Intermolecular Allene Functionalization by Silver-Nitrene Catalysis

Under
silver catalysis conditions, using [Tp*,BrAg]2 as the catalyst precursor, allenes react with PhINTs
in the first example of efficient metal-mediated intermolecular nitrene
transfer to such substrates. The nature of the substituent at the
allene seems crucial for the reaction outcome since arylallenes are
converted into azetidine derivatives, whereas methylene aziridines
are the products resulting from alkylallenes. Mechanistic studies
allow proposing that azetidines are formed through unstable cyclopropylimine
intermediates, which further incorporate a second nitrene group, both
processes being silver-mediated. Methylene aziridines from alkylallenes
derive from catalytic nitrene addition to the allene double bonds.
Both routes have resulted to be productive for further synthetic transformations
affording aminocyclopropanes.