Synthesis of oxazole and furan derivatives via Rh₂(OAc)₄-catalyzed C≡X bond insertion of cyclic 2-diazo-1,3-diketones with nitriles and arylacetylenes

Abstract

A convenient and efficient procedure for the synthesis of 2-substituted-6,7-dihydrobenzo[d]oxazol-4(5H)-ones and 2-aryl-6,7-dihydrobenzofuran-4(5H)-ones through a Rh₂(OAc)₄-catalyzed C≡X (X = N, C) insertion of cyclic 2-diazo-1,3-diketones with nitriles and aromatic alkynes has been developed. This reaction uses readily available starting materials and stable cyclic 2-diazo-1,3-diketone compounds, with desired products formed in good to high yields. A tentative mechanism involving a C≡X bond insertion and 1,5-dipolar electrocyclization/ring opening and cyclization sequence for this reaction is proposed.

Graphical Abstract

Keywords:

• Cyclic 2-diazo-1,3-diketone
• electrocyclization
• furans
• insertion
• oxazoles

The work was partially supported by the National Natural Science Foundation of China (Nos. 21772001, 21372008), the Natural Science Foundation of Education Administration of Anhui Province (No. KJ2016A267), the Special and Excellent Research Fund of Anhui Normal University, and the Doctoral Scientific Research Foundation of Anhui Normal University (No. 2016XJJ110).