BECKMANN-Umlagerung und Fragmentierung; V. Teil Mechanismus der 7-Zentren-Fragmentierung von 1-Oxo-5-oximino-9-methyl-trans-decalin. Fragmentierungsreaktionen, 22. Mitteilung

The reaction rates of heterolytic fragmentation of 5-(p, -toluenesulfonyloxyimino)-1-oxo-9-methyl-trans-decalin ( 1 ), induced by sodium hydroxide in 80% ethanol and by sodium ethoxide in 100% ethanol, has been determined. The reaction of the oxime tosylate 1 with sodium ethoxide is first order with respect to both reactants. A similar base-dependence is observed in the reaction of the oxime tosylate 1 with sodium hydroxide. These results are explained in terms of an addition-fragmentation mechanism. This involves reversible addition of NaOH or NaOC₂H₅ to the carbonyl group of the oxime tosylate 1 and concerted fragmentation of the addition compounds 5a and 5b , yielding 9-cyano-6-methyl-trans-non-5-enoic acid ( 4a ) and the corresponding ethyl ester 4b , respectively. These reaction appear to be the first cases of concerted and stereospecific 7-centre fragmentation.