Oxidative cross-dehydrogenative coupling between N-aryl tetrahydroisoquinolins and 5H-oxazol-4-ones through two methodologies: copper catalysis or a metal-free strategy

Abstract

A direct oxidative cross-dehydrogenative coupling (CDC) of N-aryl tetrahydroisoquinolins with 5H-oxazol-4-ones catalyzed by CuBr using air as the only oxidant has been developed, which could also proceed smoothly under a metal-free oxidative system with PhI(OAc)2 as the oxidant. A series of alkylated tetrahydroisoquinolin derivatives were obtained in good yields and excellent diastereoselectivities.

Review on Asymmetric Catalysis Employing 5H‐Oxazol‐4‐Ones as α‐Hydroxy Carboxylic Acid Surrogates

“…Chiral metal‐complexes as catalysts investigated in the asymmetric reactions of 5 H ‐oxazol‐4‐ones include Mo(I), Ir(I), Zn(II), and Cu(I)‐complexes. In addition, there are two reports employing oxalactims as pronucleophiles in cross‐dehydrogenative coupling [19] and conjugate addition reactions [20] leading to corresponding racemate products. As evident from the literature reports, over the past two decades, 5 H ‐oxazol‐4‐ones have been extensively explored as pronucleophile/heterodiene in several asymmetric reactions.…”

Sustainable Synthetic Approach for (Pyrazol-4-ylidene)pyridines By Metal Catalyst-Free Aerobic C(sp2)–C(sp3) Coupling Reactions between 1-Amino-2-imino-pyridines and 1-Aryl-5-pyrazolones

“…In the recent years, cross-dehydrogenative coupling (CDC) reactions have received substantial interest. The major advancements made through studies in this area − have enabled CDC reactions to become highly attractive processes for formation of a variety of types of bonds. Particularly, interesting is the fact that these oxidative cross-coupling processes can be employed to form C–C bonds between two C–H components in an intermolecular − or intramolecular − manner.…”

Synthetic Strategy for Pyrazolo[1,5-a]pyridine and Pyrido[1,2-b]indazole Derivatives through AcOH and O2-Promoted Cross-dehydrogenative Coupling Reactions between 1,3-Dicarbonyl Compounds and N-Amino-2-iminopyridines

“…The elegant conceptual basis for and applications of cross-dehydrogenative coupling (CDC) reactions has greatly expanded in recent years. As a result, great progress has been made in developing new approaches for forming different types of bonds that are difficult to construct by using older classical methods. − The CDC concept has been employed to devise new strategies to construct an assortment of bonds as part of sequences to generate complex organic substances. An important example is C–C bond formation, which can be carried out using intramolecular − or intermolecular − CDC reactions between two C–H bond bearing moieties.…”

“…However, the methods developed for CDC to date usually require a catalyst to activate feebly reactive C­(sp 3 )–H bonds. The catalysts typically used for this purpose include complexes of transition metals, like copper (Cu), palladium (Pd), gold (Au), ruthenium (Ru), , iron (Fe), iridium (Ir),, vanadium (V), and cobalt (Co) . In addition, some of the CDC processes are activated by nonmetal catalysts, such as iodine, , rose bengal, 1,4-benzoquinone, phenyliodonium diacetate, and eosin …”