Synthesis of Substituted Pyrroles via Copper‐Catalyzed Cyclization of Ethyl Allenoates with Activated Isocyanides

Abstract

A new method for the synthesis of di- and trisubstituted pyrroles via copper-catalyzed cyclization of ethyl allenoates with activated isocyanides has been developed. In contrast to related annulation reactions previously reported, this new process features a skeletal rearrangement in which the aryl sulfonyl moiety, which functions as the electron-withdrawing group in the α-carbon of the isocyanide, was found to migrate to the γ-carbon of the starting allenoate in the final product for the first time.

Recent Advances on Pyrrole Synthesis through Different Annulation Modes

“…Using ethyl allenoates and activated isocyanides as substrates, Yu and Lu et al [85] developed a copper-catalyzed cyclization reaction for the synthesis of substituted pyrroles (Scheme 53). During this process, an interesting elimination and re-addition of the EWG group was observed.…”

Recent Advances for the Synthesis of N‐Unsubstituted Pyrroles

“…Unlike the reactions of alenoates with aminocarbonyls, which are considered formal cycloaddition, the interaction of ethyl allenoates 262 with CH-activated isocyanides 263 results in pyrroles 264 with unusual migration of the alpha substituent isocyanide. [85] As shown in Scheme 88 authors was interested in the outcome of a similar process when an allenoate such as 262 a was employed as the electrophile in its reaction with an activated isocyanides. A characteristic feature of the reactions is the use of a dioxane/water mixture as a solvent system…”

TosMIC: A Powerful Synthon for Cyclization and Sulfonylation

“…All the synthesized derivatives were characterized using spectral analysis. [14] A plausible mechanism for the copper-catalyzed cyclization between allenoate and tosylmethyl isocyanide was proposed. The mechanism starts with a CÀ H bond activation by Cu 2 O catalyst to give a copper-isocyanide complex A with simultaneous formation of water.…”