Catalytic synthesis of nonracemic azaproline derivatives by cyclization of β-alkynyl hydrazines under kinetic resolution conditions

Article abstract of DOI:10.1002/anie.201101090

No metals required: Starting from readily accessible γ-silyl allenyl esters, β-alkynyl hydrazines were prepared in one step and subsequently cyclized in the presence of ammonium and phosphonium catalysts leading to dehydroazaproline products (see scheme;