Silver-catalysed enantioselective addition of O-H and N-H bonds to allenes: a new model for stereoselectivity based on noncovalent interactions.

The ability of silver complexes to catalyse the enantioselective addition of O-H and N-H bonds to allenes is demonstrated for the first time by using optically active anionic ligands that were derived from oxophosphorus(V) acids as the sources of chirality. The intramolecular addition of acids, alcohols, and amines to allenes can be achieved with up to 73% ee. The exploitation of a C-H anomeric effect allowed the absolute configuration of a sample of 2-substituted tetrahydrofuran of low ee to be unambiguously assigned by comparison of the chiroptical ORD and VCD measurements with calculated spectra.

Unusual regiodivergence in metal-catalysed intramolecular cyclisation of gamma-allenols.

Different O-heterocycles can be obtained from a common gamma-allenol precursor by using Ag, Zn or Sn catalysts; the results were rationalised by molecular modelling.