Rearrangement to allylic alcohols

The (3-elimination of epoxides to allylic alcohols on treatment with strong base is a well studied reaction [la]. Metalated epoxides can also rearrange to allylic alcohols via (3-C-H insertion, but this is not a synthetically useful process since it is usually accompanied by competing a-C-H insertion, resulting in ketone enolates. In contrast, aziridine 277 gave allylic amine 279 on treatment with s-BuLi/(-)-spar-teine (Scheme 5.71) [97]. By analogy with what is known about reactions of epoxides with organolithiums, this presumably proceeds via the a-metalated aziridine 278 [101]. 

Regioselective rearrangement to allyl alcohols can also be attained with dialkylboryl-trifluoromethane sulfonate in the presence of tertiary amines (Eq. 152). ... 

Kd = rate of constant of rearrangement to allyl alcohol of methyl deuterated PO Kh = rate constant of rearrangement to allyl alcohol of normal undeuterated PO... 

One explanation of this effect is the propagation reaction acceleration and the deceleration of the transfer reaction. The mechanism of PO rearrangement to allyl alcohol is based on a cyclic intermediary state, in fact a weak complex alcoholate-PO ... 

Olefination of the aldehyde of 196 installed an additional carbon necessary for advancement to the natural products, giving methyl vinyl ether 197. Treatment with dimethyldioxirane at low tenperature acconplished oxidation at sulfur in the presence of the electron-rich vinyl ether, and the resulting sulfoxides (mixture of diastereomers at sulfur) underwent high-yielding Mislow-Evans rearrangement to allylic alcohol 198 under mild conditions in methanol containing trimethylphosphite and di-zso-propyl amine. The product 198 of this sequential Claisen/Mislow-Evans process was converted to either (-)-joubertinamine or (-)-mesembrine in a short series of steps. 

The utility of this method also stems from the fact that the nitro group enables C—C bond formation prior to the rearrangement. Michael addition of the anion derived from 276 to methyl vinyl ketone led to allylic nitro compound 277, which rearranged to allylic alcohol 278 in hi yield and excellent diastereoselectivity. Meanwhile, a single diastereomer of the bicyclic framework 280 was available under thermodynamic control from nitro aldehyde 279 via reversible Henry reaction, and transposition of the allylic nitro stereocenter to allylic alcohol 281 resulted from the suprafacial nature of the ensuing [2,3]-rearrangement. 

The products from reaction of cyclohexene oxide (149) with a variety of lithium alkylamides have been investigated. Major pathways are considered relevant and these involve rearrangement to allylic alcohol or ketone or direct nucleophilic substitution. With lithium monoalkylamides the reaction product is essentially partitioned between cyclohex-2-enol (150) and amino-adduct... 

Propylene oxide-based glycerol can be produced by rearrangement of propylene oxide [75-56-9] (qv) to allyl alcohol over triUthium phosphate catalyst at 200—250°C (yield 80—85%) (4), followed by any of the appropriate steps shown in Figure 1. The specific route commercially employed is peracetic acid epoxidation of allyl alcohol to glycidol followed by hydrolysis to glycerol (5). The newest international synthesis plants employ this basic scheme. 

As propylene oxide is introduced into the reactor, a portion of it is converted to allyl alcohol and propenyl alcohol via a rearrangement [5] ... 

Owing to the reversible nature of the allylic sulfenate/allylic sulfoxide interconversion, the stereochemical outcome of both processes is treated below in an integrated manner. However, before beginning the discussion of this subject it is important to point out that although the allylic sulfoxide-sulfenate rearrangement is reversible, and although the sulfenate ester is usually in low equilibrium concentration with the isomeric sulfoxide, desulfurization of the sulfenate by thiophilic interception using various nucleophiles, such as thiophenoxide or secondary amines, removes it from equilibrium, and provides a useful route to allylic alcohols (equation 11). 

The data presented demonstrate that allylic sulfoxides can provide an easy and highly stereoselective route to allylic alcohols taking advantage of the facility of the allylic sulfoxide-sulfenate [2,3]-sigmatropic rearrangement. This is of considerable synthetic utility, since a number of stereoselective and useful transformations of allylic alcohols and their derivatives have become available in recent years107-109. 

BASE-INDUCED REARRANGEMENT OF EPOXIDES TO ALLYLIC ALCOHOLS trans-Pinocarveol,... 

TT-ALLYLNICKEL HALIDES METHALLYLBENZENE, 52, 115 Rearrangement of epoxides to allylic alcohols, 53, 17 Reduction, by controlled-po-tential electrolysis, 52, 22 by lithium aluminum hydride of exo-3,4-dichlorobicyclo [3.2.l]oct-2-ene to 3-chlorobicyclo[3.2.l]oct-2-ene, 51, 61... 

Sattelkau and Eilbracht90 have exploited the Claisen rearrangement of allyl vinyl ethers in their synthesis of several spiro compounds. As shown below in equation 62, 7,9-dimethyl-l,4-dioxa-spiro[4,5]decan-8-one, 118, was converted to a ,/J-unsaturated ester 119 which was reduced to allyl alcohol 120906. Allyl vinyl ether 121 underwent a rhodium-catalyzed Claisen rearrangement to afford 7r,13r-dimethyl-l,4-dioxa-(8rC9)-dispiro[4.2.4.2]tetradecan-10-one (122) in 36% yield. 

Redox Rearrangement of Allylic Alcohols to Chiral Aldehydes... 

Sigmatropic rearrangement of allylic sulfoxide to allylic alcohol. 

B. Enantioselective Access to Allylic Alcohols via Asymmetric Rearrangement... 

Enantioselective deprotonation.2 The rearrangement of epoxides to allylic alcohols by lithium dialkylamides involves removal of the proton syn to the oxygen.3 When a chiral lithium amide is used with cyclohexene oxide, the optical yield of the resulting allylic alcohol is 3-31%, the highest yield being obtained with 1. 

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