Borderline metal catalysts, Bi(OTf)3 and Fe(OTf)3, were proven to work as dual activators for alkynes and N,O-acetals via σ,π-chelation, which achieved a new carboarylation reaction of alkynylarenes with N,O-acetals.
Lewis acid catalyzed cascade annulation of alkynols with α-ketoesters: a facile access to γ-spiroketal-γ-lactones
作者:Digambar A. Kambale、Sagar S. Thorat、Madhukar S. Pratapure、Rajesh G. Gonnade、Ravindar Kontham
DOI:10.1039/c7cc03668j
日期:——
A novel Lewisacidcatalyzed intermolecular cascade annulation of alkynols with α-ketoesters has been developed. This simple and efficient cascade annulation proceeds through a 5-exo-dig cyclization of alkynols followed by annulation with α-ketoester to provide a wide variety of unsaturated γ-spiroketal-γ-lactones (1,6-dioxaspiro[4.4]non-3-en-2-ones) related to many natural products.
spirocyclic pyrazolidines in a one-pot process was developed. The gold-catalyzed three-component coupling of alkynols, hydrazines and aldehydes or ketones likely proceeds via cycloisomerization of the alkynol to an exocyclic enol ether and subsequent [3 + 2]-cycloaddition of an azomethine ylide. A library of 29 derivatives with a wide range of functional groups was synthesized in up to 97% yield. With this new
Asymmetricallylic alkylation (AAA) is a powerful method for the formation of highly useful, non-racemic allylic compounds. Here we present a complementary enantioselective process that generates allylic lactones via π-acid catalysis. More specifically, a catalytic enantioselective dehydrative lactonization of allylicalcohols using a novel PdII-catalyst containing the imidazole-based P,N-ligand (S)-StackPhos
Bismuth(<scp>iii</scp>)-catalyzed cycloisomerization and (hetero)arylation of alkynols: simple access to 2-(hetero)aryl tetrahydrofurans and tetrahydropyrans
作者:Ashwini K. Nakate、Madhukar S. Pratapure、Ravindar Kontham
DOI:10.1039/c8ob00368h
日期:——
2-(Hetero)aryl tetrahydrofurans and tetrahydropyrans were successfully synthesized using Bi(OTf)3-catalyzed hydroalkoxylation (cycloisomerization) of alkynols (via 5 or 6 exo-dig cyclization) and intermolecular (hetero)arylation. This reaction involves a highly efficient cascade process, where initially the alkynol undergoes a cycloisomerization step via activation of the triple bond and generates