EXCEPTIONALLY STABLE OZONIDES - INFLUENCE OF METHYL SUBSTITUENTS ON THE COURSE OF CYCLOPENTENE OZONOLYSES AND ON THE REACTIVITIES OF OZONIDES

Ozonolyses of 1,2,3,3,4,4,5,5-octamethyl- (1a), 1,2,3,3,4,4,5-heptamet hyl- (1b), and 1,2,3,3,4,4-hexamethyl cyclopentenes (1c) in methanol d id not yield the ordinary hemiperacetals but gave the corresponding oz onides 6a-c instead. The ozonides 6a,b were extremely stable nd remain ed intact even when refluxed with triphenylphosphine in tetrahydrofura n. Cycloreversion of the primary ozonides from unsymmetrically substit uted 1,2,3,3-tetramethylcyclopentene (1d) and 1,5,5-trimethylcyclopent ene (1g) was highly regioselective to yield the intermediate omega-oxo carbonyl oxides with the geminal methyl groups remote from the carbon yl oxide groups.