Synthesis and structural characterization of iridium(I) complexes of 20-membered macrocyclic rings bearing chelating bis(N-heterocyclic carbene) ligands

The reactivities of two 20-membered macrocyclic ligands, each containing two N-heterocyclic carbene (NHC) and two amine groups, towards [IrCl(COD)]₂ (COD is cycloocta-1,5-diene) were investigated. Macrocycles containing imidazolin-2-ylidene groups formed the monometallic complex [(1,2,5,6-η)-cycloocta-1,5-diene](5,16-dibenzyl-1,5,9,12,16,20-hexaazatricyclo[18.2.1.1^9,12]tetracosa-10,21-dien-21,22-diylidene)iridium(I) bromide dichloromethane monosolvate, [Ir(C₈H₁₂)(C₃₂H₄₂N₆)]Br·CH₂Cl₂, 2a. The structure of iridium complex 2a at 100 K has triclinic P-1 symmetry. The ligand in 2a coordinates to the Ir center through the NHC moieties in a cis fashion. Additionally, the ligand adopts an umbrella-like structure that appears to envelope the Ir center. The structure displays C-H...Br interactions. Macrocycles containing benzimidazolin-2-ylidene groups formed the bimetallic complex [μ-5,20-dibenzyl-1,5,9,16,20,24-hexaazapentacyclo[22.6.1.1^9,16.0^10,15.0^25,30]dotriaconta-10(15),11,13,25(30),26,28-hexaene-31,32-diylidene]bis{bromido[(1,2,5,6-η)-cycloocta-1,5-diene]iridium(I)}, [Ir₂Br₂(C₈H₁₂)₂(C₄₀H₄₆N₆)], 2b. The structure of complex 2b at 100 K has orthorhombic Pbca symmetry. Each NHC moiety in 2b coordinates in a monodentate fashion to an Ir(COD) fragment. The structure exhibits disorder of the main molecule. This disorder is found in the portion of the macrocycle containing an amine group. This structure also displays C-H...Br interactions. Finally, the structure of the hexafluorophosphate salt of the imidazolin-2-ylidene-containing macrocycle, namely 5,16-dibenzyl-1λ⁵,5,9,12λ⁵,16,20-hexaazatricyclo[18.2.1.1^9,12]tetracosa-1(23),10,12(24),21-tetraene-1,12-diium bis(hexafluorophosphate), C₃₂H₄₄N₆²⁺·2PF₆^-, 1c, was determined. The structure of macrocycle 1c at 100 K has triclinic P-1 symmetry and was found to contain C-H...F interactions.

Reaction condition controlled nickel(ii)-catalyzed C-C cross-coupling of alcohols

The challenge in the C-C cross-coupling of secondary and primary alcohols using acceptorless dehydrogenation coupling (ADC) is the difficulty in accurately controlling product selectivities. Herein, we report a controlled approach to a diverse range of β-alkylated secondary alcohols, α-alkylated ketones and α,β-unsaturated ketones using the ADC methodology employing a Ni(ii) 4,6-dimethylpyrimidine-2-thiolate cluster catalyst under different reaction conditions. This catalyst could tolerate a wide range of substrates and exhibited a high activity for the annulation reaction of secondary alcohols with 2-aminobenzyl alcohols to yield quinolines. This work is an example of precise chemoselectivity control by careful choice of reaction conditions.

Where does Au coordinate to N-(2-pyridiyl)benzotriazole: gold-catalyzed chemoselective dehydrogenation and borrowing hydrogen reactions

Pyridyltriazole gold(i) complexes proved to be an efficient precatalyst for the most challenging gold-catalyzed borrowing hydrogen reaction and dehydrogenation of alcohols and amines.

Synthesis, structures, photophysical and catalytic properties of benzothienyl iridium(III) complexes

Bisbenzothienyl iridium(III) complexes, [Ir(bt)2(PR3)]X (bt: 2-phenylbenzo[ d]thiazole, R = n-Bu or Ph, X = OTf, BF4 or SbF6) are reported, two of which, (R = n-Bu or Ph, X = OTf), have been characterised by X-ray crystallography. The complexes are thermally stable and their photophysical properties are presented, together with their catalytic activity in the “borrowing hydrogen reaction” of alcohols with amines.

C-Alkylation by Hydrogen Autotransfer Reactions

The development of practical, efficient, and atom-economical methods for the formation of carbon-carbon bonds remains a topic of considerable interest in current synthetic organic chemistry. In this review, we have summarized selected topics from the recent literature with particular emphasis on C-alkylation processes involving hydrogen transfer using alcohols as alkylation reagents. This review includes selected highlights concerning recent progress towards the modification of catalytic systems for the α-alkylation of ketones, nitriles, and esters. Furthermore, we have devoted a significant portion of this review to the methylation of ketones, alcohols, and indoles using methanol. Lastly, we have also documented recent advances in β-alkylation methods involving the dimerization of alcohols (Guerbet reaction), as well as new developments in C-alkylation methods based on sp (3) C-H activation.

Cu–Ag/hydrotalcite catalysts for dehydrogenative cross-coupling of primary and secondary benzylic alcohols

The development of new and inexpensive heterogeneous catalysts for direct C–C cross-coupling of primary and secondary alcohols is a challenging goal and has great importance in academic and industrial sectors.

Bifunctional Ru(ii) complex catalysed carbon–carbon bond formation: an eco-friendly hydrogen borrowing strategy

Bifunctional Ru(ii) complex (0.1 mol%) catalysed one-pot β-alkylation of secondary alcohols with primary alcohols and double alkylation of cyclopentanol were carried out successfully following the atom economical borrowing hydrogen methodology.

Benzimidazolin-2-ylidene N-heterocyclic carbene complexes of ruthenium as a simple catalyst for the N-alkylation of amines using alcohols and diols

Simple non-chelating ruthenium benzimidazolin-2-ylidene complexes as efficient N-alkylation catalysts using alcohols and diols following a hydrogen borrowing strategy.