Ytterbium-Catalyzed Intramolecular [3 + 2] Cycloaddition based on Furan Dearomatization to Construct Fused Triazoles

Abstract

The 1,2,3-triazole-containing polycyclic architecture widely exists in a broad spectrum of synthetic bioactive molecules, and the development of expeditious methods to synthesize these skeletons remains a challenging task. In this work, the catalytic cyclization of biomass-derived 2-furylcarbinols with an azide to form fused triazoles is described. This approach takes advantage of a single catalyst Yb(OTf) 3 and operates via a furfuryl-cationinduced intramolecular [3 + 2] cycloaddition/furan ring-opening cascade.

HFIP in Organic Synthesis

“…The Yu group extended their furfuryl cation-induced [3 + 2] cycloaddition strategy to the synthesis of fused triazoles using Yb­(OTf) 3 (Scheme ). Several triflate-based Lewis acids were evaluated in DCM and provided high yield of the E -enone product; interestingly, the same Lewis acids in HFIP provided the Z -enone with no observed amounts of the E -enone. Yb­(OTf) 3 provided the highest yields in both solvents.…”

Dual Roles of Azide: Dearomative Dimerization of Furfuryl Azides

“…It has been demonstrated with DFT calculations that the strong hydrogen bonding donor HFIP plays a significant role in stabilizing the azaoxyallyl or oxyallyl cations . The merit of HFIP has been revealed in intramolecular [3 + 2] cycloaddition of furfuryl alcohols with organic azides . Sc­(OTf) 3 was identified as a superior catalyst in HFIP, giving the desired furfuryl triazole in 78% yield (entry 7).…”

“…19c The merit of HFIP has been revealed in intramolecular [3 + 2] cycloaddition of furfuryl alcohols with organic azides. 20 Sc(OTf) 3 was identified as a superior catalyst in HFIP, giving the desired furfuryl triazole in 78% yield (entry 7). And the yield was slightly reduced when the catalyst loading was decreased to 5 mol % (entry 8).…”

The construction of phosphonate triazolyl by copper(ii)-catalyzed furan dearomatized [3 + 2] cycloaddition

“…[39][40][41][42][43] Recently, our group developed a method to synthesize complementary triazoles directly from easily available furan derivatives (Scheme 1b). [44][45][46][47][48] This method involves an intermolecular [3 + 2] cycloaddition reaction between 2-furan carbinol and organic azide to produce triazole, followed by furan ring opening to form enone. Despite this method having been well established, these reactions still have some limitations, such as the use of stoichiometric amounts of strong Lewis acids (such as TiCl 4 or SnCl 4 ), which carry major handling and workup issues.…”