Transition-Metal-, Additive-, and Solvent-Free [3 + 3] Annulation of RCF₂-Imidoyl Sulfoxonium Ylides with Cyclopropenones to Give Multifunctionalized CF₃-Pyridones

Abstract

An efficient and practical strategy was developed to synthesize 1,3,4-triaryl-6-trifluoromethylpyridones from CF3-imidoyl sulfoxonium ylides and cyclopropenones in good to excellent yields. This stepwise [3 + 3] annulation reaction was carried out under transition-metal-, additive-, and solvent-free conditions, generating 1 equiv of dimethyl sulfoxide as byproduct and tolerating a series of functional groups.

Ruthenium-Catalyzed Hydroxyl-Directed peri-Selective C–H Activation and Annulation of 1-Naphthols with CF3–Imidoyl Sulfoxonium Ylides for the Synthesis of 2-(Trifluoromethyl)-2,3-dihydrobenzo[de]chromen-2-amines

“…We commenced our study using 1-naphthol 1a and TFISY 2b as model substrates to optimize the reaction conditions (Table ). Notably, TFISYs could be readily synthesized by simply mixing trifluoroacetimidoyl chlorides with dimethylsulfoxonium methylide . To our delight, the reaction proceeded smoothly with [Ru­( p -cymene)­Cl 2 ] 2 as a catalyst and NaOAc as a base in DCE at 100 °C for 16 h, successfully affording the desired dihydrobenzo­[ de ]­chromen-2-amine product 3b in a 56% yield (Table , entry 1).…”

“…Recently, Cheng and co-workers used TFISYs as coupling partners in cascade cyclization reactions with 1,3dicarbonyl compounds or cyclopropenones, producing trifluoromethyl-substituted pyrroles or pyridines in good yields. 12 They also demonstrated a ruthenium-catalyzed C−H activation/annulation of benzoic acids and TFISYs for the synthesis of 3-(trifluoromethyl)isoquinolinones. 13 Prompted by the above pioneering work about TFISYs and our ongoing work on the efficient synthesis of trifluoromethyl-containing heterocycles using trifluoromethyl synthons, 14 we herein present a ruthenium-catalyzed hydroxyl-directed peri-selective C−H activation and cascade annulation reaction of 1-naphthols with TFISYs, which provides facile access to 2-(trifluoromethyl)-2,3-dihydrobenzo[de]chromen-2-amines with high efficiency.…”

“…Notably, TFISYs could be readily synthesized by simply mixing trifluoroacetimidoyl chlorides 15 with dimethylsulfoxonium methylide. 12 To our delight, the reaction proceeded smoothly with [Ru(p-cymene)Cl 2 ] 2 as a catalyst and NaOAc as a base in DCE at 100 °C for 16 h, successfully affording the desired dihydrobenzo[de]chromen-2-amine product 3b in a 56% yield (Table 1, entry 1). Other transition-metal catalysts commonly used in directed C−H functionalizations, such as [Cp*RhCl 2 ] 2 , [Cp*IrCl 2 ] 2 , and Cp*Co(CO)I 2 , were tested in this transformation, but only [Cp*RhCl 2 ] 2 could enable the production of 3b in a 18% yield (Table 1, entries 2−4, respectively).…”

“…CF 3 -substituted imidoyl sulfoxonium ylides (TFISYs), a kind of versatile trifluoromethyl synthon, exhibited high reactivities in the formation of trifluoromethyl-containing compounds but gained only limited attention. Recently, Cheng and co-workers used TFISYs as coupling partners in cascade cyclization reactions with 1,3-dicarbonyl compounds or cyclopropenones, producing trifluoromethyl-substituted pyrroles or pyridines in good yields . They also demonstrated a ruthenium-catalyzed C–H activation/annulation of benzoic acids and TFISYs for the synthesis of 3-(trifluoromethyl)­isoquinolinones .…”

Unexpected Copper-Catalyzed Cascade Reaction of 1,6-Enynes with Sulfoxonium Ylides

“…Sulfoxonium ylides, as alternative carbene precursors to diazo compounds under metal catalysis, have made distinct achievements for hetero/carbocycle synthesis due to their advantages of operational safety, synthetic convenience, and diverse reactivity . However, two major challenges still exist to improve the versatility of these ylides in metal catalysis: the requirement for noble-metal catalysts and the limited reaction patterns in contrast to diazo metal–carbene conversions.…”