Allyl rearrangement intramolecular

Diallylsulfonium salts undergo intramolecular allylic rearrangement with strong bases to yield 1,5-dienes after reductive desulfurization. The straight-chain 1,5-dienes may be obtained by double sulfur extrusion with concomitant allylic rearrangements from diallyl disulfides. The first step is achieved with phosphines or phosphites, the second with benzyne. This procedure is especially suitable for the synthesis of acid sensitive olefins and has been used in oligoisoprene synthesis (G.M. Blackburn, 1969). 

This mechanism is exactly analogous to the allylic rearrangement mechanism for nucleophilic substitution (p. 421). The UV spectra of allylbenzene and 1-propenylbenzene in solutions containing NH2 are identical, which shows that the same carbanion is present in both cases, as required by this mechanism. The acid BH protonates the position that will give the more stable product, though the ratio of the two possible products can vary with the identity of BH". It has been shown that base-catalyzed double-bond shifts are partially intramolecular, at least in some cases. The intramolecularity has been ascribed to a conducted tour mechanism (p. 766) in which the base leads the proton from one carbanionic site to the other ... 

The first hydration step was promoted by Bronsted acids containing weakly or noncoordinating anions. In the second step, an intramolecular hydrogen transfer in the secondary alcohol was catalyzed by ruthenium(III) salts with chelating bipyridyl-type ligands. The possible complexation of the latter with the diene did not inhibit its catalytic activity in the allylic rearrangements, under acid-catalyzed hydration conditions. 

High levels of asymmetric induction can be achieved intramolecularly if the substrate functionality and the heteroatom ligand are contained in the same molecule. Chiral amido(a]kyl)cuprates derived from allylic carbamates [(RCH= CHCH20C(0)NR )CuR undergo intramolecular allylic rearrangements with excellent enantioselectivities (R = Me, n-Bu, Ph 82-95% ee) [216]. Similarly, chiral alkoxy(alkyl)cuprates (R OCuRLi) derived from enoates prepared from the unsaturated acids and trans-l,2-cyclohexanediol undergo intramolecular conjugate additions with excellent diasteroselectivities (90% ds) [217]. 

The 5-(2-alkenyloxy)thiatriazoles on thermal degradation gave alkenyl isocyanates by a presumed allylic rearrangement of the expected 2-alkenyl cyanates.54 Although the data do not exclude decomposition via intramolecular cyclic attack at the 4-position in the ring followed by very rapid decomposition of the 4-substituted thiatriazolines, these... 

Treatment of 2,4,6-triphenylpyrylium perchlorate with 3-benzo[i>]-thienylmethylmagnesium bromide affords the 4//-pyran (155),460 which undergoes allylic rearrangement in diethylene glycol in the presence of sodium to give the 2//-pyran (156).461 Under the same reaction conditions 156 is further converted by an intramolecular aldol condensation into 3-(2,4,6-triphenylphenyl)benzo[6]thiophene. 

Palladium-catalyzed allyl rearrangements can be considered special cases of allyl substitutions that occur intramolecularly. Hence, via the forma-... 

In a study of vinylcyclopropanes with tetranitromethane (TNM), from 1,1-divinylcyclopropane 156, a specific 1,4-diene, the unexpected product 118, was obtained. The formation of the nitronic ester was accompanied by homo-allylic rearrangement, followed by the intramolecular 1,3-dipolar cycloaddition (Equation 9) <2002DOC9>. 

An iridium(lll)-catalyzed tandem Claisen rearrangement-intramolecular hydroaryloxylation protocol has been described that allows the transformation of allyl aryl ethers to dihydrobenzofurans under mild conditions (Scheme 95) <2005TL1237>. An in rl/ -generated PPh3AuOTf complex also proved to be an efficient catalyst for this transformation <2006SL1278>. 

Gomez, A M, Valverde, S, Fraser-Reid, B, A route to unsaturated spiroketals from phenylthiohex-2-enopyranosides via sequential alkylation, allylic rearrangement, and intramolecular glycosidation,... 

A versatile and very powerful strategy for functional group transformation via allyl rearrangement involves intramolecular reactions of the 2,3- and 3,3-sigmatropic type, as exemplified in generalized form in Scheme 8. 

When there is the intention of effecting an allylic rearrangement in the C—C bond formation step, it is obvious that intramolecular processes are principally better than intermolecular ones as there always exists the competition of 5n versus Ss reactions with intermolecular processes, although there have been a number of improvements regarding this problem in recent years. Because of the huge amount of literature only selected examples, which demonstrate the general trends, can be presented here. 

Intramolecular displacement reaction of allylic acetate with amines has been applied to the synthesis of certain alkaloid skeletons such as desethylibogamine and ibogamine (183) as shown in Scheme 54 74. The reaction involves allylic rearrange-... 

An efficient method for the preparation of mono-heterocyclic compounds such as substituted tetrahydrofurans with high stereoselectivity via intramolecular SN2 O-cyclization of alkoxides has been reported. This is a nucleophilic displacement with a simultaneous allylic rearrangement (Scheme 321).1114... 

Allylboranes add to alkynes and electron-rich alkenes to give ds addition products through a six-center transition state and allylic rearrangement [42]. Allylboration of alkynes can be followed by cyclization though intramolecular allylboration of the terminal double bond. The cyclization proceeds slowly at room temperature and rapidly at 40-100 °C(eq (29)). 

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