A highly
efficient, green palladium-catalyzed cyclocarbonylation
of 2-iodoanilines with acyl chlorides has been developed that proceeds
smoothly in a biomass-derived solvent 2-methyltetrahydrofuran with N,N-diisopropylethylamine as base at 100
°C under 20 bar of carbon monoxide using an 2-aminoethylamino-modified
MCM-41-anchored palladium acetate complex [2N-MCM-41-Pd(OAc)2] as a heterogeneous catalyst, yielding a wide variety of 2-substituted
4H-3,1-benzoxazin-4-one derivatives in good to excellent
yields. This supported palladium catalyst could be facilely obtained
by a two-step procedure from easily available starting materials and
readily recovered via a simple filtration process and recycled at
least 8 times without any apparent decrease in catalytic efficiency.
The developed methodology not only avoids the use of toxic solvents
such as tetrahydrofuran and dimethylformamide but also solves the
basic problem of expensive palladium catalyst recovery and reuse and
prevents effectively palladium contamination of the desired product.
A highly efficient and practical heterogeneous palladium-catalyzed carbonylative coupling of 2-iodoanilines with aryl iodides has been developed. The reaction occurs smoothly in toluene at 110 °C with N,N-diisopropylethylamine as base under carbon monoxide (5 bar) and offers a general and powerful tool for the construction of various valuable 2-arylbenzoxazinones with excellent atom-economy, high functional group tolerance, good to high yields, and easy recyclability of the palladium catalyst. The reaction is the first example of heterogeneous palladium-catalyzed carbonylative coupling for the preparation of diverse 2-arylbenzoxazinones from commercially easily available 2-iodoanilines and aryl iodides.
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