Direct Arylation of Heteroaromatic Compounds with Congested, Functionalised Aryl Bromides at Low Palladium/Triphosphane Catalyst Loading

Hybrid Phosphine/Amino-Acid Ligands Built on Phenyl and Ferrocenyl Platforms: Application in the Suzuki Coupling of o-Dibromobenzene with Fluorophenylboronic Acid

We describe the synthesis and characterization of two classes of hybrid phosphino ligands functionalized with amino ester or amino acid groups. These compounds are built either on a rigid planar phenyl platform or on a functionalized - conformationally controlled - rotational ferrocene backbone. Modifications at the -PR₂ phosphino groups (R=aryl and alkyl, with various steric bulk, Ph, Mes, i-Pr, Cy) and at the amino acid/amino ester functions are reported, showing a valuable high modularity. The coordination chemistry of these compounds regarding palladium and gold was investigated, in particular with respect to the coordination mode of the phosphino groups and the preferred interaction with metals for the amino ester and amino acid functions. For all the hybrid ligands, based either on ferrocenyl or phenyl platforms, the (P,N)-chelating effect dominates in solution for coordination to Pd(II), while linear P-Au(I) complexes without interaction with the amino groups are assumed. The investigation of the catalytic activity of these new ligands in the demanding palladium-catalyzed Suzuki-Miyaura coupling of o-dibromoarenes with fluorophenylboronic acid underlined the importance of the amino ester dicyclohexylphosphinoferrocene for avoiding the deleterious homocoupling and arene oligomerization side-reactions that were otherwise observed with the other phosphine ligands.

Pd-Catalyzed Cross-Couplings: On the Importance of the Catalyst Quantity Descriptors, mol % and ppm

This Review examines parts per million (ppm) palladium concentrations in catalytic cross-coupling reactions and their relationship with mole percentage (mol %). Most studies in catalytic cross-coupling chemistry have historically focused on the concentration ratio between (pre)catalyst and the limiting reagent (substrate), expressed as mol %. Several recent papers have outlined the use of “ppm level” palladium as an alternative means of describing catalytic cross-coupling reaction systems. This led us to delve deeper into the literature to assess whether “ppm level” palladium is a practically useful descriptor of catalyst quantities in palladium-catalyzed cross-coupling reactions. Indeed, we conjectured that many reactions could, unknowingly, have employed low “ppm levels” of palladium (pre)catalyst, and generally, what would the spread of ppm palladium look like across a selection of studies reported across the vast array of the cross-coupling chemistry literature. In a few selected examples, we have examined other metal catalyst systems for comparison with palladium.

Ni/NHC catalysis in C–H functionalization using air-tolerant nickelocene and sodium formate for in situ catalyst generation

A facile method for Ni/NHC catalyzed C–H alkylation and alkenylation of heteroarenes with alkenes and internal alkynes using air-tolerant nickelocene, sodium formate and NHC·HCl salts for in situ catalyst generation has been developed.

A sterically congested 1,2-diphosphino-1′-boryl-ferrocene: synthesis, characterization and coordination to platinum

A unique tritopic (P, P, B)-ferrocene ambiphile with antagonist functions directly attached to a metallocene backbone is described.

A general diastereoselective synthesis of highly functionalized ferrocenyl ambiphiles enabled on a large scale by electrochemical purification

A diastereoselective modification of tert-butylated ferrocenes leads to highly functionalized constrained ambiphiles (P,B or N,B) and hybrids (P,N or P,P′) on a multigram scale by a smart electrochemical purification.

Connecting Direct C-H Arylation Reactions with Dye-Sensitized Solar Cells: A Shortcut to D-A-π-A Organic Dyes

A step-economical synthetic strategy is developed to target thieno[3,4-c]pyrrole-4,6-dione (TPD)-based D-A-π-A organic dyes for dye-sensitized solar cells (DSSCs). Through sequential Pd-catalyzed direct C-H (hetero)arylation reaction, synthesis of the push-pull-type small molecules is reduced from the traditional six steps to two steps. In this report, we focus on the optimization of the key C-H monoarylation of TPD by screening ligands, acid additives, bases, and solvents. The reaction proves versatile toward new D-A-π-A organic dyes with a variety of different donor groups, and several derivatives are efficiently prepared under optimum reaction conditions. The sensitive aldehyde functionality that is a required intermediate for conversion into anchoring groups for TiO2 is well tolerated. Based on our synthetic study, DSSCs are fabricated and characterized using two designed sensitizers. The photovoltaic characterization of the devices affords an open-circuit voltage of 0.60-0.69 V, a short-circuit current density of 10.85-11.07 mA cm(-2), and a fill factor of 69.9-70.8 %, which corresponds to an overall power conversion efficiency of 4.61-5.33 %.

Modular functionalized polyphosphines for supported materials: previously unobserved31P-NMR «through-space» ABCD spin systems and heterogeneous palladium-catalysed C–C and C–H arylation

Functionalized modular polyphosphines introduce a conceptual novelty in controlling both implantation and conformation of donors in immobilized catalysts.

Pd-catalyzed direct C–H arylation of thieno[3,4-c]pyrrole-4,6-dione (TPD): a step-economical synthetic alternative to access TPD-centred symmetrical small molecules

A viable synthetic alternative for the facile construction of various thieno[3,4-c]pyrrole-4,6-dione (TPD)-based π-functional small molecules through direct C–H arylations has been demonstrated.

N-Heterocyclic carbene-palladium catalysts for the direct arylation of pyrrole derivatives with aryl chlorides

New Pd–NHC complexes have been synthesized and employed for palladium-catalyzed direct arylation of pyrrole derivatives by using electron-deficient aryl chlorides as coupling partners. The desired coupling products were obtained in moderate to good yields by using 1 mol % of these air-stable palladium complexes. This is an advantage compared to the procedures employing air-sensitive phosphines, which have been previously shown to promote the coupling of aryl chlorides with heteroarenes.