Nitrogen substituted cyclic enediynes: synthesis, thermal reactivity and complexation with metal ions

A number of N-substituted cyclic enediynes (azaenediynes) have been synthesized via Pd(0)-catalysed ene-yne coupling followed by N-alkylation. The simplest of them, a 10-membered monocyclic enediyne 1, underwent Bergman cyclization (BC) at 23°C with a half-life of 72 h. The kinetics of BC slowed down considerably by fusing a benzene ring onto the enediyne. Several novel bis(azaenediyne)s and bis(diazaenediyne)s 3-6 have been synthesized. Their onset temperatures for BC were lowered under metal ion complexation conditions

Mizoroki–Heck type reactions and synthesis of 1,4-dicarbonyl compounds by heterogeneous organic semiconductor photocatalysis

We report the synthesis of 1,4-dicarbonyl compounds and substituted alkenes (Mizoroki–Heck type coupling) starting from secondary and tertiary alkyl halides and vinyl acetate or styrene derivatives using visible-light photocatalysis. The protocol uses mesoporous graphitic carbon nitride (mpg-CN) as a heterogeneous organic semiconductor photocatalyst and Ni(II) salts as Lewis acid catalysts. Detailed post-characterization of the heterogeneous material has been carried out to support the proposed catalytic cycle. Apart from high functional-group tolerance, mild reaction conditions, scalability as well as easy recovery and reuse of the mpg-CN photocatalyst provide a practical solution to these widespread transformations in terms of sustainability and efficiency and this methodology is recommended for applications in academic and industrial synthesis

Photo-Ni dual catalytic C(sp2)–C(sp3) Cross-Coupling Reactions with Mesoporous Graphitic -Carbon Nitride as Heterogenous Organic Semiconductor Photocatalyst

The synergistic combination of a heterogeneous organic semiconductor mesoporous graphitic carbon nitride (mpg-CN) and a homogeneous nickel catalyst with visible-light irradiation at room temperature affords the C(sp(2))-C(sp(3)) cross-coupling of aryl halides and potassium alkyl trifluoroborates by single electron transmetallation. Like the homogeneously catalyzed protocol, the reaction is compatible with a variety of functional groups including electron-donating and electron-withdrawing aryl and heteroaryl moieties. Moreover, this protocol allows the installation of allyl groups onto (hetero)arenes, enlarging the scope of the method. The heterogeneous mpg-CN photocatalyst is easily recovered from the reaction mixture and reused several times, paving the way for larger-scale industrial applications of this type of photocatalytic bond-forming reactions

Organic semiconductor photocatalyst can bifunctionalize arenes and heteroarenes

Photoexcited electron-hole pairs on a semiconductor surface can engage in redox reactions with two different substrates. Similar to conventional electrosynthesis, the primary redox intermediates afford only separate oxidized and reduced products or, more rarely, combine to one addition product. Here, we report that a stable organic semiconductor material, mesoporous graphitic carbon nitride (mpg-CN), can act as a visible-light photoredox catalyst to orchestrate oxidative and reductive interfacial electron transfers to two different substrates in a two-or three-component system for direct twofold carbon-hydrogen functionalization of arenes and heteroarenes. The mpg-CN catalyst tolerates reactive radicals and strong nucleophiles, is straightforwardly recoverable by simple centrifugation of reaction mixtures, and is reusable for at least four catalytic transformations with conserved activity

The synthesis and reactivity of a novel 10-membered azaenediyne

Monocyclic azaenediyne 6 have been synthesized and has a half life of ~36 h in CDCl3 at 30°C

An Expeditious Route to Both Enantiomers of All Carbon Quaternary Stereocenters at C‑3 Carbon of Lactams via [3,3]-Sigmatropic Rearrangement: Total Synthesis of (−)-Physostigmine

A diastereoselective route to all carbon quaternary stereocenters at the C-3 position of cyclic lactams has been developed via Johnson–Claisen rearrangement of γ-hydroxy-α, β-unsaturated lactams. It has been observed that olefin geometry plays an important role in the development of the absolute stereochemistry of the product. The dependence of the product configuration on the olefin geometry is explained by postulating probable transition states. The success of this method has been shown for the multigram scale synthesis of these substituted lactams from commercially available cheap starting materials. The synthetic usefulness of this method is also demonstrated by carrying out the total synthesis of (−)-physostigmine

All-organic Z-scheme photoreduction of CO2 with water as the donor of electrons and protons

Carbon nitrides and flavins are two classes of easy accessible transition metal-free, photoactive materials. Their photocatalytic efficiency to enable a variety of chemical reactions is well documented. Here, we report on their combination in one photocatalytic system by designing biomimetic non-spherical core-shell architectures comprising micro-sized crystals of flavins decorated by potassium poly(heptazine imide) nanoparticles on the surface. The designed non-spherical core-shell composites are tested in the photocatalytic CO2 reduction to CH4, MeOH, EtOH and CO using water vapor as a donor of electrons and protons at the gas-solid interface. The forged Z-scheme heterojunction between these two materials allows increasing of their photocatalytic performance. Whereby excited states lifetimes are extended by interface charge recombination and photoredox processes are boosted because of an overall wider band gap