Benzene derivatives dihydroxylation

The formation of chiral 1,2-diols can be achieved by dihydroxylation of benzene derivatives by using appropriate enzymes or whole cell systems, in particular Pseudomonasputida (5.89). This biotransformation reaction provides cyclohexa-diene diols in essentially enantiopure form. Many of these diols are commercially available and can be converted to a variety of different enantiomericaUy enriched compounds. For example, protection of diol 90 as its acetonide and aziridination... 

Dibydroxylaminobenzene (called Dihydroxyl-amino-benzol or Phenylenedihydroxylamin in Ger), C6H4(NH.OH)2, may be considered as the parent compd of its derivs 1,4-Di(nitrosohydroxylamino)-benzene (called 1.4 Bis-nitrosohydroxylamino-benzol or "p-Dmitroso-phenylen-dihydroxylamin, in Ger),... 

In basic chemicals, nitrile hydratase and nitrilases have been most successful. Acrylamide from acrylonitrile is now a 30 000 tpy process. In a product tree starting from the addition of HCN to butadiene, nicotinamide (from 3-cyanopyridine, for animal feed), 5-cyanovaleramide (from adiponitrile, for herbicide precursor), and 4-cyanopentanoic acid (from 2-methylglutaronitrile, for l,5-dimethyl-2-piperidone solvent) have been developed. Both the enantioselective addition of HCN to aldehydes with oxynitrilase and the dihydroxylation of substituted benzenes with toluene (or naphthalene) dioxygenase, which are far superior to chemical routes, open up pathways to amino and hydroxy acids, amino alcohols, and diamines in the first case and alkaloids, prostaglandins, and carbohydrate derivatives in the second case. 

The (R)- and (5)-benzyl epoxypropyl ether have been derived from O-benzyl-L-serine [190]. Stable and easily-handled protected forms of L- and D-glyceraldehyde are obtained by the Sharpless asymmetric dihydroxylation of the benzene-1,2-dimethanol acetal (50) of acrolein ( Scheme 37). The method produces either diol (R)-51 or (5)-51 with 97% ee after recrystallization from benzene. These diols can be converted into useful C-3 chiral building blocks, for instance epoxides (R)-52 and S)-52, respectively [191]. 

Photoinduced Charge Transfer Osmylation. The reaction of osmium tetroxide with benzenoid derivatives can only be accomplished by irradiation of the mixture. This reaction had previously been shown to work (with stoichiometric osmium tetroxide) by promotion of charge transfer between the two reactants to form an ion-pair this can then collapse to form an osmate ester of benzene diol. Subsequent dihydroxylation of this intermediate appears to follow a more conventional (and stereoselective) course. The use of catalytic osmium tetroxide (in conjunction with barium perchlorate as a reoxidant) for this reaction is noteworthy, as is the formation of both inositol and conduritol derivatives in one-pot (eq SS). The photoinduced osmylation of mono-substituted arenes was possible although the yields were lower and the amount of cyclitol-type products reduced. 

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