Ring cleavage double

Hydroxyoxaziridines like (117) undergo double ring cleavage to form, for example, a nine-membered keto lactam (81AG(E)670). 

While the oxidation of ketones by peracids (Baeyer-Villiger reaction) has been used in steroids mainly for ring cleavage, it has occasionally been applied to 20-ketopregnanes for conversion to 17-acetoxy- or hydroxyandros-tanes. The synthetic utility of this method is limited since reactive double bonds and other ketones are incompatible with the reagent. 

Based on the few reported examples, the pattern of ring cleavage that accompanies the ionic hydrogenation of alkylidenencyclopropanes seems to be related to the pattern and degree of substitution on both the ring and the double bond.233 Thus, treatment of l,l-dimethyl-2-methylenecyclopropane with two equivalents of triethylsilane and four equivalents of trifluoroacetic acid for 90 hours at room temperature yields 65% of 2,3-dimethylbutane (Eq. 114).229 Exposure of 1,1-dimethyl-2-isopropylidenecyclopropane to the same ratio of reactants at 50° for 16 hours produces a complex mixture containing 63% of 2,5-dimethylhexane, 18.5% of 2,5-dimethyl-3-hexene, 1.6% of 2,5-dimethyl-2-hexene, and 7% of 2,5-dimethyl-2-hexyl trifluoroacetate (Eq. 115).229... 

The behavior of both isomeric 1,4,2- and 1,3,4-oxathiazole derivatives, with an exocyclic double bond, towards nucleophiles is different from that of dioxazolone derivatives (79), in the sense that ring cleavage is usually followed by subsequent fragmentation of the ring (Scheme 8). 

Hydrogenation/Reduction/Reductive Ring Cleavage of the N-0 Bond, 6.2 Hydroxylation of the Ring Carbon-Carbon Double Bond/Oxidation, 6.3 Ozonolysis. 6.4 Epoxidation... 

Ozonolysis of a double bond leads first to a so-called primary ozonide 40 through 1,3-dipolar cycloaddition. Rearrangement of primary ozonide 40 with ring cleavage produces a carbonyl oxide 42 and a carbonyl compound 41, which then recyclize to secondary ozonide 43. The reaction terminates with a redox process involving... 

---