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Table 3 Comparison of various metal-based catalytic ‘on-water’ C-S coupling reactions with the present system CuO@ARF

From: An efficient heterogeneous catalyst (CuO@ARF) for on-water C-S coupling reaction: an application to the synthesis of phenothiazine structural scaffold

Entry Catalytic system Applicability Remarks Reference
01 CuI (1 mol%) 1.5 eqv TBAB (1 eqv); base KOH (1.5 eqv); 80°C, 10 h With aryl iodide; bromo- and chloroarenes gave poor yields even using 5 mol% CuI Excess strong base, not recyclable; CuI is poorly soluble in water, TBAB is moisture sensitive. [27]
02 CuCl and 1,2-diamine as ligand (>2 eqv); 120°C overnight heating With iodo- and bromoarenes. No selectivity was examined Precious 1,2-diamines in >2, equivalents, long reaction time, recyclable using the recovered solution - catalyst was not separated. [28]
03 Bi2O3/Diamine ligand; (each 10 mol%); 1 eqv KOH at 100°C With aryl iodide Presence of a ligand, high loading of the metal catalyst, long reaction time; recyclable using the recovered solution - catalyst was not separated. [29]
04 CoCl2.6H2O/cationic 2,2′-bipyridyl system, 1 eqv KOH; excess zinc, 100°C With aryl halides (iodide, bromide, and chloride). Presence of cationic 2,2′-bipyridyl; excess Zn; long reaction time; recyclable using the recovered solution - catalyst was not separated. [30]
05 FeCl3.6H2O (10 mol%) - bipyridyl complexes (10 mol%) ; KOH (4 eqv); 100°C, 24 h With aryl iodide Excess base, long reaction time; recyclable using the recovered solution - catalyst was not separated. [31]
06 CuO@ARF; copper oxide (2.8 mol%); base K2CO3 (1.1 eqv); 100°C, 8 h With aryl iodide Mild base - nearly equivalent (1: 1.1); shorter reaction time; chemoselectivity between iodo and bromo has been utilized in the synthesis of medicinally important phenothiazine scaffold, easy separation of heterogeneous catalyst (by simple filtration of resin beads), recyclable for five runs without loss of activity; catalytic amount of SDS, ligand-free.