De novo design and synthesis of dipyridopurinone derivatives as visible-light photocatalysts in productive guanylation reactions

Electrochemical NaI-mediated one-pot synthesis of guanidines from isothiocyanates via tandem addition-guanylation

In this study, we present an electrochemical approach for the synthesis of guanidines from isothiocyanates and amines in a single reaction vessel. This one-pot operation takes place in aqueous media, utilizing an undivided cell setup with NaI serving as both the electrolyte and mediator. The process involves the in situ generation of thiourea, followed by electrolytic guanylation with amines. Under ambient temperature conditions, we successfully demonstrated the formation of 30 different guanidine compounds, achieving yields ranging from fair to excellent. Furthermore, the synthesis method could be carried out on a gram scale with a good yield. This protocol stands out for its cost-effectiveness, step-economical design, high tolerance towards various functional groups, and environmentally friendly reaction conditions.

Electrocatalytic Desulfurizative Amination of Thioureas to Guanidines

Guanidine has been known as an important class of N-containing molecules with a wide range of applications. Described here is a selective and efficient electrochemical approach to the synthesis of guanidines from easily accessible thioureas and amines. The key to success for this reaction is the in situ generation of a hypervalent iodine reagent as a catalyst from iodoarene by anodic oxidation. This mild desulfurizative amination presents ample substrate scope and good functional group tolerance without the use of extra stoichiometric chemical oxidants. As only electrons serve as the oxidation reagents, this method offers a more straightforward and sustainable manner toward versatile guanidines, including late-stage functionalization of pharmaceutically relevant molecules.

Anion Cascade Reactions II: Synthesis of 3-Isoquinuclidone-Based Bridged Polycyclic Lactams

A facile and convenient anion cascade strategy was developed for the synthesis of bridged-ring amides in moderate to excellent yields in one step in the presence of tBuOK in EtOH under mild conditions, starting from various cheap and commercially available 2-cyanoacetamides and precisely designed straight-chain and annular 1,4-dienones. This simple protocol was generally applicable to a wide range of substrates with high chemical conversion and diastereoselectivity.

Rh(III)-Catalyzed Oxidative Domino C-H/N-H Annulation: Diarylureas as Arylamine Donors for the Assembly of Indolo[2,1-a]isoquinolines

An efficient and convenient Rh(III)-catalyzed double aryl C(sp2)-H bond and N-H activation and annulation reaction is reported for the synthesis of indolo[2,1-a]isoquinolines in the presence of the Cu(OAc)₂ oxidant under heating conditions. Distinct from previous works with other arylamine donors, one molecule of 1,3-diarylurea can serve as a precursor of two molecules of arylamine in the reaction with diaryl-substituted alkynes.

Base-mediated [3 + 2]-cycloannulation strategy for the synthesis of pyrazolo[1,5-a]pyridine derivatives using (E)-β-iodovinyl sulfones

Pyrazolo[1,5-a]pyridines continue to occupy a special place in medicinal chemistry, but the direct construction of 3-sulfonyl analogues remains unexplored. Under basic conditions, pyridinium-N-amine and the corresponding dipolar aminide played a vibrant role in [3 + 2]-cycloaddition using (E)-β-iodovinyl sulfones. K₂CO₃-mediated tandem cycloannulative-desulfonylation of (E)-β-iodovinyl sulfones with 1-aminopyridinium iodide is realized to access 2-substituted pyrazolo[1,5-a]pyridines in good to high yields. An essential modification of the dipolar N-tosylpyridinium imide allows the first preparative synthesis of 3-sulfonyl-pyrazolo[1,5-a]pyridines in moderate to high yields. Of note, the metal-free protocol features a broad substrate scope with good functional group tolerance and compatibility. The efficacy of the process was proved with gram-scale reactions, and a plausible mechanism is also presented based on concrete results.

2,11-Dimethoxyldipyridopurinone as an efficient reducing visible-light photocatalyst for organic transformations

2,11-Dimethoxyldipyridopurinone (DP4) was demonstrated as a potent reducing visible-light PC that can efficiently catalyze three prototypic photoreactions: the redox-neutral, net oxidative and reductive reactions via oxidative-quenching mechanisms.