Transition metal–catalyzed coupling reactions have become one of the most important tools in modern synthesis. However, an inherent limitation to these reactions is the need to balance operations, because the factors that favor bond cleavage via oxidative addition ultimately inhibit bond formation via reductive elimination. Here, we describe an alternative strategy that exploits simple visible-light excitation of palladium to drive both oxidative addition and reductive elimination with low barriers. Palladium-catalyzed carbonylations can thereby proceed under ambient conditions, with challenging aryl or alkyl halides and difficult nucleophiles, and generate valuable carbonyl derivatives such as acid chlorides, esters, amides, or ketones in a now-versatile fashion. Mechanistic studies suggest that concurrent excitation of palladium(0) and palladium(II) intermediates is responsible for this activity.
We
describe the development of a general palladium-catalyzed carbonylative
method to synthesize acyl fluorides from aryl, heteroaryl, alkyl,
and functionalized organic halides. Mechanistic analysis suggests
that the reaction proceeds via the synergistic combination
of visible light photoexcitation of Pd(0) to induce oxidative addition
with a ligand-favored reductive elimination. These together create
a unidirectional catalytic cycle that is uninhibited by the classical
effect of carbon monoxide coordination. Coupling the catalytic formation
of acyl fluorides with their subsequent nucleophilic reactions has
opened a method to perform carbonylation reactions with unprecedented
breadth, including the assembly of highly functionalized carbonyl-containing
products.
We describe here the design of a palladium catalyzed route to generate aryl ketones via the carbonylative coupling of (hetero)arenes and aryl- or vinyl-triflates. In this, the use of the...
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