Olefins hydroxyamination

More successful asymmetric reductions have been based on amine (particularly alkaloid) complexes of bis(dimethylglyoximato) cobalt(II), also known as cobaloxime(II) and represented Co(dmg)2 (compound VII). Cobaloxime-chiral amine complexes have been used to catalyze the hydrogenation of both olefinic and ketonic substrates (Fig. 24). It has been determined that hydroxyamine modifiers, for example, alkaloids such as quinine, quinidine, and cinchonidine, are most effective. The highest optical purity obtained thus far has been 71%, observed for reduction of benzil in benzene solution at 10° using quinine as the... 

An interesting offshoot of the work on osmium-catalyzed dihydroxylations is vicinal hydroxyamination [24]. Here, imido analogs of OSO4 react with olefins to produce /5-aminoalcohols by a cw-addition process. The oxyamination reaction can be made catalytic in OSO4 by employing chloramine salts of arylsulfonamides (ArS02NClNa) or carbamates. 

However, the hydroxyamination of unsymmetrical olefins shows poor regioselectivi-ty (eq (79)) [260],... 

The synthesis of (-)-A -acetyl-O-methylacosamine, " an amino sugar, is an interesting application of the process of cis-hydroxyamination catalyzed by palladium complexes of olefins developed by Trost and Sudhakar. Enantiomerically pure aldehyde 263 was first transformed to vinyl epoxide 264. The latter reacted smoothly with p-toluene sulfonyliso-cyanate in the presence of 1-3 mol% of palladium and 6-18 mol% of tiiisopropyl phosphite in THF at room temperature. As thermal reaction favored 0-aIkylation, these conditions led exclusively to A-p-toluenesulfonyl-2-oxazolidone 265 as shown in Scheme 60. 

The novel concept of elaboration of unactivated olefins by nucleophiles has been reported. Nucleophilic attack is initiated by reaction of the olefin with dimethyl(tnethylthio)sulphonium fluoroborate (4) and, in conjunction with nitrogen nucleophiles, a high degree of regiocontrol is observed in an azasul-phenylation reaction (Scheme 7), the products of which not only permit an overall olefin amination, but also an oxazoline synthesis, a m-hydroxyamination, and an aziridine synthesis. The analogous selenium reagent, dimethyl(phenyl-seleno)sulphonium fluoroborate, p-phenylselenates a variety of anilines in moderate yield. ... 

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