Woodward cis-dihydroxylation

Mergott, D. J. Woodward cis-dihydroxylation. In Name Reactions for Functional Group Transformations-, Li, J. J., Corey, E. J., Eds. John Wdey Sons Hoboken, NJ, 2007, pp 327-332. (Review). 

Stereoselective cis-dihydroxylation of the more hindered side of cycloalkenes is achieved with silver(I) or copper(II) acetates and iodine in wet acetic acid (Woodward gly-colization J.B. Siddall, 1966 L. Mangoni, 1973 R. Criegee, 1979) or with thallium(III) acetate via organothallium intermediates (E. Glotter, 1976). In these reactions the intermediate dioxolenium cation is supposed to be opened hydrolytically, not by Sn2 reaction. 

Stereoselective cis-dihydroxylation. Details have been published for preparation of cither treats- or cis-1,2-cyclohexenediol by the thallium-based version of the Woodward version of the Prevost reaction (equation I).3... 

In 1958, Woodward and Bratcher reported a study on the cis-dihydroxylation of steroid intermediate 4.1 They attempted to use OSO4 as the oxidant, but obtained the undesired cis-diol diastereomer 5 with that reagent. Thus, they developed a two-step dihydroxylation sequence using I2, AgOAc, and HOAc followed by KOH. Not only did this procedure work remarkably well, it afforded the desired diol diastereomer 8 in which dihydroxylation had occurred on the more sterically hindered p face of 4. Thus, treatment of 4 with I2, AgOAc, and HOAc afforded a mixture of acetates 6 and 7. Basic hydrolysis of 6 and 7 with KOH in methanol then gave diol 8 in 71% yield after recrystallization. 

Alkenes, Arenes, and Alkanes. The catalytic cis-dihydroxylation of alkenes with iron complexes and Oxone as terminal oxidant has been reported by Che and coworkers. A wide range of electron-rich, electron-poor, aliphatic, aromatic, terminal, and o , -unsaturated alkenes were tolerated under the optimized reaction conditions. For example, methyl cinnamate could be transformed into the diol 9 on a 30 mmol scale with traces of undesired products 10 and 11 being isolated as side products (eq 98). Oxone has also been employed in the diastere-oselective dihydroxylation of alkenes in a catalytic approach to the Prevost-Woodward reaction. Up to 77% yield was obtained in the dihydroxylation of styrene however, NaI04 was found to be a superior oxidant affording the diol in 87% yield (eq 99). 

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