Cu(II)/citric acid grafted to chitosan by dendritic units of melamine as a novel and highly efficient heterogeneous catalyst for the synthesis of 2-aminobenzothiazole derivatives

Supramolecular Cu(ii) nanoparticles supported on a functionalized chitosan containing urea and thiourea bridges as a recoverable nanocatalyst for efficient synthesis of 1H-tetrazoles

“…12,13 Interestingly, the supramolecular and non-covalent supporting of the homogeneous catalytic species or anchoring of the functional groups on the inorganic or organic supports as well as their hybrid ones to form heterogeneous catalysts can overcome the encountered problems. 8,11,[14][15][16][17][18][19][20][21][22][23][24][25] Various organic or inorganic supports including synthetic polymers, natural polymers such as chitosan and cellulose, 3,4,10,[26][27][28] bentonite, 29,30 SiO 2 , 31,32 perlite, graphene oxide, 33,34 MOFs, etc. have been used for this purpose.…”

“…It's surface functional groups including NH 2 and OH, make it an appropriate support for the preparation of heterogeneous catalysts. [9][10][11]22,25,[39][40][41][42][43] Although heterogeneous catalysts usually demonstrate lower catalytic efficiency and selectivity in comparison with homogeneous ones due to their insolubility in the reaction medium, the formation of active catalytic species nanoparticles or the use of nanoscale assemblies of supports may overcome this challenge. [44][45][46][47][48] Indeed, nano-ordered heterogeneous catalytic systems can form a bridge between the gap of homogeneous and heterogeneous catalysts through combination of synergistic effects of both systems.…”