Promoting Catalytic C-Selective Sulfonylation of Cyclopropanols against Conventional O-Sulfonylation Using Readily Available Sulfonyl Chlorides

Against the backdrop of the well-known O-sulfonylation of cyclopropyl alcohols with sulfonyl chlorides, we examined the feasibility of conducting regioselective C-sulfonylation. By emulating an umpolung strategy-guided design, we report for the first time the Cu(II)-catalyzed β-sulfonylation of cyclopropanols by a mechanism that potentially involves an oxidative addition of a sulfonyl radical to a metal homoenolate. Unlike reported methods, this protocol allows a practical synthetic route to γ-keto sulfone building blocks from cyclopropanols by leveraging commercially available aryl- and alkyl-sulfonyl chlorides, common reagents in organic chemistry laboratories. Using operationally simple open-flask conditions, the preparative scope of starting materials was demonstrated using an array of aryl- and alkyl-substituted sulfonyl chlorides and cyclopropanols (43 examples, up to 96% yield).

Pd(II)-Catalyzed Oxidative Naphthylation of 2-Pyridone through N-H/C-H Activation Using Diarylacetylene as an Uncommon Arylating Agent

A Pd(II)-catalyzed straightforward oxidative naphthylation of unmasked 2-pyridone derivatives is described using a twofold internal alkyne as a coupling partner. The reaction proceeds through N-H/C-H activation to provide polyarylated N-naphthyl 2-pyridones. An unusual oxidative annulation at the arene C-H bond of the diarylalkyne leads to the formation of polyarylated N-naphthyl 2-pyridones, where the 2-pyridone-attached phenyl ring of the naphthyl ring is polyaryl-substituted. Mechanistic studies and DFT calculations suggest a plausible mechanism based on N-H/C-H activation. The N-naphthyl 2-pyridone derivatives were studied to explore encouraging photophysical properties.

Domino Decarboxylative Arylation and C-O Selective Bond Formation toward Chromeno[2,3-b]pyridine-2-one Skeletons

Practical Pd-catalyzed 2-pyridones were designed to achieve chromeno[2,3-b]pyridine-2-ones. The reaction proceeds through domino nucleophilic addition and decarboxylative arylation, respectively. This methodology offers a moderately efficient approach to construct the bioactive, fused-heterocyclic skeletons via selective C-O bond formation and decarboxylative arylation in a single step with high selectivity and good yields.

RhIII -Catalyzed C6-Selective Oxidative C-H/C-H Crosscoupling of 2-Pyridones with Thiophenes

A rhodium(III)-catalyzed C6-selective dehydrogenative cross-coupling of 2-pyridones with thiophenes was developed for the synthesis of 6-thiophenyl pyridin-2(1H)-one derivatives. In this reaction, the excellent site selectivity was controlled by the 2-pyridyl directing group on the nitrogen of the pyridone ring. Control experiments indicated that the N-pyridyl was essential for the transformation. To the best of our knowledge, this procedure is the first successful example of the direct C6 heteroarylation of 2-pyridones with electron-rich thiophene derivatives. 4-Pyridone was also used as substrate to generate the corresponding C2 heteroarylated product. Moreover, this pyridyl directing group was readily removable to generate the biheteroaryl structures with a free N-H group.