Oximino malonates, intramolecular

There are other Diels-Alder approaches to pyridines but they do not proceed in one step. For example, Weinreb reported the intramolecular Diels-Alder of oximino malonates tethered to a diene. Thermolysis of 102 produced 103 that upon treatment with base afforded pyridine 104. 

Methods for the synthesis of substituted pyridines remains an intense topic of research. One of the most popular approaches to substituted pyridines remains cycloaddition reactions. While this strategy is not new and many examples are in the current literature <00TL10251>, the state-of-the-art has been expanded. Weinreb and co-workers have reported the regioselective synthesis of pyridines (3) via intramolecular oximino malonate hetero Diels-Alder reactions (1 - 2) <00OL4007>. Similarly, the intramolecular [4 + 2] cycloaddition of... 

Intramolecular oximino malonate hetero-Die 1-Alder reactions give the regioselective synthesis of pyridines in a two-step process in modest to good yields (Scheme 61) <20000L4007>. 

Isoxazolo[2,3- ]pyridin-2-one derivatives such as 568 were prepared by intramolecular oximino malonate HDA reactions. These compounds underwent aromatization to substituted pyridines under mild basic conditions (Scheme 139) <20000L4007>. 

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