A review of the literature concerning reactions of ozone with amines has given rise to the working hypothesis that these reactions all involve initially the electrophilic attack of ozone to give an adduct for which at least three different reaction routes are available: loss of molecular oxygen to give an amine oxide or further reaction products thereof, an intramolecular oxidation of a side chain, and dissociation to nitrogen cation radicals and the ozonate anion radical, followed by further reactions of these. Results from ozonations of tert-butylamine and tri-n-butylamine, which furnish additional evidence for the above competitions, are described.>Tphe literature suggests several ways in which ozone reacts with amines.
Formation of tanacetophorone (IV) from a-thujadicarboxylic ester (I) involves alkoxide-catalysed cyclopropane cleavage to an olefinic ester followed by Dieckmann reaction (Path B), rather than Dieckmann reaction followed by retro-Michael reaction (Path A), since the intermediate keto-ester is (VI) and not (111). The retro-Michael reaction giving p-thujadicarboxylic ester (V) from the oc-ester (I) is largely complete before the Dieckmann cyclisation is very far advanced. Related examples are considered.TREATMENT of a-thujadicarboxylic ester (I) with sodium methoxide in methanol, followed by steam-distillation from acid solution, is the classical preparation of tanacetophorone (IV) .I* 2 It has been suggested3 that Dieckmann cyclisation of a-thujadicarboxylic ester gives the keto-ester (11, shown as anion) which by retro-Michael reaction followed by hydrolysis and decarboxylation yields tanacetophorone (Path A). This mechanism has been cited,4,5 though with reservations.? Recent work61 7 on the base-catalysed cyclopropane * The conclusions reached were presented a t the XIXth International Congress of Pure and Applied t P.
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