Enantioselective Palladium(II) Phosphate Catalyzed Three‐Component Reactions of Pyrrole, Diazoesters, and Imines

Abstract

Reaction trio: The title reaction delivers CH functionalized pyrrole derivatives in moderate to good yields. This novel three‐component reaction provides both syn‐ and anti‐pyrrole derivatives having two contiguous stereocenters with good regio‐, diastereo‐, and enantioselectivity. This process represents the first highly enantioselective palladium‐carbenoid‐mediated reaction.

Asymmetric Multicomponent Reactions Based on Trapping of Active Intermediates

“…After successful trapping of zwitterionic intermediates derived from diazo compounds and indoles with imines, we wished to extend this novel trapping process to include pyrrole 30 , and envisioned the trapping of proposed zwitterionic intermediates V derived from pyrrole and diazo compounds by use of imines (Scheme ) . When the reaction of a diazo compound, unprotected pyrrole 30 and an imine was conducted under the catalysis of rhodium and PPA, the rhodium catalyst was poisoned, thus leading to slow diazo decomposition.…”

Pd(ii)-catalyzed formal [4+1] cycloaddition reactions of diazoacetates and aryl propargyl alcohols to form 2,5-dihydrofurans

“…2 They have also drawn growing attention in carbenoid chemistry such as cross-coupling reactions 3 , X-H insertions 4 and ylide-trapping processes. 5 Transition metal-catalyzed reactions of diazo compounds and propargyl alcohols or homopropargyl alcohols have been studied by several groups (Scheme 1). Wood and co-workers reported that diazoketones and propargyl alcohols underwent [2,3]-or [3,3]-sigmatropic rearrangement depending on the Rh(II) catalyst of choice.…”

Enantioselective Palladium‐Catalyzed Insertion of α‐Aryl‐α‐diazoacetates into the OH Bonds of Phenols

“…The early examples of palladium-catalyzed asymmetric carbene-transfer reactions involved cyclopropanations and carbenylative amination, however, the resulting enantioselectivity was unsatisfactory. [4] Recently, Hu and co-workers [5] reported highly enantioselective palladium-catalyzed three-component reactions of pyrrole, diazoesters, and imines. Herein, we report a palladiumcatalyzed asymmetric insertion of a-aryl-a-diazoacetates into the O À H bond of phenols (Scheme 1).…”