Recent Developments on Photochemical Synthesis of 1,n-Dicarbonyls.

1,n-dicarbonyls are one of the most fascinating chemical feedstocks finding abundant usage in the field of pharmaceuticals. Besides, they are utilized in a plethora of synthesis in general synthetic organic chemistry. A number of 'conventional' methods are available for their synthesis, such as the Stetter reaction, Baker-Venkatraman rearrangement, oxidation of vicinal diols, and oxidation of deoxybenzoins, synonymous with unfriendly reagents and conditions. In the last 15 years or so, photocatalysis has taken the world of synthetic organic chemistry by a remarkable renaissance. It is fair to say now that everybody loves the light and photoredox chemistry has opened a new gateway to organic chemists towards milder, more simpler alternatives to the previously available methods, allowing access to many sensitive reactions and products. In this review, we present the readers with the photochemical synthesis of a variety of 1,n-dicarbonyls. Diverse photocatalytic pathways to these fascinating molecules have been discussed, placing special emphasis on the mechanisms, giving the reader an opportunity to find all these significant developments in one place.

Catalytic I2-moist DMSO-mediated synthesis of valuable α-amidohydroxyketones and unsymmetrical gem-bisamides from benzimidates.

We developed an efficient and straightforward I2-catalyzed strategy for the synthesis of functionalized α-amidohydroxyketones and symmetrical and unsymmetrical bisamides using incipient benzimidate scaffolds as starting materials and moist-DMSO as a reagent and solvent. The developed method proceeds through chemoselective intermolecular N-C-bond formation of benzimidates and the α-C(sp3)-H bond of acetophenone moieties. The key advantages of these design approaches include broad substrate scope and moderate yields. High-resolution mass spectrometry of the reaction progress and labeling experiments provided suitable evidence regarding the possible mechanism. 1H nuclear magnetic resonance titration revealed notable interaction between the synthesized α-amidohydroxyketones and some anions as well as biologically important molecules, which revealed a promising recognition property of these valuable motifs.

Addition of halide to π-bond directly from aqueous NaX solution: a general strategy for installation of two different functional groups.

Activation of π-bond with organic Lewis acid and cationic surfactant mediated direct transfer of halides to alkyne and alkene are demonstrated to afford α,α-dihaloketones and other valuable synthons with outstanding selectivities.

First synthesis of fused-Δ1-pyrrolines via intramolecular 1,3-dipolar cycloaddition of ketoimine: a complete diastereoselective approach.

Intramolecular formal 1,3-dipolar cycloaddition of ketoimine is developed with PhIO for the first synthesis of fused-Δ(1)-pyrrolines. The scope of the reaction, complete diastereoselectivity and its rationalization by a computational study are reported.

Generation of azomethine imine and metal-free formal 1,3-dipolar cycloaddition of imine with PhIO: reaction, scope, and synthesis.

Generation of azomethine imine and its scope in regioselective 1,3-dipolar cycloaddition (DC) of imine with PhIO toward highly substituted Delta(2)-1,2,4-triazoline, 1,2,4-triazole, and their fused, chiral, and sugar-based analogues are demonstrated.

Synthesis of glycal-based chiral benzimidazoles by VO(acac)2-CeCl3 combo catalyst and their self-aggregated nanostructured materials.

VO(acac)(2)-CeCl(3) combo catalyst has been developed for chemoselective cyclocondensation cum oxidation under mild reaction conditions toward synthesis of a new class of optically pure compounds, 2-(2'-C-3',4',6'-tri-O-benzyl/methyl-glycal)-1H-benzimidazoles. It involves an operationally simple synthetic protocol efficient for the syntheses of a wide range of chiral benzimidazoles in high yields without formation of undesired 1,2-disubstituted and pseudoglycal byproducts. Vanadium(V) is found as active oxidant for the chemical processes which is investigated by UV absorption spectroscopy. Highly ordered one-dimensional low molecular mass organic nanostructured materials are fabricated by nanocrystallization of the chiral nanoscale building blocks. Theoretical calculation by the B3LYP/6-31G** level of theory of the glycal-based chiral benzimidazoles shows out of planar geometry of the 1H-anthra[1,2-d]imidazole-6,11-dione moiety, which is responsible for the strong self-aggregation to generate ultralong nanostructured materials. We have also found nice agreement between the theoretical results with the experimental observation in 2D-NOESY experiments. The photophysical property of the solid nanostructured materials is also reported.

PhIO as a powerful cyclizing reagent: regiospecific [3+2]-tandem oxidative cyclization of imine toward cofacially self-aggregated low molecular mass organic materials.

The powerful cyclization and tandem oxidation property of environmentally benign PhIO is developed for the first time, which leads to regiospecific [3+2]-tandem oxidative cyclization of imine at room temperature in rapid access to a new class of compounds, 1,2-functionalized 4,5-diarylimidazoles, in excellent yield with synthetic efficiency. Size, shape, and activity of the involved nanoreactors for the green approach built up from various surfactants are investigated. Spontaneous generation of low molecular mass self-aggregated organic materials, their cofacial one-dimensional packing, and interesting photophysical properties are reported.

Generation of nitrile oxides under nanometer micelles built in neutral aqueous media: synthesis of novel glycal-based chiral synthons and optically pure 2,8-dioxabicyclo[4.4.0]decene core.

A highly efficient strategy for chemoselective oxidation of aldoximes to nitrile oxides by iodosobenzene in neutral aqueous media is reported. Their in situ intermolecular 1,3-dipolar cycloaddition (1,3-DC) with olefins in nanometer aqueous micelles occurs with improved stereoselectivity and acceleration of reaction rate toward synthesis of new chiral synthons, 3-(2'-C-3',4',6'-tri-O-benzylglycal)-Delta(2)-isoxazolines and others. Construction of optically pure 2,8-dioxabicyclo[4.4.0]decene skeleta is performed by this green approach, and the stereochemistry of the new chiral center is predicted by B3LYP density functional theory.