ABSTRACT
Catalyst-dependent metathesis reactions between 3-en-1-ynamides and nitrosoarenes are described. Particularly notable are the unprecedented 1,4-metathesis reactions catalyzed by Ag(I) or Zn(II) to give 2-propynimidamides and benzaldehyde derivatives. With 3-en-1-ynamides bearing a cycloalkenyl group, 1,4-oxoimination products were produced efficiently. We have developed metathesis/alkynation cascades for unsubstituted 2-propynimidamides and benzaldehyde species generated in situ, to manifest 1,4-hydroxyimination reactions of 3-en-1-ynes. Both 1,4-oxoiminations and 1,4-hydroxyiminations increase the molecular complexity of products.
Subject(s)
Alkynes/chemistry , Amides/chemical synthesis , Benzaldehydes/chemical synthesis , Nitroso Compounds/chemistry , Catalysis , Crystallography, X-Ray , Cycloaddition Reaction/methods , Magnetic Resonance Spectroscopy , Molecular Structure , Silver/chemistry , Zinc/chemistryABSTRACT
Catalytic 1,4-dioxo functionalizations of 3-en-1-ynes to (Z)- and (E)-2-en-1,4-dicarbonyl compounds are described. This regioselective difunctionalization was achieved in one-pot operation through initial alkyne hydration followed by in situ Selectfluor oxidation. The presence of pyridine alters the reaction chemoselectivity to give 4-hydroxy-2-en-1-carbonyl products instead. A cooperative action of pyridine and Zn(II) assists the hydrolysis of key oxonium intermediate.
ABSTRACT
Going for gold: The title reaction has been developed and demonstrates a wide substrate scope with respect to the 1,6-enynes and nitrones (see scheme; DCE = 1,2-dichloroethane, Tf = trifluoromethanesulfonyl). The results for the enantioselective versions are also presented.
