The cationic ruthenium-hydride complexes, [(PCy 3 ) 2 (CO)(CH 3 CN) 2 RuH] + BF 4 − and formed in situ from Ru 3 (CO) 12 /HBF 4 ·OEt 2 , were found to be highly effective catalysts for the C-H bond activation reaction of arylamines and terminal alkynes. The regioselective catalytic synthesis of substituted quinoline and quinoxaline derivatives was achieved from the ortho-C-H bond activation reaction of arylamines and terminal alkynes by using the catalyst Ru 3 (CO) 12 /HBF 4 ·OEt 2 . The normal isotope effect (k CH /k CD = 2.5) was observed for the reaction of C 6 H 5 NH 2 and C 6 D 5 NH 2 with propyne. A highly negative Hammett value (ρ = −4.4) was obtained from the correlation of the relative rates from a series of meta-substituted anilines m-X-C 6 H 4 NH 2 with σ p in the presence of Ru 3 (CO) 12 /HBF 4 ·OEt 2 (3 mol% Ru; 1:3 molar ratio). The deuterium labeling studies from the reactions of both indoline and acyclic arylamines with DC≡CPh showed that the alkyne C-H bond activation step is reversible. The crossover experiment from the reaction of 1-(2-amino-1-phenyl) pyrrol with DC≡CPh and HC≡CC 6 H 4 -p-OMe led to the preferential deuterium incorporation to the phenyl-substituted quinoline product. A mechanism involving rate-determining ortho-C-H bond activation and an intramolecular C-N bond formation steps via an unsaturated cationic rutheniumacetylide complex has been proposed.

The cationic ruthenium-hydride complex [(PCy3)2(CO)(CH3CN)2RuH]+BF4- (1) was found to be an effective catalyst for the regioselective coupling reaction of benzocyclic amines and terminal alkynes to form the tricyclic quinoline derivatives. The scope of the reaction was explored by using the catalytic system Ru3(CO)12/NH4PF6. The catalytically active cationic ruthenium-acetylide complex [(PCy3)2(CO)(CH3CN)2RuCCPh]+BF4- was isolated from the reaction of 1 with phenylacetylene.

General approaches for fluorination, trifluoromethylation, and trifluoromethylthiolation were developed based on the electrophilic nature of arynes. In these reactions, the addition of fluorine-containing nucleophiles onto aryne intermediates was efficiently promoted by either silver catalysts or silvercontaining stoichiometric reagents. Contrary to known methods that require aromatic precursors, our new approach enables efficient non-traditional synthesis of Ar-F, Ar-CF 3 and Ar-SCF 3 from nonaromatic building blocks under relatively mild conditions.Scheme 1 Unprecedented reactivity of arynes in the presence of a silver complex.

Arynes generated directly from alkyne building blocks in the presence of silver catalysts effectively activate primary, secondary, and tertiary alkane C-H bonds. This C-H insertion requires only a catalytic amount of silver complex and modest heating compared to harsh conditions and extra promoters including directing groups, oxidants, and bases in typical transition-metal-based C-H bond functionalizations. Preliminary mechanistic studies suggest that the C-H bond-breaking and new bond-forming events take place in a concerted manner, rendering a formal 1,2-addition of C-H bond across the π-bond of arynes.

[reaction: see text]. The cationic ruthenium complex [(PCy3)2(CO)(Cl)Ru=CHCH=C(CH3)2]+BF4- was found to be an effective catalyst for the coupling reaction of aniline and ethylene to form a approximately 1:1 ratio of N-ethylaniline and 2-methylquinoline products. The analogous reaction with 1,3-dienes resulted in the preferential formation of Markovnikov addition products. The normal isotope effect of k(NH)/k(ND) = 2.2 (aniline and aniline-d7 at 80 degrees C) and the Hammett rho = -0.43 (correlation of para-substituted p-X-C6H4NH2) suggest an N-H bond activation rate-limiting step for the catalytic reaction.

A systematic study of C-H insertion reactions with variously substituted and conformationally constrained substrates was carried out. High selectivity in the insertion between two competing C-H bonds caused by a strong stereoelectronic effect of an oxygen substituent was achieved. This regioselective C-H insertion reaction was employed as a platform to develop a concise asymmetric synthesis of platensimycin.

The regioselectivity in nucleophile trapping is investigated with arynes generated directly from bis-1,3-diynes. The regioselectivity is profoundly influenced by not only the nature of nucleophiles but also the substituents on the arynes, which is the consequence of both the unfavorable steric interaction between the incoming nucleophile and the nearby substituent and the inherent electronic bias induced by different substituents on the arynes.

Efficient Alder-ene reactions of various arynes generated directly from bis-1,3-diynes are described. The reactivity of ene donors with different tethers was examined under thermal and metal-catalyzed conditions, which indicates that both the formation of aryne intermediates and their ene reactions are less sensitive to the catalyst than to the structural features of the substrates.