Cycloreversion intermediate oxetane

Treatment of 3/9,17/S-diacetoxy-5,10-secoandrost-l(10)-en-5-one (164) with BF3. Et20 has been shown to proceed with cleavage of the macrocycle and formation of a new compound (165) containing a cyclopentene ring.140 Based on DFT calculations, a possible mechanism has been proposed involving an intramolecular Lewis acid promoted 2 + 2-cycloaddition, followed by a cycloreversion of the intermediate oxetane (Scheme 45). 

Synthesis of ( )-non-6-en-l-ol (315), the sex attractant of the Mediterranean fruit fly (Ceratitus capitata) was achieved by Jones et al. 150) through photochemical addition of propanal and 1,3-cyclohexadiene (311) and subsequent thermal cycloreversion of the bicyclic oxetane intermediate (313) (Scheme 57). The critical cycloreversion step was >95% stereoselective. This synthesis is significantly shorter than that reported by Jacobson et al. 151). Rossi 152) has also reported a convenient synthesis. 

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