Guanidinium-based sulfonic acid as a new Brønsted acid organocatalyst in organic synthesis in water

Abstract

Guanidinium-based sulfonic acid as a new Brønsted acid organocatalyst has been synthesized, characterized, and applied for the synthesis of 3,4-dihydroquinoxalin-2-amine, 1,6-dihydropyrazine-2,3-dicarbonitrile, triazolo[1,2-a]indazole-trione, and spiro triazolo[1,2-a]indazole-tetraone derivatives in an aqueous medium. The catalytic system, reported here, possesses the advantages of both homogeneous and heterogeneous catalysts and can be repetitively used in water. Graphical Abstract& Ahmad Shaabani a-

NaBrO3/guanidinium-based sulfonic acid: as a transition metal- and strong inorganic acid-free oxidation system for alcohols and alkyl arenes

“…In our previous report, a simple procedure for the synthesis of TMG-SO 3 H as an acidic organocatalyst was disclosed for the first time. 36 The catalyst is simply prepared by dropwise addition of chlorosulfonic acid to a n-hexane mixture of tetramethyl guanidine (TMG) at 0 1C (Scheme 2).…”

“…[29][30][31][32][33][34][35] Despite this wealth of functionality present in guanidine, the synthesis of a guanidinium-based Brønsted acid was only reported very recently. 36 In continuation of our efforts to introduce a new and efficient strategy for various organic transformations, [37][38][39][40][41] herein, we report the oxidation of a wide range of alcohols and alkyl arenes to the corresponding aldehydes and ketones using sodium bromate in the presence of guanidinium-based sulfonic acid (1,1,3,3-tetramethylguanidine sulfonic acid: TMG-SO 3 H) as…”

Recent advances in catalytic silylation of hydroxyl‐bearing compounds: A green technique for protection of alcohols using Si–O bond formations

“…Brønsted acid catalysis is a rapidly growing area of organocatalysis. [131][132][133][134][135][136][137][138] Brønsted acids have long been used as catalysts in organic chemistry. [117,[139][140][141][142][143] However, early application of Brønsted acids was rather limited to certain types of reactions, such as hydrolysis and formation of esters, and acetals.…”

Organic Synthesis Using Environmentally Benign Acid Catalysis

“…The functionalization of organocatalysts with Brønsted acid groups creates acidic organocatalysts suitable to perform con-ventional Brønsted acid-catalyzed reactions. A guanidinium-based sulfonic acid functionalized organocatalyst was developed and proved its effectiveness to replace the traditional liquid mineral acids for the multi-component synthesis of a variety of quinoxaline-, pyrazine- and urazole-derivatives in aqueous media (Scheme 60 ) [ 151 ]. The reactions proceeded smoothly in less than two hours at room temperature or reflux depending on the substrate type.…”