated ylide 191 by reaction with... 

Related structures are the pseudoalterobactins A and B from Pseudoalteromonas sp. (Fig. 8,28,29) (7Si), one of the rare examples of bacterial metabolites containing an aromatic sulfonic acid (40). Chiralities of the constituents were not determined. 

The axial immobilization of chiral [Mn((S,S)-salen )j (where salen = (Si,Sj-NiN -bis(3,5-diR -salicylidene)-l,2-diRbethane-diamine R = Bu, R -R = -(CH2)4- R = Bu, R = Ph R = Pn, R R = -(CH2)4-) complexes was achieved by reaction of [Mn(salen )Cl] with sulfonic acid- or phenol-substituted crosslinked and insoluble polystyrene resins [45]. The resulting polymer-immobilized [Mn(salen )j complexes were active and enantioselective for the asymmetric epoxidation of... 

Axially chiral phosphoric acid 3 was chosen as a potential catalyst due to its unique characteristics (Fig. 2). (1) The phosphorus atom and its optically active ligand form a seven-membered ring which prevents free rotation around the P-0 bond and therefore fixes the conformation of Brpnsted acid 3. This structural feature cannot be found in analogous carboxylic or sulfonic acids. (2) Phosphate 3 with the appropriate acid ity should activate potential substrates via protonation and hence increase their electrophilicity. Subsequent attack of a nucleophile and related processes could result in the formation of enantioenriched products via steren-chemical communication between the cationic protonated substrate and the chiral phosphate anion. (3) Since the phosphoryl oxygen atom of Brpnsted acid 3 provides an additional Lewis basic site, chiral BINOL phosphate 3 might act as bifunctional catalyst. 

Sulfonylhydroxylamines and hydroxylamine O-sulfonic acid have found wide apph-cation in synthesis of amines from achiral or chiral organoboranes and boronate esters and the hydroboration-amination methodology is successfully used for direct amination of alkenes. 0-Sulfonyloximes were also found to be good reagents for synthesis of amines from organomagnesium, -copper and -zinc reagents. 

A well-defined chiral pocket produced by the binaphthyl skeleton and the appended bulky 3,3 substituents, (iii) A ring structure attached to the phosphoric acid moiety to prevent free rotation at the a-position of the phosphorus center. This feature is not found in other Bronsted acids such as carboxylic and sulfonic acids (Figure 5.2). 

Formally, the synthetic route outlined in Scheme 6 constitutes the preparation of a new ring system from another. Nucleophilic attack of amine on the sulfonate ester, a particularly good leaving group, leads to monocyclic compound 67. Conversion of the sulfonic acid moiety into a sulfonyl chloride by POCI3 then yields the sulfonyl chloride siVu, which then undergoes nucleophilic attack by the pendant amine resulting in the chiral sultam 68. 

Derivatization of chiral arylalkylamines and NMR measurement of the diastereomeric ratios can be conveniently performed using d-camphor-10-sulfonic acid, having the (l/ ,4/ ) configuration49. 

Introducing the Tau residue into a peptide according to the first approach demands protection of the amino group, usually in the form of a Z-derivative and turning the sulfonic acid into sulfonyl chloride. Synthesis of (j-su Ifonamidopeptides via an iterative process, both in solution and in the solid phase, has been described.11201 Chiral methylene sulfinamide peptides can be synthesized both in solution and in the solid phase using the sulfonyl chlorides derived from enantiomerically pure 2-substituted taurines under mild coupling conditions (DMAP catalysis and excess methyl trimethylsilyl dimethylketene acetal as a proton trap).11261... 

Chiral halohydrins epoxides.1 The esters (2) of the chiral alcohol 1 derived from camphor-10-sulfonic acid, are converted to a-chloro esters (3) by O-silylation and reaction with NCS with high diastereoselectivity. Reduction of 3 with Ca(BH4)2 results in the recovered auxiliary and the chlorohydrin 4 with clean retention. Cyclization of 4 to the terminal epoxide 5 proceeds with clean inversion. 

Camphor- 10-sulfonic acid, 62 (S)-2-(l-Hydroxy-1-methylethyl)-pyrrolidine, 146 a-Methylbenzylamine, 185 Quina alkaloids, 264 Cycloaddition reactions 2-Oxazolidones, chiral, 225 Cyclopropanation Diiodomethane-Diethylzinc, 276 Simmons-Smith reagent, 275 Deprotonation Lithium amides, chiral, 159... 

Other methods to form carboxylic acids Cyanotrimethylsilane, 87 a-Substituted carboxylic acids (see also Amino acids, Halo carbonyl compounds, Hydroxy acids) Camphor-10-sulfonic acid, 62 Chiral compounds Alcohols... 

Camphor-10-sulfonic acid, 62, 64 Chiral Auxiliaries, Chiral Catalysts, and Chiral Ligands... 

Chiral acids, such as (+)-tartaric acid, (—)-malic acid, (—)-mandelic acid, and (+)-camphor-10-sulfonic acid, are used for the resolution of a racemic base. 

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