Regioselective Homolytic C2-H Borylation of Unprotected Adenosine and Adenine Derivatives via Minisci Reaction

A Minisci-type borylation of unprotected adenosine, adenine nucleotide, and adenosine analogues was successfully achieved through photocatalysis or thermal activation. Despite the challenges posed by the presence of two potential reactive sites (C2 and C8) in the purine motif, the unique nucleophilic amine-ligated boryl radicals effortlessly achieved excellent C2 site selectivity and simultaneously avoided the formation of multifunctionalized products. This protocol proved effective for the late-stage borylation of some important biomolecules as well as a few antiviral and antitumor drug molecules, such as AMP, cAMP, Vidarabine, Cordycepin, Tenofovir, Adefovir, GS-441524, etc. Theoretical calculations shed light on the site selectivity, revealing that the free energy barriers for the C2-Minisci addition are further lowered through the chelation of additive Mg2+ to N3 and furyl oxygen. This phenomenon has been confirmed by an IGMH analysis. Preliminary antitumor evaluation, derivation of the C2-borylated adenosine to other analogues with high-value functionalities, along with the CuAAC click reactions, suggest the potential application of this methodology in drug molecular optimization studies and chemical biology.

Non-Canonical Helical Structure of Nucleic Acids Containing Base-Modified Nucleotides

Chemically modified nucleobases are thought to be important for therapeutic purposes as well as diagnosing genetic diseases and have been widely involved in research fields such as molecular biology and biochemical studies. Many artificially modified nucleobases, such as methyl, halogen, and aryl modifications of purines at the C8 position and pyrimidines at the C5 position, are widely studied for their biological functions. DNA containing these modified nucleobases can form non-canonical helical structures such as Z-DNA, G-quadruplex, i-motif, and triplex. This review summarizes the synthesis of chemically modified nucleotides: (i) methylation, bromination, and arylation of purine at the C8 position and (ii) methylation, bromination, and arylation of pyrimidine at the C5 position. Additionally, we introduce the non-canonical structures of nucleic acids containing these modifications.

Recent developments in selective N-arylation of azoles

Transition-metal based carbon-heteroatom (C-X) bond formation has attracted the attention of synthetic chemists over the past few years because the resultant aryl/heteroaryl motifs are important substructures in many natural products, pharmaceuticals, etc. Several efficient protocols such as Buchwald-Hartwig amination, Ullmann coupling, Chan-Lam coupling and metal-free approaches have proved beneficial in C-X bond formation. Selective arylation of one hetero-centre over other centres without protection/deprotection thus allowing minimum synthetic manipulation has been achieved for several substrates using these protocols. Azoles are one such novel five-membered heterocyclic core with huge pharmaceutical applications. Though N-arylation on azole-bearing analogues has been extensively practised, selective N-arylation either on one N-centre or the exocyclic N-site of the azole ring in competition with other hetero-centres in the framework has been recently explored for azole-carrying systems. Thus, this review would focus on recent advances in chemo- and regio-selective N-arylation (either on one N-centre or the exocyclic N-site of the azole ring) on azole-containing frameworks.

Recent advances in the application of nano-catalysts for Hiyama cross-coupling reactions

This mini-review highlights the recent developments in the field of metal nanoparticle (NP) catalyzed Hiyama cross-coupling reactions.

Diaryl ethers synthesis: nano-catalysts in carbon-oxygen cross-coupling reactions

The diaryl ether moiety is not only prevalent in a significant number of natural products and synthetic pharmaceuticals but also widely found in many pesticides, polymers, and ligands. Ullmann-type cross-coupling reactions between phenols and aryl halides are regarded as one of the most important methods for the synthesis of this important and versatile structural motif. In recent years, the use of nano-sized metal catalysts in this coupling reaction has attracted a lot of attention because of these catalysts with their high surface-to-volume ratio, high surface energy, and reactive morphology allows for rapid C-O bond formation under mild and ligand-free conditions. In this review we will highlight the power of these catalysts in Ullmann-type C-O cross-coupling reactions.

C-H Imidation of 7-Deazapurines

We developed and presented here a ferrocene-catalyzed C-H imidation of 7-deazapurines (pyrrolo[2,3-d]pyrimidines) with N-imidyl peroxyesters. The reactions occur regioselectively at position 8 in 7-deazapurines, leading to a series of 8-succinimido-, phtalimido-, or naphthalimido-7-deazapurine derivatives. Attempted hydrazinolysis of resulting 8-imidyl-7-deazapurines led to corresponding 8-amino-7-deazapurine, which was very unstable and quickly decomposed.

Nanocatalysts for C–Se cross-coupling reactions

This mini review is an attempt to highlight the most important contributions toward the applications of nanocatalysts in carbon–selenium cross-coupling reactions with the emphasis on the mechanistic aspects of the reactions.

Recent advances in sulfur–nitrogen bond formation via cross-dehydrogenative coupling reactions

This focus-review surveys literature methods for the construction of sulfur–nitrogen bonds through cross-dehydrogenative coupling reactions between thiols and N–H compounds with a particular emphasis on the mechanistic aspects of the reactions. The literature has been surveyed until the end of 2017.

This review surveys the construction of sulfur–nitrogen bonds through cross-dehydrogenative coupling reactions between thiols and N–H compounds.

Regioselective C–H and N–H functionalization of purine derivatives and analogues: a synthetic and mechanistic perspective

This perspective provides a systematic and concise overview of the recent development in C–H/N–H bond functionalization in purine derivatives and analogues.

Chemoselective N-arylation of aminobenzamides via copper catalysed Chan–Evans–Lam reactions

Chemoselective N-arylation of unprotected aminobenzamides was achieved via Cu-catalysed Chan–Evans–Lam cross-coupling with aryl boronic acids for the first time.

Palladium-catalyzed C–H olefination of uracils and caffeines using molecular oxygen as the sole oxidant

The palladium-catalyzed oxidative C–H olefination of uracils or caffeines with alkenes using an atmospheric pressure of molecular oxygen as the sole oxidant has been disclosed.

Iodine-mediated thiolation of phenol/phenylamine derivatives and sodium arylsulfinates in neat water

An efficient and convenient protocol for iodine-mediated thiolation of phenols/phenylamines with sodium benzene-sulfinates in water has been achieved.

A copper(ii)–thioamide combination as a robust heterogeneous catalytic system for green synthesis of 1,4-disubstituted-1,2,3-triazoles under click conditions

One-pot synthesis of 1,4-disubstituted-1,2,3-triazoles 3 using copper(ii)–thioamide combination was reported.