Rearrangement, allylic with vinyl epoxides

When the substrate is a vinylic epoxide, Grignard reagents generally give a mixture of the normal product and the product of allylic rearrangement (152). Butyllithium reacted with a difluoroalkylidene epoxide (F2C=CR epoxide) and Sn2 displacement gave alkylation at the difluoro carbon and opened the... 

On treatment with a palladium(O) catalyst, vinyl epoxides undergo facile unimolecular rearrangement to give dienols or enones depending on the substitution pattern of the substrate. In the presence of an active methylene compound in the reaction system, however, a single alkylation product is formed. Cyclic and acyclic vinyl epoxides participate equally well. The reaction proceeds with clean alkylation from the same face as the oxygen of the epoxide, and proceeds with allyl inversion (Scheme 22). ... 

Allylic fra i-l,2-azidohydrins prepared by Lewis-acid-catalysed ring opening of cyclic vinyl epoxides with sodium azide via an 5 2 mechanism have been found to isomerize to trans-l,4-azidohydrins via a suprafacial allyl azide [3,3]-sigmatropic rearrangement (Scheme 16). ... 

The radical-induced epoxide ring-opening of a,/3-epoxy-0-thiocarbonyl-imidazolides (23) [equation (3)] has been reported to be a convenient alternative to the Wharton rearrangement (action of hydrazine on epoxides of a,/3-unsaturated ketones) for production of allylic alcohols. /3,y-Disubstituted allylic alcohols with Z-conhguration are the major products formed on addition of alkyl-lithiums to the vinyl epoxide (24) [equation (4)]. ... 

Although some reactions, such as the transformation of -hydroxyalkyl selenides to -haloalkyl selenides (Scheme 161, b) or to vinyl selenides, enones (Scheme 161, 0. a,a-dihalocyclopropanes (Scheme 162, f) or p-hydroxyalkyl halides (Scheme 161, h Scheme 162, g), have bwn occasionally described or found only with specific types of -hydroxyalkyl selenides, especially those having a strained ring [e.g. their transformation to allyl selenides (Scheme 163, b), 1-selenocyclobutenes (Scheme 163, c) and cyclobutanones (Scheme 163, f),i2.i59,i60.i63] odiers are far more general. This is particularly the case of eir reductions to alcohols (Scheme 161, a Scheme 162, a Scheme 163, a Scheme 164, a Scheme 165, a) - or alkenes (Scheme 161, c Scheme 162, c Scheme 163, d Scheme 164, c Scheme 165, a Scheme 166, c), 89,i94,239 transformation to allyl alcohols (Scheme 161, e Scheme 162, b Scheme 164, b Scheme 166, b), - epoxides (Scheme 161, g Scheme 162, d Scheme 163, e Scheme 164, d Scheme 165, b Scheme 166, d) and rearranged carbonyl compounds (Scheme 162, e Scheme 164, e Scheme 165, a, c Scheme 166, e), - as well as oxidation to a-selenocarbonyl compounds (Scheme 161, d). 2 2.248-25i... 

Lithium derivatives of allyl silanes react in the y-position with alkyl halides, epoxides, and carbonyl compounds. The lithium derivative 110 of allyl silane 109 gives only the y-adduct 111 with ketones.31 Vinyl silanes such as 111 are usually converted into carbonyl compounds via epoxides which rearrange with Lewis acid catalysis and loss of silicon to give protected versions of ketones or aldehydes 112. 

While allyl and glycidyl ethers are converted into a mixture of oxetane and oxepine products with xec-butyllithium, Mordini and co-workers reported that allyl, benzyl, and propargyl epoxy ethers can be regioselectively converted into 2-vinyl, 2-phenyl, or 2-aIkynyl-3-(hydroxyalkyl) oxetanes upon treatment with either Schlosser s base or other mixed metal bases. Some of the best results were obtained with the LDA/potassium ferf-butoxide mixture (LIDAKOR, ref 194). While rearrangement of propargylic or benzylic epoxide ethers formed exclusively the four-membered oxetanes, rearrangements of allyl oxiranyl ethers show a selectivity for cyclization to the seven-membered ring. Trialkylsilyl-substituted epoxide allyl ethers also show a preference for the oxepine, and mixtures are obtained as the size of the silyl substituents is increased (Scheme 17). 

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