Diols Payne rearrangement

Sharpless and Masumune have applied the AE reaction on chiral allylic alcohols to prepare all 8 of the L-hexoses. ° AE reaction on allylic alcohol 52 provides the epoxy alcohol 53 in 92% yield and in >95% ee. Base catalyze Payne rearrangement followed by ring opening with phenyl thiolate provides diol 54. Protection of the diol is followed by oxidation of the sulfide to the sulfoxide via m-CPBA, Pummerer rearrangement to give the gm-acetoxy sulfide intermediate and finally reduction using Dibal to yield the desired aldehyde 56. Homer-Emmons olefination followed by reduction sets up the second substrate for the AE reaction. The AE reaction on optically active 57 is reagent... 

A careful analysis of this problem led to the identification of an exceedingly simple solution (see Scheme 10). The Masamune-Sharpless solution to the threo 2,3-diol problem actually takes advantage of the ready availability of the erythro 2,3-diol diastereoisomer. As we have seen in Scheme 9, erythro 2,3-diols such as 20 can be conveniently assembled from trans allylic alcohols via sequential SAE and Payne rearrangement/epoxide opening reac-... 

R,8S)-(+)-Disparlure (12) is the female sex pheromone of the gypsy moth (Lymantria dispar). Advent of Sharpless asymmetric dihydroxylation (AD) allowed several new syntheses of 12 possible. Sharpless synthesized 12 as shown in Scheme 17 [27]. Scheme 18 summarizes Ko s synthesis of 12 employing AD-mix-a [28]. He extended the carbon chain of A by Payne rearrangement followed by alkylation of an alkynide anion with the resulting epoxide to give B. Keinan developed another AD-based synthesis of 12 as shown in Scheme 19 [29]. Mit-sunobu inversion of A to give B was the key step, and the diol C could be purified by recrystallization. 

Thus far, we have discussed nucleophilic ring opening in 2,3-epoxy-l-ol taking place at the C-2 and C-3 positions (see compound 58 in Scheme 4-19). However, in the presence of a base, nucleophilic ring opening can take place at C-l via Payne rearrangement to produce 2,3-diol.36 For example, compound 1,2-... 

Payne rearrangement. The Payne rearrangement2 of a primary cts-2,3-epoxy alcohol to a secondary 1,2-epoxy alcohol usually requires a basic aqueous medium, but it can be effected with BuLi in THF, particularly when catalyzed by lithium salts. As a consequence, the rearrangement becomes a useful extension of the Sharpless epoxidation, with both epoxides available for nucleophilic substitutions. Thus the more reactive rearranged epoxide can be trapped in situ by various organometallic nucleophiles. Cuprates of the type RCu(CN)Li are particularly effective for this purpose, and provide syn-diols (3).3... 

Cyclization of halohydrins 0-16 Cyclization of 1,2-diols 0-18 Payne rearrangement of 2,3-epoxy alcohols... 

Under Payne rearrangement conditions, sodium /-butylthiolate provides 1 -/-butylthio-2,3-diols with very high regioselectivity. The selectivity is affected, however, by many factors including reaction temperature, base concentration, and the rate of addition of the thiol. These sulfides can then be converted to the l,2-epoxy-3-alcohols, which in turn react with a wide variety of nucleophiles specifically at the 1-position (Scheme 9.6). This methodology circumvents the problems associated with the instability of many nucleophiles under Payne conditions.85... 

The same group also disclosed the synthesis of epz-7-deoxypaneratistatin via an aza-Payne rearrangement (254) (Scheme 7). Analogues of narciclasine (68), pan-crastistatin, and 7-deoxypancratistatin have been synthesized using modifications of the reported procedures as well as new methodologies (e.g. addition of indoles to oxiranes and aziridines derived from cyclohexadiene diols) (255-258). 

The diol 5 was obtained from 2,3-epoxy-3-methyl-l-butanol (4) under Payne rearrangement conditions in the presence of sodium isopropyl mercaptide. The epoxide 4, in turn, was obtained from the Sharpless epoxidation of the alkene 3. The diol 5 served as a precursor for the synthesis of 2,2,5-trimethylchroman-3-ol. 

Morimoto employed Hoye s strategy of promoting cascade cyclization reactions through a base-mediated Payne rearrangement in the total synthesis of intricatetraol (181 Scheme 4.40) [75]. Diepoxide 182 reacts with LiOH to initiate a Payne rearrangement that results in an exo-cycliza-tion. The resulting epoxide opens to form the diol in 183 in the same transformation. Fnnctional gronp interconversions and dimerization provided the natnral product. 

Protection of Alcohols. The inherent stability of the MPM ether, coupled with a large repertoire of methods for its removal under mild conditions that do not normally effect other functional groups, makes it a particularly effective derivative for the protection of alcohols. The most common method for its introduction is by the Williamson ether synthesis. A number of bases can be used to generate the alkoxide, but Sodium Hydride in DMF (eq 1) or THF (eq 2) is the most common. Other bases such as n-Butyllithium, Potassium Methylsulfinyl-methylide (dimsylpotassium) (eq 3), and Sodium Hydroxide under phase-transfer conditions are also used. From these results, it is clear that protection can be achieved without interference from Payne rearrangement, and considerable selectivity can be obtained. In the ribose case, selectivity is probably achieved because of the increased acidity of the 2 -hydroxy group. The additive Tetra-n-butylammonium Iodide is used for in situ preparation of the highly reactive p-methoxybenzyl iodide, thus improving the protection of very hindered alcohols. Selective monoprotection of diols is readily occasioned with 0-stannylene acetals. ... 

The syntheas of eiy/Aro-diols by Sharpless a mmetric difaydroxylation of /-but dimetl silyl-protected allylic alcohols, followed by cyclic sul te formation and fluoride induced Payne-like rearrangement, is illustrated in Scheme 1. ... 

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