Abstract
Transition metal-catalyzed carbonylation reactions have emerged as one of the most relevant synthetic approaches for the preparation of carbonyl-containing molecules. The most commonly used protocol for the insertion of a carbonyl moiety is the use of carbon monoxide (CO) but, due to its toxic and explosive nature, this process is not suitable at an industrial scale. More recently, the chemistry of CO surrogates has received large attention as a way to use less expensive and more environmentally friendly methods. Among the various CO surrogates, N,N-dimethylformamide (DMF) has been paid greater attention due to its low cost and easy availability. This mini-review gives appealing insights into the application of DMF as a CO surrogate in metal-catalyzed carbonylations; in particular, in the first part we will give a general state of the art of these reactions for the preparation of carbonyl-containing molecules; then, we will take into account all the various synthetic approaches for the metal-catalyzed carbonylative synthesis of heterocycles using DMF as a CO surrogate. Each protocol has been discussed critically in order to screen the best synthetic method and to offer perspective on trends and future directions in this field.
Highlights
Transition metal-catalyzed carbonylation reactions have emerged as one of the most relevant synthetic approaches for the preparation of carbonyl-containing molecules
It is clear that DMF in cyclocarbonylative reactions can act as a carbon monoxide (CO) surrogate through different reaction mechanisms: if under a pure palladium catalysis we found that the carbonyl group of DMF was directly the source of CO (Wu's protocols) [41,53], in this case the synergistic action of palladium and silver catalysis offered a very different pathway, where the methyl group of DMF was the source of the carbon atom of CO, while atmospheric O2
It is clear that DMF in cyclocarbonylative reactions can act as a CO surrogate through different reaction mechanisms: if under a pure palladium catalysis we found that the carbonyl group of DMF was directly the source of CO (Wu’s protocols) [41,53], in this case the synergistic action of palladium and silver catalysis offered a very different pathway, where the methyl group of DMF was the source of the carbon atom of CO, while atmospheric O2 was the source of the oxygen atom
Summary
The the synthesis of carbonyl-containing molecules has been reported, in most cases, in the the synthesis of carbonyl-containing molecules has been reported, in most cases, in the presence of of aapalladium palladium catalyst. Alterman et al, who described the aminocarbonylation of aryl bromides with. Alterman et al, who described the aminocarbonylation of aryl bromides with amines, in in the surrogate [28]. The substrate scope of this first work was quite limited: in DMF, acting as both solvent and reagent (Scheme 2). Pd-catalyzed aminocarbonylation aminocarbonylation of aryl aryl bromides bromides 11with withamines amines2,2,ininthe thepresence presenceofof as a surrogate, reported in by Alterman et al. DMF as a CO surrogate, reported in 2002 by Hallberg, Alterman et al [28]. Since it is well established that DMF, under heating, may decompose yield carbontomonoxide andmonoxide dimethylamine in the presence in of the basepresence [29], potasheating, maytodecompose yield carbon and dimethylamine of sium t-butoxide could promote this transformation under the MW heating. Imidazole can give a nucleophilic substitution to the ate 5,moiety affording a hydropalladium(II)
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