Vinyl iodides carbonylation

Alkyl halides possessing / -hydrogens are usually poor substrates for carbonylative cross-coupling due to competitive / -hydride elimination/ Allyl chlorides can be used in carbonylative cross-coupling with allylstannanes/ phenyl-, 3-furyl, or vinylstannanes " to afford allylketones in modest to good yields. Divinylketones can be accessed through the reaction of vinylstannanes with vinyl iodides or vinyl triflates, with the latter requiring the addition of LiCl. Synthetic potential of this method has been proved in the formation of macrocyclic ketone jatrophone. In the reaction of vinyl triflates with tetramethyltin or aryltrimethylstannanes the additional activation by ZnCle is required. 

Since vinylic iodides (and bromides) can be catalytically carbonylated with a palladium catalyst, inter-molecular acylations sometimes can be carried out with appropriate halodienes and carbon monoxide as, for example, is shown in equation (45).107... 

Carbonylation of aryl and vinyl iodides.11 Pd-catalyzed carbonylation in a basic medium of aryl or vinyl iodides containing enolizable carbonyl groups can result in reaction with the in situ generated enolate to form enol esters or enol lactones. 

An intramolecular Heck-carbonylation/cyclization of the vinyl iodide 881 provides the 5,6-dihydropyran-2-one 882 during a total synthesis of manoalide (Equation 354) <1997CC1139>. The reaction of but-3-yn-l-ol with diaryl sulfides and carbon monoxide in the presence of a palladium(O) catalyst leads to a novel thiolactonization and hence arylthiosubstituted 5,6-dihydropyran-2-one 883 (Equation 355). Similar results are obtained with diaryl diselenides (Equation 355) <1997JOC8361>. Hydrozirconation of O-protected homopropargylic alcohols followed by carbonyla-tion and quenching with iodine provides a simple route to 5,6-dihydropyran-2-ones <1998TA949>. 

The application of organozinc iodides prepared in THF is illustrated in Protocols 4 and 5, which describe the palladium catalysed cross-coupling of a serine-derived organozinc iodide with a vinyl iodide, and the palladium catalysed carbonylative cross-coupling of another serine-derived organozinc iodide with a functionalized aromatic iodide. In the reaction with the vinyl iodide, it is important to transfer the solution of the organozinc iodide from the residual zinc, since this can react unproductively with the electrophile. In the case of the carbonylative coupling with the functionalized aromatic iodide, such a transfer is unnecessary, since the zinc does not react with the electrophile under the reaction conditions. These two protocols also illustrate how to conduct such reactions on different scales. 

Carbonylative couplings are also possible with vinyl iodides when reactions are conducted under CO pressure200. In these cases, double-bond isomerization occurs when vinyl-stannanes are used this is due to product isomerization rather than lack of stereospecificity of the coupling itself (equation 114). 

When Me3SiSnBu3 is treated with CsF, the fluoride anion should coordinate to the silyl group and not the stannyl group to produce a hypervalent silicate, and as a result, a stannyl anion would be generated.282 The stannyl anion reacts with vinyl iodide to produce a vinyl anion via a halogen-metal exchange and it reacts with the carbonyl group intramolecularly (Equation (113)). Aryl halides or allyl halides are also used in similar cyclizations.283,284... 

A direct way to a,p-unsaturated y-lactones involves the Pd-catalyzed carbonylation of cw-vinyl iodides (316 equation 110). In a similar way ejro-methylene lactones may be prepared from the al-kynols (318 equation 111). ... 

Ryu, Sonoda and coworkers reported that tris(trimethylsilyl)silane is a useful mediator for a three-component coupling reaction [45]. Table 4 summarizes examples of radical carbonylations mediated by (TMS)3SiH. The first example shows a three-component coupling reaction in which hexyl iodide, CO, and acrylonitrile combine to form a P-cymo ketone. The CO addition step is in competition with the addition to the alkene and the hydrogen abstraction from radical mediator. Thus, it is anticipated that a set of less efficient hydrogen donors, such as (TMS)3SiH, and the use of a smaller excess amount of an alkene is most favorable. Indeed, the reaction can be carried out at only 20 30 atm of CO pressure, substantially below the 80-90 atm which is used for carbonylative acyl radical reactions which are mediated by tin hydride, and a nearly stoichiometric amount (1.2 equiv) of acrylonitrile is sufficient. Some other examples, which include vinyl radical carbonylation, are also shown in Table 4. 

Carbonylative Carbon-Carbon Bond Formation. A general, mild (50 °C), and high yielding conversion of halides and triflates into aldehydes via Pd(Ph3P)4-catalyzed carbonylation (1-3 atm CO) in the presence of Tributylstannane has been described (eq 21). The range of usable substrates is extensive and includes Arl, benzyl and allyl halides, and vinyl iodides and triflates. The reaction has been extended to include ArBr by carrying out the carbonylation at 80 °C under pressure (50 atm CO), using poly(methylhydrosiloxane) (PMHS) instead of tin hydride. ... 

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