Allyl carbonates vinylation

Allylic acetates are widely used. The oxidative addition of allylic acetates to Pd(0) is reversible, and their reaction must be carried out in the presence of bases. An important improvement in 7r-allylpalladium chemistry has been achieved by the introduction of allylic carbonates. Carbonates are highly reactive. More importantly, their reactions can be carried out under neutral con-ditions[13,14]. Also reactions of allylic carbamates[14], allyl aryl ethers[6,15], and vinyl epoxides[16,17] proceed under neutral conditions without addition of bases. 

The term allylic refers to a C=C—C unit The singly bonded carbon is called the allylic carbon, and an allylic substituent is one that is attached to an allylic carbon Conversely doubly bonded carbons are called vinylic carbons, and substituents attached to either one of them are referred to as vinylic substituents... 

ADMET reaction. The 13C NMR spectrum also allows the scientist to distinguish between cis and trans internal sp2 carbons as well as the allylic carbons, which are adjacent to the internal vinyl position. Using quantitative 13C NMR analysis, the integration of the peak intensities between die allylic carbon resonances and diose of the internal vinyl carbons gives die percentage of trans/cis stereochemistry diat is present for the polymer.22 Empirically, the ratio of trans to cis linkages in ADMET polymers has typically been found to be 80 20. Elemental analysis results of polymers produced via ADMET demonstrate excellent agreement between experimental and theoretical values. 

Addition to linear 1,1-disubstituted allylic acetates is slower than addition to monosubstituted allylic esters. Additions to allylic trifluoroacetates or phosphates are faster than additions to allylic carbonates or acetates, and reactions of branched allylic esters are faster than additions to linear allylic esters. Aryl-, vinyl, alkynyl, and alkyl-substituted allylic esters readily undergo allylic substitution. Amines and stabilized enolates both react with these electrophiles in the presence of the catalyst generated from an iridium precursor and triphenylphosphite. 

Type III (no homodimerization) Acrylonitrile," protected 3° allylamines" Vinyl trialkoxysilanes, vinyl siloxanes 1,1-Disubstituted olefins, " non-bulky trisubstituted olefms, vinyl phosphonates, " vinyl phosphine oxides,phenyl vinyl sulfone, acrylonitrile, 4° allylic carbons (all alkyl substituents), protected 3° allylic alcohols, 7,Aolefm of 2-subst. 1.3- butadienes, 7,Aolefin of electronically deactivated 1.3- butadienes ... 

Type IV (spectators to CM) 1,1-Disubstituted olefms " 1,1-Disubstituted olefms, disub. o ,/ -unsaturated carbonyls, 4° allylic carbon-containing olefins, perfluorinated alkane olefins, 3° allylamines (protected)" Vinyl nitro olefins, protected trisubstituted allyl alcohols, a,/ -olefin of 2-subst. 1.3- butadienes, a,/ -olefm of electronically deactivated 1.3- butadienes ... 

The sp carbon of an alkene is called vinylic carbon, and an sp carbon that is adjacent to a vinybc carbon is called an allylic carbon. The two... 

When the Pd bears chiral ligands, these reactions can be enantioselective.1448 ir-Allylmo-lybdenum compounds behave similarly.1449 Because palladium compounds are expensive, a catalytic synthesis, which uses much smaller amounts of the complex, was developed. That is, a substrate such as an allylic acetate, alcohol, amine, or nitro compound1450 is treated with the nucleophile, and a catalytic amount of a palladium salt is added. The rr-allylpal-ladium complex is generated in situ. Alkene-palladium complexes (introducing the nucleophile at a vinylic rather than an allylic carbon) can also be used.1451... 

A carbon atom that is directly attached to a benzene ring is called a benzylic carbon (analogous to the allylic carbon of C=C—C). A phenyl group (C H —) is an even better conjugating substituent than a vinyl group (H2C=CH—), and benzylic carbocations and radicals are more highly stabilized than their allylic counterparts. The double bond of an alkenylbenzene is stabilized to about the same extent as that of a conjugated diene. 

The nickel-catalysed reaction of aryl, allyl or vinyl sulfides with Grignard reagents has been found to be an effective way for the conversion of carbon-sulfur bonds into carbon-carbon bonds [318]. However, simple aliphatic substrates are inert. 

The oxidative addition is quite general with alkyl, allyl, benzyl, vinyl, and aryl halides as well as with acyl halides to afford the palladium (II) complex VII. The frans-bis( triphenylphosphine )alkylpalladium halides can also be carbonylated in an insertion reaction to give the corresponding acyl complexes, the stereochemistry of which (17, 18) proceeds with retention of configuration at the carbon bonded to palladium. The acyl complex also can be formed from the addition of the corresponding acid halide to tetrakis (triphenylphosphine) palladium (0). 

Trimethylsilyl alkyl and aryl sulfides were found to function as latent sources of a sulfide nucleophile when used in conjunction with allyl carbonates or vinyl epoxides with Pd catalysts (equation 64).223... 

Trimethylsilyl alkyl and aryl sulfides react with allyl carbonates and vinyl epoxides to deliver the alkyl or aryl sulfide to the allyl unit. These species show typical regioselectivities by (i) adding to the less substituted end of alkyl substituted allyls (equation 290) (ii) adding to the allyl terminus more distant from remote oxygen functionality (equation 291) and (iii) showing substantial endocyclic addition to methylenecyclohexane-derived allyls (equation 292).223... 

A variety of other fragmentation reactions are potentially useful in the formation of carbon-carbon bonds, although none has yet shown the generality of the allyl- and vinyl-stannanes.146 In addition to the use of allyl sulfides discussed above (Scheme 41), allylcobalts have also been employed.147 Extensive... 

Essentially the same substituents as listed above may be present in the alkene being substituted, with the possible exception of chloro, alkoxy and acetoxy groups on vinyl or allyl carbons. These groups, especially chloro, may be lost or partially lost with palladium when the final elimination step occurs. For example, vinyl acetate, iodobenzene and triethylamine with a palladium acetate-triphenylphosphine catalyst at 100 C form mainly (E)-stilbene, presumably via phenylation of styrene formed in the first arylation step (equation 21 ).6 ... 

Scheme8.5. Palladium-catalyzed cross-coupling reactions of stannanes and other carbon nucleophiles with aryl, allyl, and vinyl bromides [56, 69-72],...

Regioselective polycondensations with transition-metal catalysts were also reported. Nomura et al. developed palladium-catalyzed allylation polycondensation, in which nucleophile predominantly reacted with jt-allyl palladium at the terminal allylic carbon to give fi-linear products [122,123]. On the other hand, polymerization with an iridium catalyst selectively proceeded at the internal allylic carbon to yield branched polymers with pendant vinyl groups (Scheme 30). These polycondensations demonstrate that polymers having different structures can be synthesized from the same monomers by changing the catalyst [124],... 

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