FeCl₃-Catalyzed Nucleophilic Substitution of Propargylic Acetates with Enoxysilanes

Abstract

An efficient FeCl3-catalyzed substitution reaction of propargylic acetates with enoxysilanes under mild conditions to afford corresponding gamma-alkynyl ketones has been developed. The substitution reaction is followed by a TsOH-catalyzed cyclization without purification of the gamma-alkynyl ketone intermediates, offering a straightforward synthetic route to tri- or tetrasubstituted furans.

Scope and advances in the catalytic propargylic substitution reaction

“…Subsequent cyclization by p-TsOH without purication of the g-alkynyl ketone intermediates resulted into tri-or tetra substituted furans 86 in high yield, Scheme 34. 67 The reaction proceeded smoothly without exclusion of moisture or air from the reaction mixture. Both electrondonating and electron-withdrawing aromatic substrates reacted smoothly with enoxysilane 84 affording the corresponding alkylated products in high yields.…”

Transition Metal-Mediated Synthesis of Monocyclic Aromatic Heterocycles

“…The same group also reported that this transformation could efficiently be catalyzed by Fe(III) 9 salts. 254 In addition, it was later demonstrated that the Cu(II)-catalyzed protocol does not require the use of the p -toluenesulfonic acid co-promoter. 250 …”

The Synthesis of Aromatic Heterocycles from Propargylic Compounds

“…In 2007, our group [7] reported a straightforward synthetic route to trisubstituted furans. This process first entails the nucleophilic substitution of propargylic acetates 10 with enoxysilanes 11 to form the g-alkynyl ketones 12 in the presence of a catalytic amount of FeCl 3 (Scheme 5).…”