Kondrat’eva吡啶合成反应

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on style="text-indent: 2em;">恶唑（氮杂二烯）和亲二烯体通过反电子要求型的杂-Diels–Alder反应，开环，芳构化制备吡啶衍生物的{attr}3183{/attr}。此反应由Kondrat’eva在1957年首次报道【Kondrat’eva, G. Ya., Khim. Nauk. Prom., 1957, 2, 666】。

此反应一个的应用是合成Vitamin B6, 5-乙氧基-4-甲基恶唑和马来酸酐进行环加成，水解，还原得到产物。

【Tetrahedron 1967,23, 943-955 】

反应机理

机理和Boger吡啶合成反应类似，恶唑（氮杂二烯）和亲二烯体进行反电子要求型的Hetero-Diels–Alder reaction（杂-Diels–Alder反应）得到双环中间体，开环，消除芳构化，得到吡啶类化合物。

反应实例

A solution containing 0.1 g N-(4-methyloxazol-2-yl)-N-(pent-4-enyl)acetamide(0.5 mmol) and 0.06 g DBU (0.4 mmol) in 2 mL toluene in a sealed tube under an argonatmosphere was heated at 180◦C for 20 h. Then the solvent was removed under reducedpressure, and the residue was purifified by flflash silica gel chromatography to give 0.3 g1-acetyl-7-methyl-1,2,3,4-tetrahydro-1,8-naphthyridine as a pale yellow oil, in a yield of39%. (Note: It requires 0.842 g starting material to afford 39% naphthyridine derivative ina yield of 39%, but it was stated as 0.1 g in the original article.)

【J. Org. Chem., 1999, 64, 3595.】

A solution of 0.15 g oxazole alc ohol (0.41 mmol) and 0.05 g DBN (0.41 mmol) in 60 mLanhydrous o-dichlorobenzene was deoxygenated with argon for 45 min. The mixture washeated at 150◦C under an argon atmosphere for 1.5 h and then cooled to room temperature.Upon removal of solvent in vacuo, the residue was purifified by flflash chromatography usingMeOH/EtOAc (1:49) as the eluent to afford 0.10 g pyridine alcohol as a pale yellow oil, ina yield of 71%.

【J. Org. Chem., 1989, 54, 5580】