Abstract
In the presence of Cs2CO3, the first simple, efficient, and one-pot procedure for the synthesis of 3,5-diaryl pyridines via a variety of aromatic terminal alkynes with benzamides as the nitrogen source in sulfolane is described. The formation of pyridine derivatives accompanies the outcome of 1,3-diaryl propenes, which are also useful intermediates in organic synthesis. Thus, pyridine ring results from a formal [2+2+1+1] cyclocondensation of three alkynes with benzamides, and one of the alkynes provides one carbon, whilst benzamides provide a nitrogen source only. A new transformation of alkynes as well as new utility of benzamide are found in this work.
Highlights
Pyridine derivatives are one of the most important and fundamental six-membered nitrogen-heterocyclic compounds, and pyridine ring is the core structure in pharmaceutical compounds [1–4], and in natural products [5–7]
We are interested in the development of alkyne annulation protocols for the synthesis of carbo- and heterocyclic compounds in a one-step procedure [18–21], as well as in the construction of pyridine ring starting from alkynes catalyzed by transition-metal complexes (Scheme 1) [22–24]
Encouraged by our recent success in the development of base-promoted formation of C-N and C-O bonds and their applications in the synthesis of heterocyclic compounds [25–30], in this paper we report a new protocol for the one-pot formation of 3,5-diaryl pyridines from aromatic terminal alkynes and benzamide promoted by Cs2CO3 in sulfolane, the synthetic methods of 3,5-diaryl pyridines without use of alkyne have been recently reported [31–33]
Summary
Pyridine derivatives are one of the most important and fundamental six-membered nitrogen-heterocyclic compounds, and pyridine ring is the core structure in pharmaceutical compounds [1–4], and in natural products [5–7]. Encouraged by our recent success in the development of base-promoted formation of C-N and C-O bonds and their applications in the synthesis of heterocyclic compounds [25–30], in this paper we report a new protocol for the one-pot formation of 3,5-diaryl pyridines from aromatic terminal alkynes and benzamide promoted by Cs2CO3 in sulfolane, the synthetic methods of 3,5-diaryl pyridines without use of alkyne have been recently reported [31–33]. In this procedure, benzamides are firstly used as the nitrogen source to provide nitrogen atom only, and the reactions produce 1,3-diarylpropenes as the by-product
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