Experimental Evidence for Zerovalent Pd(NHC) as a Competent Catalyst in C-N Cross-Coupling (NHC = DiMeIHept).

Use of the branched N-heterocyclic carbene (NHC) ligand 1,3-bis(2,6-bis(3-methyl-1-(2-methylpropyl)butyl)phenyl)-4,5-dichloro-1,3-dihydro-2-imidazole-2-ylidene (DiMeIHept) facilitated the stabilization of several relevant intermediates for Pd(NHC)-catalyzed C-N cross-coupling reactions. Complexes [Pd(DiMeIHept)](μ-N), [Pd(DiMeIHept)](μ-η-1,2-η-4,5-CH), and Pd(DiMeIHept)(pyridine), representing zerovalent Pd(NHC) bearing labile ligands, were isolated and structurally characterized, along with divalent PdCl(Ph)(DiMeIHept) and PdCl(Ph)(DiMeIHept)(-propylamine). The former is a 14-electron Pd complex, which is stable under air and chromatography on silica gel or neutral alumina.

Design and synthesis of novel main protease inhibitors of COVID-19: quinoxalino[2,1-]quinazolin-12-ones.

The COVID-19 pandemic represents a substantial global challenge, being a significant cause of mortality in numerous countries. Thus, it is imperative to conduct research to develop effective therapies to combat COVID-19. The primary aim of this study is to employ a two-step tandem reaction involving 2,3-dichloroquinoxaline and 2-amino--substituted benzamides in alkaline media/DMF at an elevated temperature to design and synthesize a series of polycyclic derivatives endowed with quinoxalino[2,1-]quinazolin-12-one framework.

(DiMeIHept)Pd: A Low-Load Catalyst for Solvent-Free (Melt) Amination.

, a hyper-branched N-aryl Pd NHC catalyst, has been shown to be efficient at performing amine arylation reactions in solvent-free ("melt") conditions. The highly lipophilic environment of the alkyl chains flanking the Pd center serves as lubricant to allow the complex to navigate through the paste-like environment of these mixtures. The protocol can be used on a multi-gram scale to make a variety of aniline derivatives, including substrates containing alcohol moieties.

Sodium Butylated Hydroxytoluene: A Functional Group Tolerant, Eco-Friendly Base for Solvent-Free, Pd-Catalysed Amination.

NaBHT (sodium 2,6-di-tert-butyl-4-methylphenolate), a strong, but hindered and lipophilic base, has been effectively paired with similarly lipophilic, high-reactivity Pd-NHC (N-heterocyclic carbene) catalysts to produce an ideal combination for performing solvent-free (melt) cross-coupling amination. The mild nucleophilicity of NaBHT, coupled with the anti-oxidant properties of its conjugate acid byproduct, BHT means the process seems to have no functional group incompatibilities. Highly effective coupling of base-sensitive and redox-active functional groups was observed in all cases with only 0.

Dismantling of Vinyl Ethers by Pentanuclear [(iPr P)Ni] H : Facile Cooperative C-O, C-C and C-H Activation Pathways.

The [(iPr P)Ni] H cluster (1) and H C=CHOtBu react at room temperature to form the new pentanuclear NiH carbide [(iPr P)Ni] H (C)(CO) (3), along with an equivalent of isobutylene. This transformation requires the activation of multiple unreactive bonds, including C-H, C-C, and C(sp )-O bond cleavage. Analysis of the reaction mixture by H NMR revealed the production of two additional paramagnetic species, assigned as [(iPr P)Ni] H (C-CH )NiOtBu (4 a) and [(iPr P)Ni] H (C-CH OtBu)NiOtBu (5 a), which arise from C(sp )-O bond cleavage and CH bond rearrangements.

Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts.

The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.