Studies of microwave-enhanced Suzuki-Miyaura vinylation of electron-rich sterically hindered substrates utilizing potassium vinyltrifluoroborate

Pd-Catalyzed Vinylation of Aryl Halides with Inexpensive Organosilicon Reagents Under Mild Conditions

Pd-catalyzed Hiyama vinylation reaction of non-activated aryl chlorides and bromides under mild conditions was developed. The use of efficient vinyl donors and electron-rich sterically hindered phosphine ligands was critical for the success of the reaction. The products of this transformation can be used for Am/Cm separation, an important challenge in nuclear fuel reprocessing. The substituent effect on Am/Cm separating selectivity was also achieved, which could contribute to the development of new chromatographic materials for the separation of Am and Cm.

Fast, greener and scalable direct coupling of organolithium compounds with no additional solvents

Although the use of catalytic rather than stoichiometric amounts of metal mediator in cross-coupling reactions between organic halides and organometallic counterparts improves significantly the atom economy and waste production, the use of solvents and stoichiometric generation of main-group byproducts (B, Sn and Zn) hamper the 'greenness' and industrial efficiency of these processes. Here we present a highly selective and green Pd-catalysed cross-coupling between organic halides and organolithium reagents proceeding without additional solvents and with short reaction times (10 min). This method bypasses a number of challenges previously encountered in Pd-catalysed cross-coupling with organolithium compounds such as strict exclusion of moisture, dilution and slow addition. Operational ease of this protocol combines the use of industrially viable catalysts loadings (down to 0.1 mol%), scalability of the process (tested up to 120 mmol) and exceptionally favourable environmental impact (E factors in several cases as low as 1).

Br···O contacts and π-π stacking dominate the packing in methyl 4-bromo-3,5-dimethoxybenzoate

The title compound, C10H11BrO4, a useful precursor to pharmaceutically active isocoumarin and isochroman derivatives, crystallizes with two unique molecules in the asymmetric unit. A π-π stacking interaction links the planar molecules in the asymmetric unit. Additional π-π contacts stack pairs of molecules along the c axis. A feature of the crystal packing is the presence of a number of short Br···O contacts. A particularly unusual arrangement involves the formation of dimers, with pairs of Br···O contacts imposing a close Br···Br interaction and generating five-membered rings within an eight-membered ring formed by two Br···O contacts. Only two comparable arrangements have been reported previously. The Br···O contacts combine with weak C-H···O hydrogen bonds to form corrugated sheets of molecules approximately parallel to (001). These sheets are stacked along the c axis by π-π interactions to generate a three-dimensional network.

Microwave assisted Suzuki-Miyaura and Ullmann type homocoupling reactions of 2- and 3-halopyridines using a Pd(OAc)2/benzimidazolium salt and base catalyst system

A number of novel benzimidazole derivatives 1-4 were synthesized and the catalytic activity of these compounds in a catalytic system consisting of a benzimidazolium salt/Pd(OAc)2/K2CO3 were investigated in the Suzuki-Miyaura and Ullmann type homocoupling reactions under microwave irradiation. We obtained both cross coupling and homocoupling products of pyridine and some side products such as dimethylaminopyridine and unsubstituted pyridine.