1,3-Dicarbonyl (e.g. beta-ketoester) | if no other reagents are used and we work in a basic medium, we will obtain alpha-pyrone by condensation (the Section called Pechmann synthesis of Aplha-Pyron) |
| imin formation (Retro Step: r1a) The imin will be formated only on the reactive keto group, because the carbonyl-carbon atom of the ester is less electrophil caused by the +M effect of the alkoxy group.
|
| imin-enamin-tautomerism, the enamin is more stable, because the formated conjugated system. Attack of the enamin under michael-addition (the Section called Michael-Addition in Chapter 7) nucleophilic attack to vinyl-like carbon-carbon double bond (Retro Step: r2)
|
|
|
1,4-Dihydropyridin |
|
| |