Abstract
An efficient transition-metal-based heterogeneous catalyst free procedure for obtaining the oxidative amidation of benzaldehyde using quinones as oxidizing agents in low molar proportions is described here. Pyrrolylquinones (PQ) proved to be more suitable than DDQ and 2,5-dimethylbenzoquinone to conduct the oxidation process. Although the solvent itself acted as the oxidant with low to moderate yields, PQ/DMSO provided an efficient system for carrying out the reaction under operational simplicity, mild reaction conditions, short reaction times and high yields of the desired product. The scope of the method was evaluated with substituted benzaldehydes and secondary amines. Theoretical foundations are given to explain the participation of quinones as an oxidizing agent in the reaction.
Highlights
Quinones, as for example 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDQ), are used as oxidizing agents in organic synthesis.[1]
We reported the attainment of a new group of uoride-recognizing quinone derivatives, the pyrrolyl quinones, from the natural product perezone and from 2,6dimethyl-1,4-dibenzoquinone 1.3 The anion recognition capabilities of these compounds suggested that in addition to generating radicals, the pyrrolyl quinones were de cient electron species capable of participating in oxidative addition reactions
This paper describes the use of pyrrolyl quinones (Scheme 1) as efficient oxidant in the oxidative amidation of benzaldehyde
Summary
As for example 2,3-dichloro-5,6-dicyano-1,4benzoquinone (DDQ), are used as oxidizing agents in organic synthesis.[1]. To give theoretical insights about the participation of quinones as oxidizing agent, proper forms of the Fukui functions,[20] f(r), have been calculated to describe the local reactive sites of the pyrrolyl quinones.
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