Palladium‐Catalyzed Carbonylative Synthesis of 2,3‐Disubstituted Chromones

Abstract

An unexpected palladium-catalyzed carbonylatives ynthesis of 2,3-disubstituted chromones has been developed. Startingf rom 2-bromofluorobenzenesa nd ketones,t he corresponding chromones were produced in good yields. By control experiments,this transformation was found to proceed through as equential carbonylation/Claisen-Hasse rearrangement/intramolecular nucleophilic aromatic substitution approach (S N Ar). More specifically,t he reaction sequence started with ap alladium-catalyzed carbonylation of the ketone with o-bromofluorobenzene to give the vinyl benzoates,w hich subsequently transformed into 1,3-diketones via aC laisen-Hasse rearrangement. Thef inal products were produced after an intramolecular S N Ar reaction of the in situ formed 1,3-diketone. Scheme 1. Pathways to 2,3-disubstituted chromones.Scheme 2. Thechemoselectivity on carbonylation of the deoxybenzoin substrate.

Ligand‐ and Solvent‐Tuned Chemoselective Carbonylation of Bromoaryl Triflates

“…and Heck et al., palladium‐catalyzed carbonylation, an efficient pathway for the constructing of carbonyl‐containing skeletons, has become a versatile tool in creating chemical diversity . Long‐lasting interests have been focused on the chemoselectivity of the palladium‐catalyzed carbonylation of one nucleophile bearing two nucleophilic sites (Scheme ), for example, the chemoselective carbonylation of aminophenols (alkoxycarbonylation vs. aminocarbonylation, Scheme a),– the selective carbonylative synthesis of 1,3‐diketones and vinylbenzoates from ketones with α‐hydrogen atoms (carbonylative α‐arylation vs. O ‐benzoylation, Scheme b)– and the base‐controlled tunable synthesis of linear‐ and angular‐fused quinazolinones with 2‐aminopyridine (two different nucleophilic nitrogen centers, Scheme c) …”

Heterocycle Synthesis through Pd‐Catalyzed Carbonylative Coupling

“…In 2016, 2,3‐disubstituted chromones 40 were obtained by a palladium‐catalyzed carbonylative route from 2‐fluoroaryl bromides and ketones (Scheme ) . Moderate to good yields (61–83 %) were achieved when substituted 1‐bromo‐2‐fluorobenzenes reacted with deoxybenzoin, as well as the reaction was able to tolerate the introduction of various substituents at different positions on both phenyl rings of deoxybenzoin (51–72 % yields, Scheme ).…”

Recent developments in carbonylation chemistry using [13C]CO, [11C]CO, and [14C]CO

“…Having a MOM‐protected phenol installed on the aryl ring ortho to the acyl group provided access to the 13 C‐labeled flavone‐derivative 72 through a Brønsted acid‐mediated cyclization. A related strategy was later reported relying on aryl bromides with an ortho ‐fluorine substitutent present . The initially formed 1,3‐diketone is set up for an intramolecular S N Ar reaction forming the 13 C‐labeled flavone 73 .…”