Catalytic Transformations of 2-Pyridones by Rhodium-Mediated Carbene Transfer

Abstract

An enantioselective cyclopropanation reaction of Nsubstituted 2-pyridones with diazo compounds has been realized by using a chiral rhodium complex as the catalyst, and the corresponding chiral cyclopropanes could be formed in good yields with high enantioselectivities. Moreover, using acceptor−acceptor dimethyl 2-diazomalonate as the carbene precursor, a novel 1,4rearrangement of a Boc group from N to C has also been discovered under rhodium catalysis.

Visible-light enabled synthesis of cyclopropane-fused indolines via dearomatization of indoles

“…2 In this regard, cyclopropane-fused indolines exist as the key units in many biologically active alkaloids, such as lundurines A–D (Scheme 1a). 3 Typically, strategies for the construction of cyclopropane-fused indolines rely on cyclopropanation of indoles with diazo compounds, 4 cyclopropenes, 5 ene–yne ketones 6 or tosylhydrazones 7 catalyzed by transition-metal complexes or enabled by visible light (Scheme 1b). However, the employment of potentially toxic and explosive carbene precursors might limit their synthetic applications.…”

Branching out: redox strategies towards the synthesis of acyclic α-tertiary ethers

“…Recently, Sun reported the reaction of N -Boc pyridones with dimethyl 2-diazomalonate-derived carbenes (Scheme 103). 385 It was proposed that addition of the pyridone to the generated rhodium carbene could form an ylide intermediate, which could undergo a cyclisation onto the pendent carbamate. C–N cleavage in the resulting tetrahedral intermediate resulted in the formation of an α-tertiary pyridyl ether.…”

Copper-catalyzed dearomative 1,4-carboxylate rearrangement of 2-carbonateindoles

“…Later, using triazoles, pyridotriazoles and cyclopropenes as the carbene precursors, such types of dearomative rearrangements have been developed. 9 After that, we wanted to extend this rearrangement to heterocycles rather than 2-oxypyridines. Herein, we wish to report our endeavour to find a novel dearomative 1,4-rearrangement of indoles under copper catalysis.…”