Carbonyl anti-(α-Amino)allylation via Ruthenium Catalyzed Hydrogen Autotransfer: Use of an Acetylenic Pyrrole as an Allylmetal Pronucleophile

A single ruthenium complex catalyzes two discrete transformations resulting in the net conversion of an acetylenic pyrrole and alcohols to products of carbonyl anti-(α-amino)­allylation. An initial catalytic process enables isomerization of an alkyne to a kinetically more reactive allene. A second catalytic process promotes alcohol-to-allene hydrogen transfer to form an aldehyde-allylruthenium pair that engages in regio- and diastereoselective carbonyl addition. A related reductive coupling of aldehydes mediated by 2-propanol also is described. The present catalytic processes represent rare examples of the use of alkynes as nucleophilic allylmetal precursors.