Regioselective sulfonation

H. G. Bazin, T. Polat, and R. J. Linhardt, Synthesis of sucrose-based surfactants through regioselective sulfonation of acylsucrose and the nucleophilic opening of a sucrose cyclic sulfate,... 

Murakami, T, K Harata and S Morimoto (1987). Regioselective sulfonation of a secondary hydroxyl group of cyclodextrins. Tetrahedron Letters, 28(3), 321—324. Zhanga P and AW Colemana (1993). Synthetic route for selective modification of the secondary hydroxyl face of cyclodextrins. Supramolecular Chemistry, 2(4), 255-263. 

Whereas the previous arene electrophilic substitutions take place at ortho position of pyridine coordinating group, the sulfonation with arylsulfonyl chloride of phenylpyridines but in the presence of a ruthenium(II) catalyst [RuCl2(p-cymene)]2 surprisingly led Frost et al. to observe for the first time an unexpected regioselective sulfonation at weto-position of the directing 2-pyridyl group [(Eq. 49)] [111]. 

Various terminal allylic compounds are converted into l-alkenes at room temperature[362]. Regioselective hydrogenolysis with formate is used for the formation of an exo-methylene group from cyclic allylic compounds by the formal anti thermodynamic isomerization of internal double bonds to the exocyclic position[380]. Selective conversion of myrtenyl formate (579) into /9-pinene is an example. The allylic sulfone 580 and the allylic nitro compound... 

Desulfonylation of equally substituted allylic sulfones with NaBH4 and LiBHEt3 usually yields a mixture of regioisomeric alkenes[406,407]. However, the regioselective attack of the less substituted side of the unsymme-trically substituted allylic system with LiEtjBH has been utilized for the removal of the allylic sulfone group in synthesis of the polyprenoid 658[408],... 

Also, the observed highly regioselective course in the SnFI substitutions in 2-R-3-nitro-l, 8-naphthyridines (R = FI, OFI, Cl, NFI2, OEt) with the anion of chloromethyl phenyl sulfone was explained by MNDO quantum-chemical calculations showing that, like in the aminations, the interaction of FIOMO of the nucleophile with LUMO of the nitronaphthyridines controls the regioselectivity (91JFIC1075). 

Regioselective lithiation of the formamidine 365 followed by tosylation afforded the corresponding 7-sulfone 367 which upon reaction with... 

Stable enolates such as diethyl malonate anions react with allyl sulfones (or acetates) in the presence of nickel complexes to give a mixture of the a- and /-product83. The regioselectivity is generally poor in the nickel-catalyzed reaction, but the molybdenum-catalyzed reaction is selective for alkylation at the more substituted allylic site, thereby creating a quaternary carbon center84. 

For trisubstituted olefins, the nucleophile attacks predominantly at the less substituted end of the allyl moiety, e.g. to afford a 78 22 mixture of 13 and 14 (equation 7). Both the oxidative addition of palladium(O) and the subsequent nucleophilic attack occur with inversion of configuration to give the product of net retention7. The synthesis of the sex pheromone 15 of the Monarch butterfly has been accomplished by using bis[bis(l,2-diphenylphosphinoethane)]palladium as a catalyst as outlined in equation 87. A substitution of an allyl sulfone 16 by a stabilized carbon nucleophile, such as an alkynyl or vinyl system, proceeds regioselectively in the presence of a Lewis acid (equation 9)8. The... 

The nucleophilic vinylic substitution reaction of ( )-a-haloenyne sulfones with sodium alkoxides proceeds regioselectively to give ( )-a-alkoxyenyne sulfones. These conqioimds are versatile intermediates for the preparation of iiirans (Scheme 15, <96TL7381>). 

Phenyl vinyl sulfones reacted with cyclohexanone enamines 332 to afford adducts which, upon hydrolysis, gave 2-(2-phenylsulfonyl)alkylcyclohexanone 333a . However, in the reaction with phenyl styryl sulfone, two products 333b and 334 were obtained by the nucleophilic attack at the and a-carbon atoms . Steric effects, electrostatic interactions between the nitrogen atom of the enamine and the oxygen atoms of the sulfone group, and medium effects contribute to the regioselectivity of the reaction. ... 

The NMR and infrared spectra of the derivatized model compounds are useful In establishing the structures and the D.F. of the modified polymers. Careful assignment of all peaks in the 13C-NMR spectra for each of structures 7-13 confirms the regioselectivity of the substitution on the oxyphenyl unit and inertness of the phenyl sulfone units. The chemical shifts of the key carbons for the analysis, those of the oxyphenyl rings, are summarized in Table I. 

In the tris-pentafluorophenyl analog (TFPC), in contrast to other Co corroles, aromatic amines can substitute PPh3 to form six-coordinate trivalent bis(amine) complexes.788 Bis-chlorosulfon-ation of TFPC occurs regioselectively to give the 2,17-(pyrrole)-bis-chlorosulfonated derivative fully characterized as its triphenylphosphinecobalt(III) complex.789 The amphiphilic bis-sulfonic acid was also obtained. 

Control of the regioselectivity of VNS is important. It is governed by three major factors the structure of the nitroarene the nature of the nucleophile, and the reaction conditions, especially solvent and base. The different effect of methoxy and hydroxy groups is interesting the reaction of l-methoxy-2,4-dinitrobenzene with chloromethyl phenyl sulfone proceeds in... 

Radical-induced addition of 4-MeC6H4S02-SePh to conjugated ynenyl sulfones occurs in a trans-fashion with high regioselectivity (Equation (70)).203... 

The 1,3,2-dioxastannolanes are important in organic synthesis because they can readily be derived from dialkyltin oxide and 1,2-diols, as in carbohydrates the reaction can be carried out in toluene in a few minutes under microwave irradiation.387 The dioxastannolanes can then be subjected to regioselective reaction with an electrophile such as an acyl chloride (Equation (140)) or sulfonyl chloride, or an isocyanate. The acylation or sulfonation can be carried out with catalytic amounts of the dialkyltin oxide, including the recoverable (C6F13CH2CH2)2Sn0.388... 

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