Catalytic Cleavage of Carbon Unreactive Bonds by the Coordination of a Directing Group

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(1)Catalytic reactions which involve the cleavage of an sp^3 C-H bond adjacent to a nitrogen atom in N-2-pyridynyl alkylamines are explored. The use of Ru_3(CO)_<12> as the catalyst results in the addition of the sp^3C-H bond across alkene bond to give the coupling products. A variety of alkenes, including terminal, internal, and cyclic alkenes, can be used for the coupling reaction. The presence of directing groups, such as pyridine, pyrimidine, and an oxazoline ring, on the nitrogen of the amine is critical for a successful reaction.(2)The reaction of pyrydinyl esters with HCOONH_4 in the presence of Ru_3(CO)_<12> resulted in decarbonylative reduction to give hydrocarbons. The use of organoboron compounds as a coupling partner resulted in cross-coupling reaction to give ketones, and no decarbonylation took place. A hydrosilane can also be used as a reducing reagent in place of HCOONH_4. A wide variety of functional groups are compatible for both reactions. The key step for both catal … More ytic reactions is the directing group-promoted cleavage of an acyl carbon-oxygen bond in esters, leading to the generation of acyl transition metal alkoxo complexes.(3)The direct carbonylation of C-H bonds in the benzene ring of N-phenylpyrazoles via catalysis by ruthenium or rhodium complexes was achieved. The reaction of N-phenylpyrazoles with carbon monoxide and ethylene in the presence of Ru_3(CO)_<12> or Rh_4(CO)_<12> resulted in the siteselective carbonylation of the ortho C-H bonds in the benzene ring to give the corresponding ethylketones. A variety of functional groups on the benzene ring can be tolerated. N-Phenylpyrazoles have higher reactivities than would be expected, based on the pKa values of the conjugate acid of pyrazole. The choice of solvent for this reaction is significant, and N, N-dimethylacetamide (DMA) gives the best result.(4)The reaction of alkenes with pyridinemethanol and CO in the presence of Rh_4(CO)_<12> resulted in hydroesterification under relatively mild reaction conditions. The use of benzyl alcohol in place of pyridinemethanol gave no reaction. Less