Addition of acyl halides

Free-radical addition of acyl halides to alkenes... 

Addition of unsaturated boranes to methyl vinyl ketones Hydrocarboxylation of triple bonds Addition of acyl halides to triple bonds 1,4-Addition of acetals to dienes... 

An intermediate acylnickel halide is first formed by oxidative addition of acyl halides to zero-valent nickel. This intermediate can attack unsaturated ligands with subsequent proton attack from water. It can give rise to benzyl- or benzoin-type coupling products, partially decarbonylate to give ketones, or react with organic halides to give ketones as well. Protonation of certain complexes can give aldehydes. Nickel chloride also acts as catalyst for Friedel-Crafts-type reactions. 

Too-fast addition of acyl halides during preparation of ketones may lead to explosive reactions. 

The catalytic process (Figure 2-4) usually begins with the oxidative addition of an aryl halide or sulfonate onto the active form of the catalyst. In the presence of carbon monoxide the formed palladium-carbon bond breaks up with the concomitant insertion of a CO unit to give an acylpalladium complex. Such complexes might also be formed by the oxidative addition of acyl halides onto palladium. 

Addition of Acyl Halides (Addition of Halogen, Carbon)... 

Addition of halogens to ketenes 5-27 Addition of HOBr or HOC1 to triple bonds addition of chlorine acetate or other reagents to olefins 5-34 Addition of acyl halides to olefins... 

Addition of acyl halides to olefins in the presence of catalytic amounts of aluminum chloride, stannic chloride, or zinc chloride gives /3-halo ketones. An example is the addition of propionyl chloride to ethylene... 

A similar reaction has been reported by Stille et al. (251) using chiral alkyl halide. This reaction proceeds with inversion of configuration at carbon. The configuration was established by the rotation of the carbonylated complex which was also prepared by oxidative addition of acyl halide. 

Palladium chloride and metallic palladium are useful for carbonylating olefinic and acetylenic compounds. Further, palladium is active for decarbonylation of aldehydes and acyl halides. Homogeneous decarbonylation of aldehydes and acyl halides and carbonylation of alkyl halides were carried out smoothly using rhodium complexes. An acyl-rhodium complex, thought to be an intermediate in decarbonylation, was isolated by the oxidative addition of acyl halide to chlorotris(triphenylphosphine)rhodium. The mechanisms of these carbonylation and decarbonylation reactions are discussed. 

It is known that insertion of carbon monoxide to form an acyl complex is reversible, in which results depend on the pressure of carbon monoxide and temperature. If the above-mentioned mechanisms are correct, then acyl halides and aldehydes should be decarbonylated to form olefins provided that an acyl-palladium bond is formed by the oxidative addition of acyl halides or aldehydes to metallic palladium. This proved to be the case. When acyl halide was heated with a catalytic amount of metallic palladium or palladium chloride at 200°C. in a distilling flask, carbon monoxide and hydrogen halide were evolved rapidly, and olefin was collected in a good yield. This reaction is a new and useful preparative method of olefins. In the same way, aldehydes can be decarbonylated smoothly, but in this case, both olefin and the corresponding paraffin Were obtained. The latter probably arises by the hydrogenation of the olefin. Decarbonylation of certain aldehydes has been reported by several workers (3, 6), but no reasonable mechanism has been known. The mechanism of the palladium-catalyzed aldehyde formation discussed above gives clear explanation for the palladium catalyzed decarbonylation of aldehydes. 

To investigate the oxidative addition of acyl halides to a metal to form the acyl complex and to find a better decarbonylation agent, we selected chlorotris(triphenylphosphine) rhodium (XI) as a model complex. This complex is known to catalyze the oxo reaction (8) and the homogeneous hydrogenation of acetylenes and olefins (7, 28). 

By careful investigation of the reaction between acyl halides and chlorotris(triphenylphosphine) rhodium, we found that a new acylrho-dium complex (XIII) could be isolated in good yield. It forms by the oxidative addition of acyl halide, with the elimination of one mole of triphenylphosphine (25). This is the first example of acyl complex formation by direct oxidative addition of acyl halides. 

It would be more interesting and useful if the reaction could be made catalytic. Actually, catalytic decarbonylation reaction was found to be possible by using chlorocarbonylbis(triphenylphosphine) rhodium (XII) (26). This complex is reasonably stable, and more importantly it is four-coordinated and coordinatedly unsaturated, so that it may expand to a six-coordinated complex by the oxidative addition of acyl halides or aldehydes. The oxidative addition of methyl iodide to similar complexes was reported by Heck (5). 

Mori has reported a route to tetra- and penta-substituted pyrroles by a sequence involving reaction of the iminosilaacyl complex 5 with an alkyne in the presence of LiEt3BH to afford an initial azazirconacyclopentene intermediate <97CL825>. Addition of acyl halides and CuCl leads to the pentasubstituted pyrrole 6 or the desilylated product 7 in this one-pot reaction. 

In pyridine/water solution, the system making use of [Mn VMe(piperidine) Br] % sodium borohydride, and O2 produced a very small amount of cyclohexene oxide from cyclohexene. Similar systems involving different solvents, substrates and reducing agents failed to give evidence for autoxidation. The addition of acyl halides and acetic anhydride to these solutions in an effort to facilitate 0-0 bond cleavage by acylation also failed to produce detectable concentrations of products. ... 

Acylpalladiums are important intermediates of carbonylation reactions. Since similar acylpalladiums can be prepared directly by oxidative addition of acyl halides to... 

The addition of acyl halides to /rflns-[IrCl(CO)(PMe2Ph)2] also occurs with a /rani-stereochemistry as shown in (29) (Deeming and Shaw, 1969 Kubota and Blake, 1971 Collman and Sears, 1968). 

The oxidative addition of acyl halides (R COX) gives the m-dimethyl compounds (12), and hence the R COX addition has been trans. In contrast, allyl halides add in a cis fashion, to give the products (13). The... 

Acyl complexes can be prepared directly by oxidative addition of acyl halides to transition metal complexes with suitable electronic and geometric properties.23 The reactions of acetyl chloride with Wilkinson s catalyst, lRhCl(PPh3)3], are illustrative, Scheme 11.23 ... 

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