Abstract Photocatalytic fluoroalkylative cyclization of alkenes provides an efficient approach to fluorinated heterocycles, yet existing methods generally require distinct radical precursors for different fluoroalkyl groups. Herein, we report a visible-light-induced ruthenium-catalyzed fluoroalkylative cyclization of o-alkenylbenzamides using readily available fluoroalkylsulfonyl chlorides as a unified family of radical precursors. This protocol enables the efficient synthesis of a broad range of fluoroalkylated iminoisobenzofurans bearing trifluoromethyl, difluoromethyl, and perfluoroalkyl substituents under mild conditions with a broad substrate scope and good functional group compatibility. Mechanistic studies support a photocatalytic radical pathway initiated by single-electron reduction of the fluoroalkylsulfonyl chlorides.
Abstract Succinimide-fused cyclobutenes are valuable building blocks for the synthesis of highly functionalized polycyclic structures. However, methods for constructing these structures—especially the N-aryl ones—remain limited. Herein, we provided an improved and rapid access to N-substituted succinimide-fused cyclobutenes by leveraging the copper-catalyzed Chan-Lam coupling. Desired products are afforded in 45–99% yields. Furthermore, this method features a broad substrate scope and good functional group compatibility.
Abstract A synthesis of 5,12,12-triaryl-5,12-dihydrobenzo[b]phenophosphazinium (DBPPZ+) was successfully developed via denitrogenative [4 + 2] benzannulation followed by a phospha-Friedel–Crafts cyclization. In the first step, phosphinyl ynamines reacted with phthalazine under single-electron oxidation conditions using tris(4-bromophenyl)ammoniumyl hexachloroantimonate (Magic Blue) or an acridinium photocatalyst to afford 2-amino-3-(phosphinyl)naphthalenes through [4 + 2] benzannulation and denitrogenative rearomatization. In the second step, treatment of the resulting 2-amino-3-(phosphinyl)naphthalenes with trifluoromethanesulfonic anhydride (Tf2O) induced an intramolecular phospha-Friedel–Crafts cyclization to furnish the desired DBPPZ+. Upon irradiation with UV light, DBPPZ+ exhibited strong fluorescence.
Abstract 4‑Nitro‑3,5‑bis(trinitromethyl)‑1H‑pyrazole (1) is an intriguing and highly substituted polynitro pyrazole featuring two symmetric trinitromethyl groups and a 4‑nitro‑functionalized pyrazole core, which poses a formidable challenge for its concise synthesis. Herein, we describe the development of two complementary synthetic strategies toward compound 1. The symmetric trinitromethyl moieties are efficiently installed via nucleophilic substitution followed by a two‑step nitration sequence, starting from commercially available 3,6‑dichloro‑1,2,4,5‑tetrazine (13). Initially, a Knorr pyrazole approach was developed starting from commercially available ethyl acetoacetate; although the pyrazole ring could be efficiently constructed using hydrazine acetate, this route suffers from a relatively long synthetic sequence and low overall yield. Alternatively, a [4 + 1] cycloaddition strategy was investigated, which delivered the 4‑aminopyrazole intermediate in a single step. Subsequent oxidation of the amino group, followed by a high‑yielding nitration, successfully generated the 4‑nitropyrazole scaffold and enabled the highly efficient synthesis of 1 in only 5 steps.
Abstract A general photocatalytic platform has been developed for the synthesis of sulfonyl-substituted heterocycles from alkenes/alkynes and alkyl sulfonyl chlorides by using indoles as catalysts. This platform relies on the radical cascade cyclization without metal and base involvement and can be carried out with water as the reaction solvent. Mechanistic studies have indicated that the in situ-generated indole oligomers are the photocatalysts for this reaction.
