Carbon monoxide alkenyl derivatives

Acylzirconocene chloride derivatives are easily accessible in a one-pot procedure through the hydrozirconation of alkene or alkyne derivatives with zirconocene chloride hydride (Schwartz reagent) [Cp2Zr(H)Cl, Cp = cyclopentadienyl] and subsequent insertion of carbon monoxide (CO) into the alkyl— or alkenyl—zirconium bond under atmospheric pressure (Scheme 5.1) [2],... 

Alkenyl complexes. These complexes are prepared by reaction of an alkenyllithium with Cr(CO)6 followed by methylation. These a,(l-unsaturated complexes react with terminal alkynes to give, after oxidative work-up, phenols or quinones in which the acetylene group is ortho to the phenolic hydroxyl group derived from carbon monoxide. 

Acylzirconocene chlorides are easily accessible in a one-pot procedure through the hydrozirconation see Hydrozirconation) of alkene or alkyne derivatives with the Schwartz s reagent and subsequent migratory insertion see Migratory Insertion) of carbon monoxide into the alkyl- or alkenyl zirconium bond. The stability of the acylzirconocene chlorides is remarkable at room temperature, and consequently allows many applications in organic synthesis. 

The Pd(0)-catalyzed reactions of propargylic compounds so far discovered can be classified into four types, I, II, III, and TV, from a mechanistic viewpoint. The allenyl intermediate complex 8 undergoes three types of transformation, depending on reactants. The reactions of Type I proceed by insertion of unsaturated bonds into the a-bond between palladium and sp carbon in 8. This a-bond has a reactivity similar to the a-bond formed by the oxidative addition of alkenyl halides to Pd(0) in the Heck reaction [3]. Therefore, reactions similar to those observed in the Heck reaction are expected to occur witli the intermediate 8. Alkenes and carbon monoxide are known to insert into the palladium-carbon a-bond. The allene derivatives 9 are formed by these reactions (Scheme 11.3). 

Tamaru et a 1. The products (125) are produced in good yields from the alkenyl toluene-p-sulphonamides (124) and under mild conditions. In a related procedure, Pd1 -catalysed cyclization of the allenic amine derivatives (126) in the presence of carbon monoxide and... 

In solution at room temperature, the alkenyl compounds 127 evolve into mixtures of five products. However, under carbon monoxide atmosphere, they lead to the cyclic heterocarbene derivatives 129, probably, via the intermediates 128. Treatment of tetrahydrofuran solutions of 129 with LiCH3 at room temperature produces the deprotonation of the central CHPh carbon atom of the hetero-metalacycle and the formation of 130. In benzene as solvent, complexes 130 react with molecular hydrogen to yield the corresponding azabutadienes 132 and the well known dihydride-dihydrogen complex OsH2(il2-H2)(CO)(P Pr3)2 (131) [49]. 

Treatment of o-alkynylphenols with alkenyl triflates under the same conditions—potassium acetate and Pd(PPh3)4—under an atmosphere of carbon monoxide produces 2-substituted-3-acylbenzo[i ]furansf (Scheme 9). Depending on the substitution pattern of the reagents, variable amounts of 2-substituted-3-alkenylbenzo[( ]furans, 2-substituted-benzo[fc]furans, and 0-acyl derivatives of the starting alkyne have also been isolated. 

VI.2 Migratory Insertion Reactions of Alkyl-, Aryl-, Alkenyl-, and Alkynylpalladium Derivatives Involving Carbon Monoxide and Related Derivatives... 

Examples of sohd-bound Pd-catalyzed carbonylation of aryl and alkenyl halide, allyl alcohol, and derivatives are abundant in the literature. Polyketones have been obtained via carbonylation of ethylene and carbon monoxide catalyzed by palladium complexes of polysiloxane-bound phosphinet t or Pd(dppp) absorbed on alumina.f f Similar processes can also be carried out by catalyst formed simply by absorbing Pd(02CNEt2)2(NHEt2)2 onto silica geL Polyphosphine-bound palladium has been used to prepare ethyl hexanoate from 1-pentene, CO, and ethanol. Similar esterification of styrene has been achieved using a bimetallic system involving palladium and nickel immobilized on poly(Af-vinyl-2-pyrrolidone).f ... 

Aryl and alkenyl chromium carbene complexes react with HCaC(CH2)3CH=CHCH=CHR (R = C02Et, CH=CHC02Et) by insertion of carbon monoxide to give hydroquinones. Aryl molybdenum carbene complexes give hexahydroazulenes while alkenyl substituted molybdenum complexes generate hydroquinones or cyclopentadiene derivatives. ... 

In inert organic solvents nickel carbonyl reacts with diphenylacetylene to form tetraphenylcyclopentadienone and bis-tetraphenylc clopentadienone nickel (cf Fe(CO)5 p 229). In the presence of aqueous adds (e.g. acetic, hydrochloric) acetylenes are converted into a/3-unsaturated adds, e.g. acetylene itself yields acrylic add. With carbon monoxide under pressure, nickel carbonyl is continuously regenerated, so that the reaction becomes catalytic. The mechanism of this process is not yet understood, but it is found that water is essential. It is possible that formation of an intermediate <7-alkenyl nickel complex is involved, which affords the unsaturated add after carbonylation and hydrolysis of the acyl derivative ... 

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