Bachollet SPJT, Vivat JF, Cocker DC, Adams H, Harrity JPA. Development of a mild and versatile directed cycloaddition approach to pyridines.
Chemistry 2014;
20:12889-93. [PMID:
25145488 PMCID:
PMC4313684 DOI:
10.1002/chem.201403916]
[Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Indexed: 11/14/2022]
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 carbonboron bond can be further functionalised by cross-coupling allowing further functionality to be introduced after cycloaddition.
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