Cu-Mediated Sulfonyl Radical-Enabled 5-exo-trig Cyclization of Alkenyl Aldehydes: Access to Sulfonylmethyl 1H-Indenes

Synthesis of meta-Sulfonylpyridines via Copper(II)-Catalyzed Cascade Sulfonylation/Cyclization/Aromatization of Tertiary Enamides with Sulfonylhydrazides

A copper(II)-catalyzed radical cascade reaction of N-propargyl enamides with sulfonyl hydrazides was developed, which provided an unprecedented method for the direct synthesis of meta-sulfonylpyridines in high efficiency with good functional group compatibility and simple operation. Mechanistic studies indicated that this tandem process might be composed of the radical addition, intramolecular cyclization and oxidative aromatization.

Copper-Catalyzed Radical Cascade Cyclization of N-Substituted Indole-3-Aldehydes with Aryl Alkenes: Access to Pyrrolo[1,2-a]indole Scaffolds

Herein, we report a Cu-DTBP-catalyzed [3 + 2] cycloaddition reaction between 1-(2-oxo-2-phenylethyl)-1H-indole-3-aldehyde and arylalkene, using DMF as the solvent. Under relatively mild reaction conditions, a series of indole compounds were synthesized in moderate yields (up to 73%). This protocol features good functional group tolerance and high atom economy. In addition, we synthesized a total of 20 target compounds, providing a reliable and straightforward method to obtain structurally diverse pyrrolo[1,2-a]indole derivatives.

The [3 + 2] Cycloaddition Reaction of N-Substituted Pyrrole-2-carboxaldehydes with Arylalkenes under Copper Catalysis: Access to Dihydropyrrolizine Skeletons

Herein, we found that treating N-substituted pyrrole-2-carboxaldehydes with arylalkenes in DMF in N2 at 120 °C could afford pyrrolidine scaffolds with an up to 85% yield. This approach has several remarkable features, such as atom and step economy, readily accessible raw materials, and easy-to-operate manner, providing a simple and efficient method for constructing complicated bicyclic pyrroles. Additionally, we have successfully synthesized 28 target compounds, which further demonstrates its practicality and wide applicability.

KI-Catalyzed Allylic Sulfonation of α-Methylstyrene Derivatives with Sulfonylhydrazides via Electrochemistry

A direct allylic C-H bond activation of α-methylstyrene derivatives with sulfonylhydrazines for the synthesis of allylic sulfones has been developed under exogenous oxidant- and metal-catalyst-free electrochemical conditions. Using the transfer of electrons in the current instead of a stoichiometric chemical oxidant, a series of valuable allylic sulfones were accessed with a wide substrate scope and excellent regioselectivity via radical coupling.

A radical-radical cross-coupling reaction of xanthene with sulfonyl hydrazides: facile access to xanthen-9-sulfone derivatives

A straightforward strategy for direct incorporation of sulfonyl units into a xanthene moiety for accessing xanthen-9-sulfone derivatives in good to excellent yields has been established via metal-free radical-radical cross-coupling reaction of xanthenes and sulfonyl hydrazides. Using easily accessible starting materials, this methodology proceeds efficiently with a high degree of functional group compatibility and with a wide scope of both xanthenes and sulfonyl hydrazides under operationally simple reaction conditions. Mechanistic investigations revealed that sulfonyl radicals could be generated from sulfonyl hydrazides in the presence of TBHP under an oxygen atmosphere.

Transition-Metal-Free Radical-Triggered Hydrosulfonylation and Disulfonylation Reaction of Substituted Maleimides with Sulfonyl Hydrazides

A convenient and practical hydrosulfonylation and disulfonylation of substituted maleimides was realized using sulfonyl hydrazides as the sulfur reagent and tert-butyl hydroperoxide as the oxidant. The advantages of the reactions include mild and transition-metal-free reaction conditions, good functional group tolerance, and readily available starting materials. The radical species-induced pathway is also demonstrated by mechanistic studies.

Synthetic and mechanistic aspects of sulfonyl migrations

Sulfonyl migrations, frequently described as ‘unusual’ or ‘unexpected’, from the last 20 years, including 1,2-, 1,3-, 1,4-, 1,5-, 1,6- and 1,7-sulfonyl shifts, through either radical or polar processes, either inter- or intramolecularly are reviewed.

A practical copper-catalyzed approach to β-lactams via radical carboamination of alkenyl carbonyl compounds

Functionalized β-lactams are highly important motifs in synthetic chemistry. We report an efficient and novel approach to the synthesis of β-lactams via a copper(i)-catalyzed cascade process involving C(benzyl)-H radical abstraction, intermolecular alkene addition, and intramolecular amination reaction. Variously substituted alkenes were synthesized from vinylacetic acid, leading to the corresponding β-lactams in moderate to good yields. Preliminary studies indicate that the reaction undergoes a free radical mechanism via a Cu(i)/Cu(ii)/Cu(iii) catalytic cycle.

Quick construction of a C–N bond from arylsulfonyl hydrazides and Csp2–X compounds promoted by DMAP at room temperature

A mild C–N coupling reaction with arylsulfonyl hydrazides and 2(5H)-furanones shows good yields, excellent reaction regioselectivity and functional group tolerance.

mCPBA-Mediated Intramolecular Oxidative Annulation of ortho-Crotyl or Cinnamyl Arylaldehydes: Synthesis of Benzofused Five-, Six-, and Seven-Membered Oxacycles

mCPBA-mediated intramolecular oxidative annulation of ortho-crotyl or cinnamyl arylaldehydes provides chroman, coumaran, isochroman, and tetrahydrobenzo[ c]oxepine under different reaction conditions. This research investigates the reaction conditions for facile and efficient transformation.