Ylide compounds 1.4- hydrogen shift

The spirocyclic benzoxepines 50 (R = Ph, p-MeCgH4, t-butyl) were obtained unexpectedly by isomerisation of the vinyl carbonyl ylide intermediates obtained from reaction of indanetrione with vinyl diazo compounds, and subsequent eyelisation and a 1,5-hydrogen shift. 

Step, S-ylides 83 were probably formed, which then underwent a [2,3]-rearrangement to give allenic intermediates 84. Finally, the latter could have undergone a 1,3-hydrogen shift to yield compounds 85. 

The thermal acid-catalysed redox amination of carbonyl compounds by 3-pyrroline (150) to give Al-alkylpyrroles (151) has been reinvestigated computationally for the case of 2-phenylpropanal [i.e. =Ph(Me)CH, R = H]. Two previous 1,3-hydrogen shift mechanisms - either one-step or stepwise via free iminium ions - have been discounted. The formation of an azomethine ylide intermediate, assisted by acetic acid, is proposed. ... 

Etherification. The [Rh2(OAc)4]-catalyzed reaction of ph-thalimides and succiniinides with a-diazocarbonyl compounds provided a facile access to ( -alkylimidates in good 3delds (eq 50). No N-H insertion product was observed. The Rh-carbene species reacted at the oxygen atom of the imidic carbonyl group chemoselectively to produce a carbonyl ylide that reacted further by intramolecular hydrogen shift to furnish the observed imino ether. 

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