Electrochemical synthesis of 3,5-disubstituted isoxazoles

Electrochemically driven P–H oxidation and functionalization: synthesis of carbamoylphosphonates from phosphoramides and alcohols

Electrochemical synthesis of carbamoylphosphonates via P–H phosphorylation and oxygenation of phosphinecarboxamides with alcohols by using n-Bu₄NI (10 mol%) as an iodine source.

Oxidant-Free C(sp2)-H Functionalization/C-O Bond Formation: A Kolbe Oxidative Cyclization Process

An anodic oxidation/cyclization of 2-arylbenzoic acids for the synthesis of dibenzopyranones has been developed. The reaction proceeds at room temperature with no oxidant or electrolyte required and exhibits a high atom economy with H₂ being the only byproduct. A series of dibenzopyranones was obtained in good to excellent yields. Urolithins A, B, and C are formally synthesized by adopting this method as a key step to demonstrate its synthetic utility.

Synthetic Organic Electrochemical Methods Since 2000: On the Verge of a Renaissance

Electrochemistry represents one of the most intimate ways of interacting with molecules. This review discusses advances in synthetic organic electrochemistry since 2000. Enabling methods and synthetic applications are analyzed alongside innate advantages as well as future challenges of electroorganic chemistry.

Use of Electrochemistry in the Synthesis of Heterocyclic Structures

The preparation and transformation of heterocyclic structures have always been of great interest in organic chemistry. Electrochemical technique provides a versatile and powerful approach to the assembly of various heterocyclic structures. In this review, we examine the advance in relation to the electrochemical construction of heterocyclic compounds published since 2000 via intra- and intermolecular cyclization reactions.

Aerobic Oxidative Synthesis of 3,5-disubstituted Isoxazoles Directly from α,β-unsaturated Ketones

Using an efficient aerobic oxidative method, the synthesis of ten 3,5-disubstituted isoxazoles by treatment of α,β-unsaturated ketones with hydroxylamine and NaOH at room temperature has been achieved.

Mono- and Bisquinoline-Annulated Porphyrins from Porphyrin β,β'-Dione Oximes

An acid-induced reaction of meso-tetraphenyl-2-hydroxyimino-3-oxoporphyrin leads, with concomitant loss of water, to a formal electrophilic aromatic substitution of the ortho-position of the phenyl group adjacent to the oxime, forming a quinoline moiety. Owing in part to the presence of a π-extended chromophore, the resulting meso-triphenylmonoquinoline-annulated porphyrin (λmax = 750 nm) possesses a much altered optical spectrum from that of the starting oxime (λmax = 667 nm). An oxidative DDQ-induced ring-closure process is also possible, generating the corresponding meso-triphenylmonoquinoline-annulated porphyrin quinoline N-oxide, possessing a slightly shifted and sharpened UV-vis spectrum (λmax = 737 nm). The connectivity of the chromophores was conclusively shown by NMR spectroscopy. Both ketone functionalities in meso-tetraphenyl-2,3-dioxoporphyrin can be converted, via the oxime and using the acid- or oxidant-induced reaction pathways, either in one step or in a stepwise fashion, to bisquinoline-annulated porphyrin (λmax = 775 nm) and its N-oxide (λmax = 779 nm), respectively. This process is complementary to a previously established pathway toward bisquinoline-annulated porphyrins. Their zinc(II), nickel(II), and palladium(II) complexes are also described. Several examples of the quinoline-annulated porphyrins were crystallographically characterized, proving their connectivity and showing their conformations that are extremely distorted from planarity. The work presents a full account on the synthesis, structure, and spectroscopic properties of these classes of NIR-absorbing dyes.

Recent advances in the electrochemical construction of heterocycles

Due to the fact that the major portion of pharmaceuticals and agrochemicals contains heterocyclic units and since the overall number of commercially used heterocyclic compounds is steadily growing, heterocyclic chemistry remains in the focus of the synthetic community. Enormous efforts have been made in the last decades in order to render the production of such compounds more selective and efficient. However, most of the conventional methods for the construction of heterocyclic cores still involve the use of strong acids or bases, the operation at elevated temperatures and/or the use of expensive catalysts and reagents. In this regard, electrosynthesis can provide a milder and more environmentally benign alternative. In fact, numerous examples for the electrochemical construction of heterocycles have been reported in recent years. These cases demonstrate that ring formation can be achieved efficiently under ambient conditions without the use of additional reagents. In order to account for the recent developments in this field, a selection of representative reactions is presented and discussed in this review.