Allylic ethers, alkenylation

Perfluoroallyl fluorosulfate is prepared by the treatment oiperfluoropropene with sulfur tnoxide m the presence of boron catalysts [2, 3, 4, 5, 6, 7] (equation 2) Perfluoroisopropyl allyl ether reacts similarly to give 58% polyfluoroallyl fluorosulfate in a cis/trans ratio of 6 4 [S] Sultones are the exclusive products without catalyst. Polyfluoroolefins such as 2-hydropentafluoropropylene [9], (2,3-dichloropropyl)tri-fluoroethylene [70], perfluoropropene [2, i], perfluoroisopropyl alkenyl ethers [S], and acyclic polyfluoroallyl ethers [77] undergo sulfur trioxidation to regioselectively produce the corresponding P-sultones in high yield... 

Intermolecular hydroalkoxylation of 1,1- and 1,3-di-substituted, tri-substituted and tetra-substituted allenes with a range of primary and secondary alcohols, methanol, phenol and propionic acid was catalysed by the system [AuCl(IPr)]/ AgOTf (1 1, 5 mol% each component) at room temperature in toluene, giving excellent conversions to the allylic ethers. Hydroalkoxylation of monosubstituted or trisubstituted allenes led to the selective addition of the alcohol to the less hindered allene terminus and the formation of allylic ethers. A plausible mechanism involves the reaction of the in situ formed cationic (IPr)Au" with the substituted allene to form the tt-allenyl complex 105, which after nucleophilic attack of the alcohol gives the o-alkenyl complex 106, which, in turn, is converted to the product by protonolysis and concomitant regeneration of the cationic active species (IPr)-Au" (Scheme 2.18) [86]. 

Nickel-bpy and nickel-pyridine catalytic systems have been applied to numerous electroreductive reactions,202 such as synthesis of ketones by heterocoupling of acyl and benzyl halides,210,213 addition of aryl bromides to activated alkenes,212,214 synthesis of conjugated dienes, unsaturated esters, ketones, and nitriles by homo- and cross-coupling involving alkenyl halides,215 reductive polymerization of aromatic and heteroaromatic dibromides,216-221 or cleavage of the C-0 bond in allyl ethers.222... 

Metallated allylic ethers can also be used as partners in allylzincations of alkenyl-metals144. Allyl methyl ether could be metallated with s-BuLi in ether provided that TMEDA was present and, after transmetallation with ZnBr2, addition to the alkenyl-lithium derived from 205 proceeded slowly at room temperature. Nevertheless, after hydrolysis the corresponding allylic ether 227 was obtained with high diastereoselectivity (equation 110)146. 

Not only an aryl group—as in Figure 14.46—but also an alkenyl group can participate in the Claisen rearrangement of allyl ethers (Figure 14.47). Allyl enol ethers are the substrates in this case. Figure 14.47 shows how this kind of allyl alkenyl ether (D) can be prepared from an... 

Isomerization. Allyl ethers and allyl acetals undergo isomerization to furnish the (Z)-alkenyl ethers with (dppblNiClj-LiBHEtj." On the other hand, the isomerization mediated by (PhjPljRuClj-LiBHEtj is almost totally stereorandom. 

Olefination and cyclopropanation. Preparation of alkenyl allyl ethers by the Wittig reaction is readily achieved. Tellurium and arsonium ylides tend to produce cyclopropyl ketones on reaction with enones. ... 

Reactions of the second type are carried out with palladium compounds or complexes of either bivalent or zero-valent states. Since these reactions proceed catalyti-cally without using reoxidants they are more useful than the stoichiometric processes. Telomerization of conjugated dienes, reactions of allylic and alkenyl esters and ethers, and various organic halides belong to this type. 

Aldol condensation, 111, 249 Aldoximes, 41, 42, 383 Alkali acetylides, 166 Alkamines, 261 Alkenyl bromides, 254 Alkyl azides, 403, 404 9-Alkylbicyclo[3.3.1JnonanoI-9, 31 Alkyl bromides, 254 Alkyl fluorides, 136 Alkyl halides, 133, 378 5-Alkyloxazolidones, 122 Alkylsulfenes, 103 Alkynes, 141, 248, 249 Alkynes, trimerization, 23 Allene, 388 AHenes, 274-276, 465 Allenyl ethers, 337 Allyl alcohol, 415 Allyl alcohols, 4)5 Allylailenes, 52 Allylamines, 326 Allyl bromide, 324 Allylcarbinyl chloride, 463 Allyl chloride, 109 Allyl ethers, 158... 

Alkenyl allyl ethers. A silyl enol ether nixed acetal of iodoacetaldehyde. The eliminaot BuLi furnishes the alkenyl allyl ether with a defi ractor is that the elimination pattern in DME is... 

Alkenyl allyl ethers. A silyl enol ether, an allylic alcohol, and NIS react to form mixed acetal of iodoacetaldehyde. The elimination of an iodine atom and the siloxy group with BuLi furnishes the alkenyl allyl ether with a defined (Z)- or ( )K onfiguration. An important factor is that the elimination pattern in DME is strictly anti, while in hexane it is syn. 

Allyl ethersr Hydrozirconation of alk> in the presence of ZnClj gives ( )-allyl ethers ThioaUylation Allylzirconium spec carbonyl compounds in an anh-selectise fashi (E)-2-Alkenyl-l,3,2-dioxaboroUdines. boration of 1-alkynes with pinacolborane. ih< a-bromo ketones. ... 

Between the two approaches presented in the above paragraphs, namely (i) the generation of an alkenyl function within the carbohydrate or (ii) its functionalization with a conventional monomer unit, a compromise option consists in introducing on hydroxyl functions a polymerizable unsaturation with a reduced number of atoms in the form of vinyl or allyl ether functions. 

Z)-1,3-Enyne compounds were synthesized by palladium(ll)-acetate-catalysed direct dehydrogenative alkenylation of terminal arylalkynes with unactivated allylic ethers. Various terminal arylalkynes can participate in the reaction, stereoselec-tively affording the desired conjugated (Z)-l,3-enynes in moderate to good yield l,3-bis(diphenylphosphino)propane was used as a ligand. ... 

Gyclization/hydrosilylation of enynes catalyzed by rhodium carbonyl complexes tolerated a number of functional groups, including acetate esters, benzyl ethers, acetals, tosylamides, and allyl- and benzylamines (Table 3, entries 6-14). The reaction of diallyl-2-propynylamine is noteworthy as this transformation displayed high selectivity for cyclization of the enyne moiety rather than the diene moiety (Table 3, entry 9). Rhodium-catalyzed enyne cyclization/hydrosilylation tolerated substitution at the alkyne carbon (Table 3, entry 5) and, in some cases, at both the allylic and terminal alkenyl carbon atoms (Equation (7)). 

Palladium-catalyzed asymmetric cyclization/hydrosilylation tolerated a number of functional groups including benzyl and pivaloyl ethers as well as benzyl and methyl esters (Table 8, entries 1-4). Furthermore, the protocol tolerated substitution at one of the two /ra/zi -terminal alkenyl positions and at one of the two allylic positions of the 1,6-diene (Table 8). As was the case with diene cyclization/hydrosilylation catalyzed by achiral palladium... 

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