Cyclopentanoids from phenol. Part 4. 3-Substituted 4-hydroxycyclopent-2-enones

Abstract

Various 3-halogeno- and 3,5,5-trihalogeno-4-hydroxycyclopent-2-enone derivatives were prepared from 3,5,5-trichloro-4-hydroxycyclopent-2-enone (2), which is available in two steps from phenol via(1R*,4R*)-3,5,5-trichloro-1,4-dihydroxycyclopent-2-ene-1-carboxylic acid (1). Conjugate addition–elimination reactions of the 3-chloro-4-(dimethy-t-butylsilyloxy)-, the 3-chloro-4-tetrahydropyranyloxy-, and the 5,5-dichloro-3-iodo-4-tetrahydropyranyloxycyclopent-2-enones (20), (21), and (7), respectively, with lithium and magnesium cuprate reagents lead to synthetically useful 3-alkyl-4-hydroxycyclopent-2-enones in high yield.