Merging Cu(I) and Cu(II) Photocatalysis: Development of a Versatile Oxohalogenation Protocol for the Sequential Cu(II)/Cu(I)-Catalyzed Oxoallylation of Vinylarenes

A sequential photocatalytic strategy is developed via the merger of Cu(II)/Cu(I)-catalytic cycles for the oxoallylation of vinyl arenes via α-haloketones. The initial Cu(II)-photocatalyzed oxohalogenation exploits ligand-to-metal charge transfer (LMCT) to generate halide radicals from acyl halides utilizing air as a terminal oxidant and can be employed for the late-stage modification of pharmaceuticals and agrochemicals. α-Bromoketones obtained this way can be subsequently subjected to a one-pot Cu(I)-photocatalyzed allylation. This sequential photocatalysis proceeds in a highly regio- and chemoselective fashion and is inconsequential to the electronic nature of styrenes.

Copper Cocatalyst Modulated Radical Generation for Selective Heterogeneous Photosynthesis of α-Haloketones

The α-haloketones are important precursors for synthetic chemistry and pharmaceutical applications; however, their production relies heavily on traditional synthetic methods via halogenation of ketones that are toxic and environmentally risky. Here, we report a heterogeneous photosynthetic strategy of α-haloketone production from aromatic olefins using copper-modified graphitic carbon nitride (Cu-C₃N₄) under mild reaction conditions. By employing NiX₂ (X = Cl, Br) as the halogen source, a series of α-haloketones can be synthesized using atmospheric air as the oxidant under visible-light irradiation. In comparison with pristine carbon nitride, the addition of Cu as a cocatalyst provides a moderate generation rate of halogen radicals and selective reduction of molecular oxygen into ^•OOH radicals, thus leading to a high selectivity to α-haloketones. The Cu-C₃N₄ also exhibits high stability and versatility, rendering it a promising candidate for solar-driven synthetic applications.

Recent Development in the Synthesis of Thiazoles

BACKGROUND

Thiazole-containing compounds are widely found in natural products as well as synthetic sources. Many thiazole-based compounds possess a broad spectrum of bioactivities and some of them are well-known drugs in the markets. The use of thiazole derivatives in other fields such as organic materials, cosmetics and organic synthesis has also widely reported. Due to a wide range of applicability, the synthesis of thiazole-containing compounds has attracted extensive interests of chemist and many studies in the synthesis of thiazole skeleton have been reported recently.

OBJECTIVE

This review article will discuss recent studies in the synthesis of thiazoles (from 2012). Beside the well-established Hantzsch thiazole synthesis, a large number of novel methods have been developed for the synthesis of thiazole derivatives. In most cases, reaction mechanisms have also been described.

CONCLUSION

The synthesis of thiazole derivatives has drawn great attention of chemists and many studies in the synthesis of these heterocycles have been reported recently. The classical method, the Hantzsch thiazole synthesis have still received great research interest of chemists. Moreover, many new methods have been established to synthesize thiazole-derived compounds. Unquestionably, more and more approaches to access thiazole skeleton will appear in the literature. Application of established methods for thiazole synthesis to the synthesis of drugs, organic materials, and natural products will probably paid attention.

One-Step Regioselective Synthesis of Benzofurans from Phenols and α-Haloketones

Reported here is the direct synthesis of naphthofurans and benzofurans from readily available phenols and α-haloketones promoted by titanium tetrachloride which combines Friedel–Crafts-like alkylation and intramolecular cyclodehydration into one step. This simple protocol allows for the formation of a variety of high value naphthofurans and benzofurans within which a series of cyclic and acyclic groups are readily incorporated. This process demonstrates the advantages of high levels of regioselectivity, broad substrate scope, and moderate to excellent yields.

β-Siloxy-α-haloketones through highly diastereoselective single and double mukaiyama aldol reactions

Double-action haloketones: A super silyl group enabled the first highly diastereoselective Mukaiyama aldol reactions of α-chloro- and α-fluoroketones with a wide range of aldehydes, providing anti-β-siloxy-α-haloketones. This process is compatible with one-pot double-aldol methodology and allows for rapid access to new halogen-modified polyketide fragments bearing up to four contiguous stereocenters.