VEDEJS Hydroxylation

Vedejs hydroxylation of 2-azetidinone.x Some 3-alkyl-3-hydroxyazetidine-2-ones are known to have interesting biochemical properties, but have not been readily available. They are now available by alkylation of a 3-hydroxyazetidine-2-one derivative (3), which can be prepared by hydroxylation of (N-t-butyldimethylsilyl)azeti-... 

Euolate hydroxylation (5, 269-270 8, 207-208). Vedejs hydroxylation was used twice in a biomimetic synthesis of the sesquiterpene phytuberin (1) from O -cyperone (2). In the first step, a hydroxyl group was introducechat C2 to give 3. At... 

VAN LEUSEN Reagent 397 VEDEJS Hydroxylation 398 Venketaraman 14 Verisy 251 VHIiger 13 Vnhe 399... 

Angular hydroxylation.1 Vedejs hydroxylation of 1 affords 2 (62% yield), which is a model for the antibiotic bicyclomycin (3), obtained from S. sapporonensis. 

E. Vedejs (1978) developed a general method for the sterically controlled electrophilic or-hydroxylation of enolates. This uses a bulky molybdenum(VI) peroxide complex, MoO(02)2(HMPTA)(Py), which is rather stable and can be stored below 0 °C. If this peroxide is added to the enolate in THF solution (base e.g. LDA) at low temperatures, oneO—O bond is broken, and a molybdyl ester is formed. Excess peroxide is quenched with sodium sulfite after the reaction has occurred, and the molybdyl ester is cleaved to give the a-hydroxy car-... 

Oxygenation of a silane. In the course of an anthracyclinone synthesis, Vedejs and Pribish2 found that a benzylic trimethylsilane can be converted into a hydroxyl group by reaction with TASF in the presence of oxygen and trimethyl phosphite (2 — 3,95% yield). The conversion is considered to involve formation of a benzylic... 

Next to TBHP also ferf-pentyl hydroperoxide, cumyl hydroperoxide and cyclohexyl hydroperoxide could be employed as oxidant and 2-hydroxycyclobutanone and 2-hydro xycyclododecanone were prepared by this method as well. In 1985, Vedejs and Larsen reported on a preparative method for the a-hydroxylation of camphor and a variety of other ketones utilizing overstoichiometric amounts of oxodiperoxomolybdenum(pyridine)(hexamethylphosphoric triamide) as source of oxygen (equation 67). Yields of products ranged from 34-81% and in some cases also the a-diketone is formed as by-product (0-26%). 

Stereoselective a-hydroxylation of p-trifluoromethyl esters Hydroxylation of the ester 1 with the Vedejs reagent results in predominate formation of the (2S,3S)-isomer. NaBH4 reduction of the ketone 3 shows opposite stereoselectivity. Since the steric bulk of CF3 is similar to that of CH3, electronic factors may be important. 

Enolate hydroxy lotion. a-Hydroxylation of the ketone 1 is best effected by reaction of the enolate with dibenzoyl peroxide. In this case Vedejs oxidation fails, and m-chlo-... 

Enolate hydroxylation cf. 11, 108).- Enolates of ketones or esters are oxidized by this oxaziridine to a-hydroxy carbonyl compounds. Yields are highly dependent on the base they are highest with potassium hexamcihyldisilazide. Yields are generally higher than those obtained with the Vedejs reagent (MoOPH, 8, 207). 

In a comparative study the authors demonstrated that aminium salt oxidation nicely complements the regioselectivity of other a-hydroxylation methods [173-180], which do not occur via electron transfer. Thus, using the Vedejs reagent [178] two positional isomeric products 83 and 84 were obtained from 82, whereas aminium salt oxidation leads to only one product. 

Vedejs and Larsen43 describe the preparation of MoOPH and the hydroxylation of the lithium enolate of camphor 265 to give a good yield of a 5 1 ratio of endotexo alcohols 266 while Mori-arty44 gives an example of a method we have not discussed, the hydroxylation of potassium enolates with o-iodosobenzoic acid. 

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