Tribromomethyl ketone and tribromovinyl derivatives were selectively prepared from the decarboxylative tribromination. The reaction between propiolic acid derivatives and dibromoisocyanuric acid (DBCA)/H2O afforded predominantly a tribromomethyl ketone derivative in the presence of AgOAc (10 mol%). When the same reaction was conducted with 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO) instead of AgOAc, tribromovinyl derivatives were exclusively formed in good yields. It was found that ethynyl bromide is an intermediate.magnified image
A variety of arylalkynoic acids reacted with 1,3diiodo-5,5-dimethylhydantoin and HF•pyridine in the presence of AgOAc to provide the corresponding 1-fluoro-2,2-diiodovinylarenes in good yields and high regioselectivity. In addition, Pd-catalyzed cross-coupling reaction of 1-fluoro-2,2-diiodovinylarenes afforded diaryl coupling products in the Suzuki reaction and monoaryl coupling products with high stereoselectivity in the Hiyama reaction. It was found that C−Factivated borylation of fluoroalkenes using Pd catalyst afforded the vinylboranes with good yields.
2,2‐Dichloro‐1,2‐diarylethanones were synthesized from diarylalkynes and trichloroisocyanuric acid. The reaction was conducted in CH3CN/H2O at room temperature for 12 h. In addition, the desired 2,2‐dichloro‐1,2‐diarylethanones could be prepared from aryl bromides and propiolic acid through sequential Pd‐catalyzed decarboxylative coupling and chlorination. This method showed moderate to good yields and good tolerance toward functional groups such as chlorides, bromides, aldehydes, and ketones.
2,2,2-Trichloroacetophenone derivatives were synthesized via decarboxylative trichlorination from arylpropiolic acids and trichloroisocyanuric acid (TCCA). Ther eactionw as performed in the presence of water at room temperature,a nd the desired products were obtained in good yields.T he reaction showedg oodf unctional group tolerance towards halide,c yano,n itro,k etone,e ster anda ldehyde groups.I na ddition,t he 2,2,2-trichloroacetophenone derivatives were readily transformed into esters, amides,a nd hydrazides.B asedo ne xperiments with H 2 18 O( water-18 O), we proposedacationic reaction pathwaya st he mechanism and suggested two different pathways for producing aryl-and alkyl-substitutedpropiolic acids.
Transition metal-free Claisen-type condensation between two different amides was developed. N-phenyl-Ntosylbenzamide derivatives reacted with enolizable amides such as N-methyl pyrrolidinone and N,N-dimethyl acetamide in the presence of NaHMDS to give their corresponding β-ketoamides with moderate-to-good yields.
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