Development of a Mild and Versatile Directed Cycloaddition Approach to Pyridines |
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Authors: | Sylvestre P. J. T. Bachollet Dean C. Cocker Harry Adams Prof. Joseph P. A. Harrity |
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Affiliation: | Department of Chemistry, University of Sheffield, Brook Hill, Sheffield, S3 7HF (UK) |
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Abstract: | The aza‐Diels–Alder cycloaddition of 1,2,4‐triazines with alkynes offers a rapid and convenient method for the synthesis of highly substituted pyridines, but often requires harsh conditions and long reaction times. The present study offers a solution to these limitations by use of a temporary tether established by a Lewis acid–base complexation of in situ generated alkynylboranes and triazines bearing a Lewis basic donor. The cycloaddition reactions take place within 20 min at 40 °C and provide direct access to a broad range of pyridines with complete and predictable regiocontrol. The carbon?boron bond can be further functionalised by cross‐coupling allowing further functionality to be introduced after cycloaddition. |
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Keywords: | boranes cycloadditions pyridines regioselectivity triazines |
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