Payne reagents

A monoallyl substrate such as phenyl allyl ether can be epoxidised with Paynes reagent or peracids in good yield (Fig. 6). 

Fig. 6. Epoxidation of phenyl allyl ether with Paynes reagent...

In a variation on this theme MgioAl2(OH)24C03 has been shown to catalyze the oxidation of a variety of olefins-linear and cyclic-and unsaturated alcohols and ketones with H2O2 in the presence of benzonitrile [60]. The reaction involves in situ formation of the Payne reagent [61], PhC(OOH)=NH, by base-catalyzed reaction of H2O2 with benzonitrile (Eq. 5). Reaction with the olefin then affords the epoxide and one equivalent of benzamide (Eq. 6). 

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... 

The aza-Payne rearrangement of activated /V-Ts- , -disubsfiluted-aziridinemeth-anols, induced by NaOH in the mixed solvent r-BuOH-H20-THF (4 5 1) or NaH in the mixed solvent THF-HMPA (10 1), and also some iV-Boc-a,a-disubstituted-aziridinemethanols with the latter reagent-solvent combination, provides the corresponding epoxides in up to 99% yield.20... 

In contrast, epoxidation with Payne s reagent results only in 4. The epoxide 3 has been used to prepare methyl 6a-fluoroshikimate (5) by treatment with HF in pyridine and removal of the acetonide group. 

Epoxidation. This reagent is more reactive than the similar reagents of Payne derived from aceto- and benzonitrile (1, 469-470). Its reactivity is comparable to that of m-chloroperbenzoic acid. It epoxidizes a,(3-cnoncs it does not effect Baeyer-Villiger oxidation or oxidation of nitrile groups. 

A new example of the aza-Payne rearrangement has been used to prepare a-hydroxyaziridines <2005OL3267>. The epoxy imine 673 is prepared by a sequential epoxidation and imination. Reaction of 673 with a series of alkyllithium reagents initially adds to the imine which then does an aza-Payne rearrangement to form the hydroxy-aziridine 674 (Scheme 165). While the method generally suffers from poor yields, the one-step nature of the transformation lends greatly to its appeal. 

The Payne rearrangement is cited on p. 79, Eq. 114, Ref. 739. Fully substituted fluorooxiranes have been prepared from an a-haloketone with a Grignard reagent followed by hydrogen bromide elimination (Eq. 59). ... 

Nucleophilic Opening at C(l). The latent reactivity at C(l) can be activated via the Payne rearrangemenf by treatment of 2,3-epoxy alcohol A with aqueous NaOH in the presence of a cosolvent. This results in equilibration of A with the isomeric 1,2-epoxy 3-ol B. Even if epoxide A is preferred at equilibrium, C(l) in isomer B is steri-cally less hindered and hence should react faster with the nucleophile in an 8 2 manner. Once B is formed, it will react selectively and irreversibly with the nucleophile to furnish product C. The success of epoxide opening (B C) by nucleophiles depends on whether the reagent is compatible with the alkaline aqueous medium required for the Payne reaiTangement. 

Scheme 8.9. Reagent-controlled synthesis of L-allose ((+)-AE = Sharpless AE using L-(+)-DIPT (-)-AE = Sharpless AE using d-(-)-DIPT). (a) A Sharpless AE followed by Payne rearrangement and oxidation, (b) Stereodifferentiation of the C-4 and C-5 stereocenters, (c) Chain extension followed by reagent-controlled oxidation of the olefin, (d) Completion of the synthesis.

Nitroxides. Payne s reagent is the most satisfactory oxidant for conversion of substituted piperidines to their nitroxides in a nonpolar solvent. The reaction is catalyzed by sodium tungstate. Yields are equally high with m-chloro-... 

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