2- pyridines reaction with electron-rich alkenes

Reaction of 2-[(benzotriazol-l-yl)alkylamino]pyridines 341 with open-chain electron-rich alkenes 342 in the presence of BF3-Et20 gave 4-substituted 1,2,3,4-tetrahydropyrido[l, 2-n]pyrimidinium tetrafluorobo-rates 343 (98S704). 

Photocycloaddition reactions of alkyl and aryl 2-thioxo-3//-benzoxazole-3-carboxylates 142 to alkenes afforded stable isolable spirocyclic aminothietanes 143 <02HCA2383> similar reactions with both electron-poor and electron-rich alkenes were also performed on 2-methyloxazolo[5,4-h]pyridine <02EJO4211>. 

The Diels-Alder reaction with inverse electron demand has been one of the most intensively studied reactions of 1,2,4-triazines. In this reaction 1,2,4-triazines behave as electron-deficient dienes and react with electron-rich dienophiles to give, generally, pyridines (see Houben-Weyl, Vol. E7b, p 471 ff). [4 + 2] Cycloadditions of 1,2,4-triazines have been observed with alkenes, alkynes, strained double bonds, electron-rich double and triple bonds, but in a few cases also with electron-deficient alkynes C—N double and triple bonds can also be used as dienophiles. In addition to intermolecular Diels-Alder reactions, intramolecular [4 + 2] cycloaddition reactions of 1,2,4-triazines have also been studied and used for the synthesis of condensed heterocyclic systems. A review on the intermolecular Diels-Alder reaction was published by Boger and Weinreb 14 Sauer published a review on his studies in 1992,381 and E. C. Taylor published a summary of his own work on intramolecular Diels-Alder reactions in 1988.382... 

A similar system was proposed by Marko based on CuCl, phenanthroline, di-tert-butyl azodicarboxylate (DBAD) and N-methylimidazole (NMI) as additives showing efficient oxidation of both primary and secondary alcohols to carbonyl compounds, with molecular oxygen or air as the oxidant releasing water as the sole by-product. The catal3dic system exhibits good tolerance of the presence of electron-rich alkenes, thioethers and pyridine moieties, which could be involved in other oxidation reactions but remain unaffected by the catalyst. In the case of... 

If pyrrole would do a similar thermodynamically controlled exo Diels-Alder reaction with a vinyl pyridine, a short route to the interesting analgesic epibatidine could be imagined, with just a simple reduction of the remaining alkene left to do. The reaction looks promising as the pyridine makes the dienophile electron-deficient and pyrrole is an electron-rich diene . 

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