Abstract:
The photochemical and acid-catalysed behaviour of a number of 4-hydroxy-4-alkylcyclohexa-2,5-dienones (para-quinols) has been investigated.
Peroxyacetic acid oxidation of some diterpenoid and steroid phenols and their methyl ethers gave para-quinols, in yields of up to 60%. On photolysis with a medium pressure mercury lamp, the dienones gave spirans (e.g. 133), presumably formed by 3-5 bond formation and collapse of the resulting cyclopruopanol. The spirans underwent further rearrangement to give butenolides (e.g. 135). In one steroidal dienone (159) a butenolide (164) was the only product isolated. Rational mechanisms for these transformations are advanced.