Reaction of Derivatives of the [2+2]-Cycloadduct of Dichloroketene and Dimethylfulvene with Ozone

Previously unknown optically active cyclopentenones were synthesized by the ozonation of 2-dichloromethyl-5-(1-methylethylidene)-N-[(1R)-1-phenylethyl]cyclopent-3-ene-1-carboxamide in CH₂Cl₂–MeOH (10 : 1) at 0°C and of (3aR,6aR)-3-hydroxy-6-(1-methylethylidene)-2-[(1R)-1-phenylethyl)-3,3a,6,6a-tetrahydrocyclopenta[c]pyrrol-1(2H)-one in cyclohexane–MeOH (10 : 1) at 5°C until complete consumption of the starting compounds (by TLC), followed by treatment with Me₂S. The new obtained cyclopentenons: 2-(dichloromethyl)-5-oxo-N-[(1R)-1-phenylethyl]cyclopent-3-ene-1-carboxamide and (3aR,6aR)-3-hydroxy-2-[(1R)-1-phenylethyl]-2,3,3a,6a-tetrahydrocyclopenta[c]pyrrole-1,6-dione are useful compounds to prepare cyclopentanoids.