Ru-mediated selective addition reactions of carboxylic acids to internal and terminal alkynes

Ruthenium(IV)-Catalyzed Markovnikov Addition of Carboxylic Acids to Terminal Alkynes in Aqueous Medium

“…All these results clearly demonstrate the extraordinary synthetic potential of trans -[RuCl 2 (η 3 :η 3 -C 10 H 16 )(PPh 3 )] ( 6a ). However, we must note that all attempts made to promote the addition of benzoic acid to alkynes bearing an internal CC bond (i.e., 3-hexyne and 4-octyne) using 6a were unsuccessful . In all cases, the starting materials were recovered unchanged ever after prolonged heating at 100 °C (24 h) in the presence of 5 mol % of 6a .…”

Synthesis of Pyridines from Ketoximes and Terminal Alkynes via C–H Bond Functionalization

“…Numerous transition-metal-mediated head-to-head dimerizations of alkynes have been developed as an atom-economical and expedient route to enynes, which are present in natural products and serve as handles for further synthetic elaboration. − Unfortunately, the very facility with which terminal alkynes dimerize has rendered their application as coupling partners problematic for a variety of transition-metal-mediated functionalizations. − In our previous attempts to employ terminal alkynes as coupling partners for pyridine synthesis alkyne dimerization proved competitive with the desired functionalization for both α,β-unsaturated N -benzylimines and oximes . Herein, we report an effective method for the synthesis of highly substituted pyridines via the C–H bond functionalization of α,β-unsaturated ketoximes with terminal alkynes through the use of inexpensive triisopropyl phosphite as a key ligand for minimizing alkyne homocoupling side reactions.…”

Metal–Ligand Cooperative Catalytic Coupling of Terminal Alkynes and Carboxylic Acids for the Stereoselective Synthesis of Dienyl Esters

“…To the best of our knowledge, no Ru–biscarbene complexes were observed when other Cp*Ru systems bearing coordinated phosphine ligands reacted with terminal alkynes (RCCH); ,− rather, the π-alkyne or vinylidene–Ru complexes were obtained similarly to our observations. Therefore, we may, likely, rule out a mechanistic scenario involving Ru–biscarbene as a key species in our system .…”