Ag^I‐Catalyzed Reaction of Enol Diazoacetates and Imino Ethers: Synthesis of Highly Functionalized Pyrroles

Abstract

An unprecedented Ag I -catalyzed efficient method for the coupling of imino ethers and enol diazoacetates through a[3+ +2]-cycloaddition/CÀObond cleavage/[1,5]-proton transfer cascade process is reported. The general class of imino ethers that includes oxazolines,b enzoxazoles and benzimidates are applicable substrates for these reactions that provide direct access to fully substituted pyrroles with uniformly high chemo-and regioselectivity.H igh variability in substitution at the pyrrole 2-, 5-and N-positions characterizes this methodology that also presents an entry point for further pyrrole diversification via facile modification of resulting N-functional pyrroles.

AgI‐Catalyzed Reaction of Enol Diazoacetates and Imino Ethers: Synthesis of Highly Functionalized Pyrroles

“…The structure of product 3ag was confirmed by single-crystal Xray diffraction analysis (Figure 2). [20] To demonstrate the practicality and synthetic utility of the current methodology,agram-scale reaction was conducted with oxazoline 1f,a ffording 3fa in 86 %i solated yield (Scheme 6, 4.0 mmol scale,1 .39 g). Subsequent transformations with 3fawere conducted.…”

Ruthenium‐Catalyzed Decarboxylative Rearrangement of 4‐Alkenyl‐isoxazol‐5‐ones to Pyrrole Derivatives

“…To avoid approaches based on the use of strong operating conditions, which are incompatible with many functional groups and a wide scope of the reaction, transition metal‐promoted synthetic protocols have been developed to access pyrroles under mild reaction conditions [4] . In this context, more recently Doyle and co‐workers described a silver‐catalyzed coupling reaction between enol diazoacetates and imino ethers providing fully substituted pyrroles at room temperature (Scheme 1, reaction 1) [5] . A copper‐catalyzed process through [3+2] spiroannulation of oximes and azadienes followed by aromatization of the first‐obtained 3 H ‐pyrroles was reported by the Jiang and Wei group (Scheme 1, reaction 2) [6] .…”

“…[4] In this context, more recently Doyle and coworkers described a silver-catalyzed coupling reaction between enol diazoacetates and imino ethers providing fully substituted pyrroles at room temperature (Scheme 1, reaction 1). [5] A copper-catalyzed process through [3 + 2] spiroannulation of oximes and azadienes followed by aromatization of the firstobtained 3H-pyrroles was reported by the Jiang and Wei group (Scheme 1, reaction 2). [6] Huang and co-workers developed a gold-catalyzed cycloisomerization of 1,5-diynes to afford 1,2,4trisubstituted pyrroles (Scheme 1, reaction 3).…”

Protecting Group-Dependent Synthesis of Densely Substituted Dihydropyrroles v/s Pyrroles via 5-Exo-trig Cascade Radical Cyclization to Alkynyl Vinylogous Carbamates

“…The classical methods for preparation of pyrroles are the Knorr, Hantzsch, and Paal–Knorr condensation . In the recent past, synthesis of pyrrole has been reported using multicomponent reactions and transition-metal catalyzed reactions . Similarly, 1,3-dipolar cycloaddition has emerged as one of the most useful reactions for the synthesis of 2,5-dihydropyrrole .…”