Synthesis of Substituted Pyridines via Regiocontrolled [4 + 2] Cycloadditions of Oximinosulfonates was written by Renslo, Adam R.;Danheiser, Rick L.. And the article was included in Journal of Organic Chemistry in 1998.Quality Control of Methyl 3-methylpicolinate This article mentions the following:
Diels-Alder cycloadditions of 2,2-dimethyl-5-tosyloxyimino-1,3-dioxane-4,6-dione (I) with a variety of 1,3-dienes proceed with regiochem. opposite to that observed with conventional imino dienophiles, providing expeditious synthetic routes to substituted pyridines, tetrahydropyridines, and pyrrolines. I is prepared in one convenient synthetic operation from Meldrum’s acid and reacts with conjugated dienes at -78 °C in the presence of 2 equiv of dimethylaluminum chloride to afford [4 + 2] cycloadducts in good to excellent yield. Exposure of these cycloadducts to the action of NaOMe and N-chlorosuccinimide in methanol-THF at room temperature then produces substituted pyridines. The utility of this new two-step annulation protocol is demonstrated in total syntheses of the pyridine alkaloids fusaric acid and (S)-(+)-fusarinolic acid. Heating the [4 + 2] cycloadducts derived from I in a mixture of acetonitrile and pH 7 phosphate buffer induces an unusual Stieglitz-type rearrangement leading to the formation of interesting spirobicyclic pyrrolines. In the experiment, the researchers used many compounds, for example, Methyl 3-methylpicolinate (cas: 59718-84-2Quality Control of Methyl 3-methylpicolinate).
Methyl 3-methylpicolinate (cas: 59718-84-2) belongs to pyridine derivatives. The ring atoms in the pyridine molecule are sp2-hybridized. The nitrogen is involved in the π-bonding aromatic system using its unhybridized p orbital. The lone pair is in an sp2 orbital, projecting outward from the ring in the same plane as the σ bonds. Reduced pyridines, namely tetrahydropyridines, dihydropyridines and piperidines, are found in numerous natural and synthetic compounds. The synthesis and reactivity of these compounds have often been driven by the fact many of these compounds have interesting and unique pharmacological properties. Quality Control of Methyl 3-methylpicolinate