关键词: 钴氟络合物, 酰氟, 磺酰氟, 氟化, 氟氯交换

Acyl fluorides are valuable intermediates in organic synthesis and have found broad applications in medicinal chemistry and functional materials. However, established synthetic methods often rely on unstable or hazardous fluorinating reagents, harsh reaction conditions, or expensive catalysts, thereby limiting their practical utility. Herein, we report an air-compatible fluorination of acyl chlorides and sulfonyl chlorides catalyzed by the cobalt fluoride complex [CoF₃(terpy)]·MeOH·H₂O (terpy = 2,2′:6′,2″-terpyridine), with inexpensive and readily available potassium fluoride (KF) serving as the terminal fluoride source. In a typical procedure, an oven-dried Schlenk tube equipped with a magnetic stir bar was charged with an acyl chloride or sulfonyl chloride (0.20 mmol), [CoF₃(terpy)]·MeOH·H₂O (0.010 mmol, 5.0 mol%), KF (0.40 mmol, 2.0 equiv.), and acetonitrile (2.0 mL). The mixture was stirred in air at 25 °C for 10 h. After completion of the reaction, the mixture was concentrated under reduced pressure, and the residue was purified by silica gel column chromatography. Under the optimized conditions, benzoyl chloride was converted to benzoyl fluoride in 99% yield. Moreover, the catalytic system exhibited good reactivity and functional-group tolerance toward electronically and structurally diverse acyl and sulfonyl chlorides. Notably, it enabled the preparation of functional products, including a coumarin-derived fragrance and the fluorescent inhibitor dansyl fluoride. A gram-scale reaction conducted on a 5.0 mmol scale afforded 1.21 g of the target sulfonyl fluoride in 96% yield, demonstrating the preparative utility of the method. Density functional theory calculations indicated that fluoride transfer from the axial Co-F bond is kinetically favored over transfer from the equatorial Co-F bond, with calculated activation free energies of 23.2 and 26.9 kcal·mol⁻¹, respectively. Mulliken charge analysis further suggested that the axial fluoride ligand has greater nucleophilic character. Collectively, these results support a plausible catalytic pathway involving fluoride transfer from the axial Co-F bond to the carbonyl carbon of the acyl chloride, followed by regeneration of the cobalt fluoride catalyst by KF. Overall, this protocol features mild reaction conditions, operational simplicity, broad substrate scope, and good functional-group tolerance, providing a practical and economical route to acyl fluorides and sulfonyl fluorides.

Key words: cobalt fluoride complex, acyl fluoride, sulfonyl fluoride, fluorination, fluorine-chlorine exchange