Rearrangement reactions reversible solution-phase

Finally, we note the reversible solution-phase rearrangement of a collection of 1,3,3-trialkylated derivatives of spiro[indoline-2,3 [3//]naphth[2,l-b][l,4]oxazines and the corresponding 2-[2-oxo-l-naphthylidenoiminomethylene]indolines for which the enthalpy of reaction is known38, but these studies unfortunately fail to provide us any useful thermochemical information, such as enthalpies of formation. 

Cyclopropanes have not been prepared by the reverse reaction. However, l-(l-alkynyl)-2-vi-nyloxiranes 3 undergo successive Cope rearrangements at 300-350 " C (gas phase flow system) to give 2-(l-alkynyl)cyclopropanecarbaldehydes 4 of exclusive or predominant cis configuration. The reaction can alternatively be conducted in solution in sealed Pyrex tubes at 100-160°C, but then 4 is often accompanied by considerable amounts of byproducts. 

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