Hydrometallation allenes

Reductive coupling of 1,1-dimethylallene and 5-nitro-2-furancarboxaldehyde under a deuterium atmosphere provides the product of ferf-prenylation incorporating deuterium at the interior vinylic position (80% H). This result is consistent with a mechanism involving allene-aldehyde oxidative coupling. However, alternate pathways involving allene hydrometallation to furnish allyliridium species cannot be excluded on the basis of these data (Scheme 10). 

The ruthenium-catalyzed cycloisomerization of a variety of <5-enallenes was also achieved, forming cyclic 1,3-dienes or 1,4-dienes depending on the substrates and reaction conditions [32] (Eq. 22). This intramolecular coupling of the C=C bond and allenes can be envisioned by the initial hydrometallation of the allene moiety followed by intramolecular olefin insertion and isomerization. 

The RhI-catalysed rearrangement of A-allylaziridines to (Z)-A-alkenylaziridines has been investigated by computational methods and the reaction occurs via a hydrometalation//3-hydride elimination. Alkylidene cycloheptadienes have been prepared via a rhodium(I)-catalysed tandem isomerization of cyclopropylenynes through a [1,5] carbon-carbon migration via an allene intermediate with high Z E selectivities (Scheme 152). ... 

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