Metal catalyzed reactions for the formation of C(sp2)–O bonds have had a dramatic impact in natural product synthesis. They have enabled the emergence of new bond disconnections, which notably resulted in remarkably efficient and short synthetic pathways. The use of these reactions for the formation of C–O bonds in natural product synthesis is overviewed in this critical review.
Halogenated arenes and alkenes are of prime importance in many areas of science, especially in the pharmaceutical, agrochemical, and chemical industries. While the simplest ones are commercially available, some of them are still hardly accessible depending on their substitution patterns and the nature of the halogen atom. Reactions enabling the selective and efficient replacement of the halogen atom of an aryl or alkenyl halide by another one, lighter, or heavier, are therefore of major importance since they can be used for example to turn a less reactive aryl/alkenyl chloride into the more reactive iodinated derivatives or, in a reversed sense, to block an undesired reactivity, for late-stage modifications or for the introduction of a radionuclide. If some halogen exchange reactions are possible with activated substrates, they usually require catalysis with metal complexes. Remarkably efficient processes have been developed for metal-mediated halogen exchange in aryl and vinyl halides: they are overviewed, in a comprehensive manner, in this review article.
The copper-photocatalyzed borylation of aryl, heteroaryl, vinyl and alkyl halides( Ia nd Br) was reported. The reaction proceededu sing an ew heteroleptic Cu complex under irradiation with blue LEDs, givingt he corresponding boronic-acid esters in good to excellent yields. The reactionw as extended to continuous-flowc onditions to allow an easy scale-up. The mechanism of the reaction was studied and am echanism based on ar eductive quenching (Cu I /Cu I */Cu 0 )w as suggested.
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