The first manganese-catalyzed aromatic C-H alkenylation with terminal alkynes is reported.The procedure features an operationally simple catalyst system containing commercially available MnBr(CO)₅ and dicyclohexylamine (Cy₂NH). The reaction occurs readily in a highly chemo-, regio-, and stereoselective manner delivering anti-Markovnikov E-configured olefins in high yields. Experimental study and DFT calculations reveal that: 1) the reaction is initiated by a C-H activation step via the cooperation of manganese and base; 2) manganacycle and alkynylmanganese species are the key reaction intermediates; 3) the ligand-to-ligand H-transfer and alkynyl-assisted C-H activation are the key steps rendering the reaction catalytic in manganese.

  

J. Am. Chem. Soc. 2013,135,1264.

We recently described a manganese-catalyzed dehydrogenative [4+2] annulation of N−Himines and alkynes, providing a highly atom-economic access to diverse isoquinolines. This transformation represents the first example of manganese-catalyzed C−H activation of imines, with its parent stoichiometric cyclomanganation reported in 1971. Theredox-neutral reaction produces H₂ as the major by-product and eliminates the need for any oxidants, external ligands or additives, thus standing out from known isoquinoline synthesis by transition-metal-catalyzed C−H activation. Mechanistic study revealed the 5-membered manganacycle and manganese hydride species as key reaction intermediates in the catalytic cycle.

Angew. Chem. Int. Ed. 2014, 53, 4950.

Mn-catalyzed expedient three-component synthesis of 1,5-amino/-keto alcohols from Grignard reagents, imines/nitriles, and tetrahydrofuran (THF) is described, which deviates from the classic Grignard addition to imines/nitriles in THF solvent. Moreover, THF was split and "sewn" in an unprecedented manner in the reaction leading to the formation of two geminal C–C bonds via C–H and C–O cleavage. Mechanistic experiments and DFT calculations revealed the intermediacy of radical and organomanganese species in the catalytic cycle and the α-arylative ring opening of THF as the key reaction step.

J. Am. Chem. Soc. 2014, 136, 6558.

A rhenium-magnesium co-catalyzed [4+2] annulation of benzamides and alkynes via C-H/N-H functionalization is described. The reaction features a divergent and high level of diastereoselectivities, which are readily switchable by subtle tuning of reaction conditions. Thus, a wide range of both cis- and trans-3,4-dihydroisoquinolinones are expediently synthesized in a highly atom-economical manner. Moreover, mechanistic studies unraveled a tandem mode of action between rhenium and magnesium in the catalytic cycles.

  

J. Am. Chem. Soc. 2013, 135, 4628.

We recently demonstrated a rhenium-catalyzed oxyalkylation of alkenes, where hypervalent iodine(III) reagents derived from wide-occurring aliphatic carboxylic acids were used as, for the first time, not only an oxygenation source but also an alkylation source via decarboxylation. The reaction also features a wide substrate scope, totally regiospecific difunctionalization, mild reaction conditions, and ready availability of both substrates. Mechanistic studies revealed a decarboxylation/radical-addition/cation-trapping cascade operating in the reaction.

  

J. Am. Chem. Soc. 2013, 135, 18048.