Mo^V Reagents in Organic Synthesis

Abstract

The use of Mo V reagents, and in particular MoCl 5 , in organic synthesis is surveyed. The oxidative treatment of aromatic substrates is the most common application. The unique properties of these reagents are due to their high oxidative power combined with exquisite Lewis acid properties. In several examples Mo V reagents outperform other common oxidative coupling reagents. C-C bond formation through inter-and intramolecular oxidative coupling can lead to selective formation of five-to eight-membered ring systems. Mechanistic investigations of the courses of reactions involving Mo V reagents and aromatic substrates indicate that radical cations are initially

Insights into the Scholl Coupling Reaction: A Key Transformation of Relevance to the Synthesis of Graphenes and Related Systems

“…We presumed that readily available chrysene derivatives[18a] could be converted into tetrabenzo[ a , cd , h , jk ]pyrenes by using the ubiquitous Scholl‐type oxidative coupling reaction (Scheme 1). In the event, the attempted cyclisation of 1a , 2a and 4a (see the Supporting Information for details), by using either FeCl 3 or MoCl 5 , resulted in the generation of intractable reaction mixtures, whereas those utilising DDQ/MeSO 3 H were much better behaved. Although this reagent combination apparently allowed the reaction to proceed with discrete C–C bond formation for substrates 1a and 4a , it was a process, which was again marred, in a practical sense, as product formation was also accompanied by irreproducible levels of mesylate incorporation…”

Electrochemical Arylation Reaction

“…Now, the next few described reactions focus on the electrochemical homocoupling reactions of arenes bearing hydroxyl groups at the aromatic compound. Here, one of the most powerful classes of reagents for the dehydrogenative coupling of aryls is represented by Mo­(V) reagents. − However, they have to be used in a stoichiometric manner which is not sustainable. When using molybdenum as an anode in HFIP a compact, conductive, and electroactive layer of higher valent molybdenum species is formed (see Scheme ).…”

Conformationally Restricted α, α Directly Linked BisBODIPYs as Highly Fluorescent Near-Infrared Absorbing Dyes

“…Then, we first utilized FeCl 3 in this reaction as an oxidant; however, no coupling product was detected, and most bisBODIPY 4a was decomposed (Table S1). MoCl 5 has been reported as an excellent single-electron oxidant that could be employed in several oxidative arylation reactions. , BisBODIPY 4a was then subjected to the MoCl 5 -promoted oxidative reaction. Interestingly, a slightly more polar cyan product (vs 4a ) was formed rapidly, which was further confirmed to be the directly fused bisBODIPY 5a by single-crystal X-ray analysis.…”