Base catalyzed formation and ring cleavage of 2- acyl-4- alkoxycarbonyI- 4-cyano substituted cyclobexanoles

ABSTRACT

The reaction of 1, 3-diaryI-2-propen- 1 -ones [1 a, b] with ethyl cyanoacetate in absolute ethanol in the presence of a catalytic amount of KOH at 50-55°C afforded 3-aroyl-l-cyano-4-hydroxy-2,4, 6-triarylcyclohexanecarboxylates [2a,b]. Base-catalyzed ring cleavage of 2a,b in refluxing ethanolic KOH solution afforded the corresponding 3-aryl- 2-cyano-2-propenoic acid 4 along with 1 a, b. The structure of 2 was established through different spectroscopic techniques and confirmed via dehydration using thionyl chloride in refluxing pyridine afforded 3. However, reaction of la with ethyl cyanoacetate in refluxing ethanol in the presence of secondary amine [piperidine or morpholine] as a basic catalyst gave the open-chain Michael adduct 6. Treatment of the latter with ethanolic KOH solution yielded 1,5-pentanedione derivative 7. The relative configurations of 3b and 6 were determined through single crystal X-ray diffraction analysis: