Transition-metal-free synthesis of chalcogenated furans through the sequential thiol-Michael/Paal–Knorr reaction of 1,4-enediones in the presence of a catalytic amount of p-toluene sulfonic acid has been developed.
A three-component strategy for the synthesis of 4-thioarylpyrroles from 1,4-enediones, thiols, and ammonium formate in one-pot has been developed. The reaction proceeds through the sequential thiol-Michael/Paal–Knorr reaction of 1,4-enediones with the formation of one new C–S and two C–N bonds. The operationally simple protocol provides direct access to the highly functionalized 4-thioarylpyrroles with free-NH in good to excellent yields. The synthetic application of resulting 4-thioarylpyrroles was demonstrated by oxidation of the sulfur atom to the corresponding sulfoxide and sulfone.
This paper describes the synthesis of multisubstituted furans through tricyclohexylphophine mediated intramolecular annulation of 1, 4‐enediones under solvent‐free greener reaction conditions. The reaction proceeds via nucleophilic attack of P(Cy)3 on the β‐carbon of 1, 4‐enediones to form oxaphosphetanes with new C–O bond formation which further eliminates O=P(Cy)3 to afford furans. The present methodology is compatible with a wide range of substrates and enabled the synthesis of a broad range of biologically significant furan derivatives in good to excellent yields (55–93%).
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