Methyl naphthyl sulfoxide

A remarkably high diastereoselective excess was obtained in the addition of the anion of (S)-(-)-methyl 1-naphthyl sulfoxide to n-alkyl phenyl ketones. The sulfoxide was prepared in optically pure form by oxidation of the complex of methyl 1-naphthyl sulfide and 13-cyclodextrin with peracetic acid followed by crystallization. Desulfurization of the adducts provided enantiomerically pure tertiary alcohols (393]. 

Stephens PJ, Aamouche A, Devlin FJ, Superchi S, Donnoli MI, Rosini C. Determination of absolute configuration using vibrational circular dichroism spectroscopy 1-(2-methyl-naphthyl) methyl sulfoxide. J Org Chem 2001 66 3671-3677. 

The method has been recently improved, in collaboration with Fiisfero (Scheme 5) (36). In fact, lithium derivative of (6>naphthyl methyl sulfoxide 21 was found to provide much better stereocontrol in the condensation with A -PMP fluoroalkyl imines 15a,b,f. The resulting A -PMP naphthyl derivatives 22 were transformed into the enantiomeric (5)-P-fluoroalaninols 20 following an identical sequence of reactions, in high overall yields and stereoselectivity. Oxidation of the hydroxymethylene group, according to the method of Sharpless (37), extended the field of application of this strategy to the synthesis of enantiopure p-fluoro alanines 23. The wide scope of the NOP reaction is demonstrated by the fact that also naphthyl sulfoxides, like 22, can be successfully submitted to the reaction. 

In redox reactions, isolated oxidative enzymes such as laccase C from Trametes and horseradish/soybean peroxidases (with mediators) have been shown to possess good catalytic activity in common ILs on syringaldizine and veratryl alcohol, respectively [35]. Recently, oxidase-peroxidase-catalyzed chemo- and stereoselective sulfoxidations of thioanisole and methyl-2-naphthyl sulfide have been successfully carried out with a system of Coprinus cinereus (CiP) peroxidase and Aspergillus niger glucose oxidase (GOD) in 10% water in [BMIM][PF6] (Scheme 2). An enantiomeric... 

Posner investigated the addition of the larger naphthyl Grignard reagent (65) to enantiomerieally pure cyelopentanone sulfoxide (66). The reaetion proeeeded with excellent enantioselectivity to provide P-naphthyl-a-methylcyclopentanone sulfoxide (67) in 42% yield and >98% de after in situ methylation of the intermediate enolate anion (Scheme 4.34) [42]. 

More recently, Murahashi has used flavin 28 to oxidize naphthyl methyl sulfide to its sulfoxide in 72% ee (Eq. (8.13)) [52]. 

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