Alkenylation allyl esters

In 1987, Oppolzer and Gaudin reported an intramolecular version of the reaction of a tt-allylpalladium complex with an alkene. The reactions of various 2,6-octadienyl acetate derivatives were achieved in the presence of Pd(dba)2-PPhj at 70-80 C leading to 2-vinyl-1-alkenyUdenecyclopentane derivatives in yields ranging from 20% to 98% (Schemes 4 and 5). With one or two methyl groups attached at the alkenyl terminus, the acyclic alkeny-lallyl acetates under Pd(II) catalysis cycUzed to yield l-alkenyl-2-vinylcyclopentane derivatives (Scheme A 7r-allylpalladium intermediate generated from an allyl ester can... 

The reaction takes advantage of the ease with which the functionalized alkynes used as starting material can be prepared and of the fact that a number of aryl and alkenyl halides or triflates, alkyl halides, and allyl esters can successfully be used as carbon donors. In the presence of carbon monoxide, a three-component process can take place, widening the scope of the reaction and providing a useful, straightforward entry into cyclization products incorporating a molecule of carbon monoxide. 

Zhou W, Xu J, Zhang L, Jiao N (2011) An efficient approach to alkenyl nitriles from allyl esters. Synlett 7 887-890... 

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... 

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... 

The cross-coupling of alkynylzinc halides or fluorinated alkenylzinc halides with fluori-nated alkenyl iodides allows the preparation of a range of fluorinated dienes or enynes - Functionalized allylic boronic esters can be prepared by the cross-coupling of (dialkylbo-ryl)methylzinc iodide 428 with functionalized alkenyl iodides. The intramolecular reaction provides cyclized products, such as 429 (Scheme 109) ° °. In some cases, reduction reactions or halogen-zinc exchange reactions are observed. 

The addition of Grignard reagents or organolithiums (alkenyl, alkyl, alkynyl, allyl or aryl) to nitroenamines (281)213 was reported by Severin to afford P-substituted-a-nitroalkenes.214 b Similarly, ketone enolates (sodium or potassium), ester enolates (lithium) and lactone enolates (lithium) react to afford acr-nitroethylidene salts (294) which, on hydrolysis with either silica gel or dilute acid, afford 7-keto-a,(3-unsaturated esters or ketones (295)2l4c-d or acylidene lactones (296).214 Alternatively, the salts (294, X s CH2) can be converted to -y-ketoketones (297) with ascorbic acid and copper catalyst. 

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