Sulfoxides, synthesis

A major problem with the sulfoxide synthesis using menthyl sulfmates is its failure to produce optically pure dialkyl sulfoxides. The prerequisite menthyl alkanesulfinates are oils which have resisted separation into the individual epimers. The menthyl phenyl methanesulfmates are an exception the R epimer is crystalline . One solution to this problem, at least for preparing methyl alkyl sulfoxides, was achieved using cholesteryl methanesulfmates (27) . Both epimers were crystalline and could be separated by fractional crystallization, although in poor yield. Treatment of the epimers with n-propyl, n-butyl, isobutyl, p-tolyl and benzyl magnesium halides yielded the respective methyl alkyl sulfoxides (28) in greater than 95% e.e. and in 32 to 53% yields. 

Scheme 14.14 mCPBA-mediated sulfoxidation synthesis of rabeprazole (6). 

For less reactive thiazines sodium periodate or 3-chloroperbenzoic acid are suitable reagents for sulfoxide synthesis but it is not always possible to prevent over-oxidation and the formation of the corresponding sulfone (75JCS(P1)716>. Carbonyl substituents at C-6... 

Gngnard reagents - [BROMINE COMPOUNDS] (Vol 4) - [ESTERS, ORGANIC] (Vol 9) -from benzene [BENZENE] (Vol 4) -chemiluminescence [LUMINESCENTMATERIALS - CHEMILUMINESCENCE] (Vol 15) -magnesium alkyls from [MAGNESIUM COMPOUNDS] (Vol 15) -reaction of propylene oxides [PROPYLENE OXIDE] (Vol 20) -for silanes [SILICON COMPOUNDS - SILANES] (Vol 22) -for sulfoxide synthesis [SULFOXIDES] (Vol 23)... 

Reaction of Methyl 4,6-0-Benzylidene-3-C-methyl-2-0-p-tolylsulfonyI-a-D-allo-pyranoside with Sodium Methoxide in Methyl Sulfoxide Synthesis of 6-Deoxy-3-C-methyl-3-O-methyl-D-allose (2-Hydroxy-D-cladinose), G. B. Howarth, W. A. Szarek, and J. K. N. Jones, Carbohydr. Res., 11 (1969) 257-262. 

Colobert, F., Tito, A., Khiar, N., Denni, D., Medina, M. A., Martin-Lomas, M., Ruano, J.-L. G., Soiiadie, G. Enantioselective Approach to Polyhydroxylated Compounds Using Chiral Sulfoxides Synthesis of Enantiomerically Pure myo-lnositol and Pyrrolidine Derivatives. J. Org. Chem. 1998, 63, 8918-8921. 

DENO t mixed oxide catalysts are used in power plants, waste incineration plants, hydration, aldol condensation, ROMP, and dimethyl sulfoxide synthesis. 

A platform had been created from which it was felt that the enantioselective sulfoxide synthesis could be developed into a process that would match logistical as well as quality requirements. However, it is important to stress that other variations of the titanium-catalyzed approach had been concomitantly identified but the decision was taken to focus solely on the present option. One of the most important and challenging aspects in this regard was to demonstrate how the oxidation step could be fitted into the existing manufacture of the prochiral sulfide (pyrmetazole) and, if not, what changes or modifications would be needed. This... 

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