Carbonyl bromide iodide

Carbonyl bromide iodide is predicted to be an unstable material with respect to isolation, dissociation or disproportionation reactions. Not surprisingly, no reports of its formation are extant. 

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Electrochemical reductive methods have also been used for carbonylative formation of acyltetracarbonyl anion formation with 1-halopentanes (bromides, iodides and chlorides) under anhydrous conditions with one equivalent of Fe(CO)5 the aldehyde is formed in respectable yields upon subsequent acidic workup (equation 209)421. 

The tendency to form the halocarbonyls as a frmction of the halide decreases in the seqnence Cl > Br > I. The carbonyl bromides of palladium(Il), Pd2Br4(CO)2, and gold, AnBr(CO), tend to decarbonylate in the solid state even under CO at atmospheric pressure, and the corresponding carbonyl iodides are unknown. 

Although Smh is more chemoselective than traditional dissolving metal reagents, it does react with sulfoxides, epoxides, the conjugated double bonds of unsaturated ketones, aldehydes and esters, alkyl bromides, iodides and p-toluenesulfonates. It does not, however, reduce carboxylic acids, esters, phosphine oxides or alkyl chlorides. In common with most dissolving metal systems, ketones with an a-hetero substituent suffer loss of the substituent rather than reduction of the carbonyl group. ... 

Numerous aryl bromides, iodides [203], borates [204] and triflates [205, 206] have been successfully carbonylated. Triflates could serve as a route for the synthesis of arenecarboxylic acid derivatives from phenols. This carbonylation using dppf in a catalytic mixture generally shows higher efficiency than PPhj or P(o-Tol)3 [207]. Poor performance is also noted for PPhj in a Pd-catalyzed vinyl substitution of aryl bromides [208]. Side-reactions involving the formation of [PPhjAr]Br and ArH are responsible. A system which is catalyzed effectively by PdCljfdppf) under 10 atm CO is the desulfonylation of 1-naphthalenesulfonyl chloride 58 in the presence of Ti(OiPr)4. Formation of isopropyl 1-naphthoate 59 can be explained in a sequence of oxidative addition, SOj extrusion, carbonylation and reductive elimination (Fig. 1-27) [209]. A notable side-product is di-l-naphthyl disulfide. 

Epoxides. The reaction of carbonyl compounds with methylene bromide (iodide) and magnesium amalgam gives methylenic olefins (2, 274) ... 

Allylation. Amalgamated Sm promotes reaction of allyl halides (bromide, iodide) with carbonyl compounds. Diallylation of esters occurs. ... 

This process is successful because the vinylic palladium intermediate is able to react in an intramolecular fashion with the neighboring ester group. This reaction most likely involves attack on the carbonyl oxygen, since a wide variety of different esters give similar results. In an analogous manner, vinylic chlorides, bromides, iodides, and triflates can be utilized to generate a-pyrones (Eq.37) [78-80]. 

As mentioned in the chapter on the reaction mechanism, the anion, especially of Ni-salts, is important in affecting the reaction course. The catalytic efficiency of the nickel halides strongly increases in the series fluoride, chloride, bromide, iodide [374—376]. The molar ratio of cobalt or nickel to iodine is also very important [414]. As in the hydroformylation reaction, metal carbonyls substituted by phosphine ligands are very reactive [377, 1009], and especially modified rhodium and palladium catalysts [1021, 1045] allow reactions under mild conditions. Thus, the nickel bromide triphenylphosphine allyl bromide complex shows an increased reactivity in the carbonylation of acetylenes. On the other hand, carbonyls substituted by phosphine ligands are also readily soluble in the reaction mixture [345, 377]. 

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