Ozone 1,3-dipolar cycloaddition with alkene

Ozone is a symmetrical bent molecule with a central positively charged oxygen atom and two terminal oxygen atoms that share a negative charge. It is a 1,3-dipole and does typical 1,3-dipolar cycloadditions with alkenes. 

Ozonolysis is widely used both in degradation work to locate the position of double bonds and in synthesis for the preparation of aldehydes, ketones, and carboxylic acids. Ozone is a 1,3-dipole and undergoes 1,3-dipolar cycloadditions with alkenes. 

Dipolar cycloadditions are another important family, with the impressive sequence of reactions involved when ozone reacts with an alkene as an example here. At -78°, ozone adds 1.3 (arrows) to give the molozonide 1.4. On warming, this undergoes a 1,3-dipolar cycloreversion (1.4 arrows),... 

The reaction of ozone with alkenes is one of the most useful 1,3-dipolar cycloadditions. Ozone undergoes [3 + 2] cycloaddition to the alkene to give a... 

Further cycloadditions include the 1,3-dipolar cycloadditions as well as the respective [2-i-l]-reactions. The latter have already been mentioned in the reaction of carbenes photochemically generated from diazirines (Section 6.5.2.4). Experimental examples for [3-i-2]-cycloadditions have not yet been reported. Still theoretical considerations gave rise to the assumption that such reactions with, for example, azides, diazomethane or other classical 1,3-dipoles should readily take place on the surface dimers. The calculations further revealed that the cleavage of nitrogen under formation of the respective azacyclopropane as known for normal alkenes should also take place for the [3-i-2]-adducts bound to diamond. For the reaction with ozone (Section 6.5.2.3) it has not yet been clarified whether or not an ozonide is initially formed by [3-i-2]-cycloaddition, only then to be transformed into the carbonyl compound. 

The reaction of ozone with alkenes is one of the most useful 1,3-dipolar cycloadditions. Ozone undergoes [3 -I- 2] cycloaddition to the alkene to give a 1,2,3-trioxolane, which immediately decomposes by a [3 -I- 2] retro-cycloaddition to give a carbonyl oxide and an aldehyde. When the ozonolysis is carried out in the presence of an alcohol, the alcohol adds to the carbonyl oxide to give a hydroperoxide acetal. In the absence of alcohol, though, the carbonyl oxide undergoes another [3 -b 2] cycloaddition with the aldehyde to give a 1,2,4-trioxolane. 

The cycloaddition can also be analyzed in terms of HOMO-LUMO interactions (see page 756), with the interaction of the LUMO of ozone and the HOMO of the alkene being dominant. For a discussion, see Kuczkowski, R. L. in Padwa, A., Ed. 1,3-Dipolar Cycloaddition Chemistry, Vol. 2 Wiley-Interscience New York, 1984 pp. 197-276. 

Mechanism of Ozonolysis (Criegee mechanism) The initial step of the reaction involves a 1,3-dipolar cycloaddition of ozone to the alkene leading to the formation of the primary ozonide (molozonide or 1,2,3-trioxolane), which decomposes to give a carbonyl oxide and a carbonyl compound. The carbonyl oxides are similar to ozone in being 1,3-dipolar compounds and undergo 1,3-dipolar cycloaddition to the carbonyl compound with the reverse regio-chemistry, leading to a relatively stable secondary ozonide (1,2,4-trioxolane) (Scheme 5.47). 

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