A Study of the Competition between the Di-.pi.-methane and the Azadi-.pi.-methane Processes in 2-Vinyl-.beta.,.gamma.-unsaturated Oxime Derivatives. The Novel Azadi-.pi.-methane Reactivity of .beta.,.gamma.-Unsaturated Oximes

Synthetic Aspects of the Di-π-methane Rearrangement

“…The results obtained showed that, while oxime 202a undergoes both reactions, oxime 202b yields the ADPM product exclusively. In another study aimed at detecting intramolecular competition between the all-carbon di-π-methane (DPM) rearrangement and the ADPM process, acetophenone-sensitized irradiation of oxime acetate 256a affords the cyclopropane 257a , resulting from the DPM process, in 84% yield . Similar DPM rearrangement was observed for the corresponding oxime trifluoroacetate 256b that gives the nitrile 258 , in 90% yield.…”

“…Literature precedents indicated that β,γ-unsaturated oximes were unreactive in the ADPM mode. , However, recent results have shown that these compounds can undergo the rearrangement with high chemical efficiency. This situation is observed in cases in which the biradical intermediates are highly stabilized as in compounds 239 , 240 , and 241 that afford the corresponding ADPM product 242 , 243 and 244 respectively, on acetophenone-sensitized irradiation. ,

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“…However, oxime trifluoroacetate 259 undergoes the ADPM rearrangement exclusively affording cyclopropane 260 , in 30% yield, again resulting from thermal elimination of trifluoroacetic acid. The selectivity observed for compounds 256 and 259 is interpreted as being dependent on the relative stabilities of the corresponding 1,4-bridged biradical intermediates …”

5.06 Di-π-methane, Oxa-di-π-methane, and Aza-di-π-methane Photoisomerization

“…Various examples of nitrile formation in the context of the aza-di-p-methane photoisomerization of oxime derivatives have been published. 98 The same reaction conditions with acetophenone as triplet sensitizer were applied to the transformation of the ketoxime 161 into the rearranged product 162. 98 It should further be pointed out that the hydroxyl function of the ketoxime group did not need to be acylated.…”

“…98 The same reaction conditions with acetophenone as triplet sensitizer were applied to the transformation of the ketoxime 161 into the rearranged product 162. 98 It should further be pointed out that the hydroxyl function of the ketoxime group did not need to be acylated. In this case, the reactivity is increased by the conformational rigidity of the substrate.…”