Zur Synthese sulfonierter Derivate von 4‐Amino‐1,3‐dimethylbenzol und 2‐Amino‐1,3‐dimethylbenzol

Abstract

Syntheses of Sulfonated Derivatives of 4‐Amino‐1, 3‐dimethylbenzene and 2‐Amino‐1, 3‐dimethylbenzene Direct sulfonation of 4‐amino‐1, 3‐dimethylbenzene (1) and sulfonation of 4‐nitro‐1,3‐dimethylbenzene (4) to 4‐nitro‐1,3‐dimethylbenzene‐6‐sulfonic acid (3) followed by reduction yield 4‐amino‐1,3‐dimethylbenzene‐6‐sulfonic acid (2). The isomeric 5‐sulfonic acid (5) however is prepared solely by baking the acid sulfate salt of 1. Reaction of sulfur dioxide with the diazonium chloride derived from 2‐amino‐4‐nitro‐1,3‐dimethylbenzene (7) leads to 4‐nitro‐1,3‐dimethylbenzene‐2‐sulfonyl chloride (8), which is successively hydrolyzed to 4‐nitro‐1,3‐dimethylbenzene‐2‐sulfonic acid (9) and reduced to 4‐amino‐1, 3‐dimethylbenzene‐2‐sulfonic acid (6). Treatment of 4‐amino‐6‐bromo‐1,3‐dimethylbenzene (12) and 4‐amino‐6‐chloro‐1, 3‐dimethylbenzene (13), the former obtained by reduction of 4‐chloro‐6‐nitro‐1,3‐dimethyl‐benzene (10) and the latter from 4‐chloro‐6‐nitro‐1, 3‐dimethylbenzene (11), with oleum yield 4‐amino‐6‐bromo‐1,3‐dimethylbenzene‐2‐sulfonic acid (14) and 4‐amino‐6‐chloro‐1,3‐dimethylbenzene‐2‐sulfonic acid (15) respectively; subsequent carbon‐halogen hydrogenolyses of 14 and 15 lead also to 6 (Scheme 1). Baking the acid sulfate salt of 2‐amino‐1, 3‐dimethylbenzene (17) gives 2‐amino‐1, 3‐dimethylbenzene‐5‐sulfonic acid (16), whereas the isomeric 4‐sulfonic acid (18) can be prepared by either of the following three possible pathways: Sulfonation of 2‐nitro‐1,3‐dimethylbenzene (20) to 2‐nitro‐1,3‐dimethylbenzene‐4‐sulfonic acid (21) followed by reduction or sulfonation of 2‐acetylamino‐1,3‐dimethylbenzene (19) to 2‐acetylamino‐1,3‐dimethylbenzene‐4‐sulfonic acid (22) with subsequent hydrolysis or direct sulfonation of 17. Further sulfonation of 18 yields 2‐amino 1,3‐dimethylbenzene‐4,6‐disulfonic acid (23), the structure of which is independently confirmed by reduction of unequivocally prepared 2‐nitro‐ 1,:3‐dimethylbenzene‐4,6‐disulfonic acid (24)(Scheme 2).

Aqueous Suzuki coupling reaction catalyzed by water-soluble diimine/Pd(II) systems

“…Alkyl substituted sulfonated aniline sodium salts [35,36], Disulfonated diimine ligands [37,38] and [Bmim]Cl [39] were pre- pared according to literature methods. All solvents were purchased and purified according to standard methods.…”

Synthesis and catalytic applications of sulfonate β-ketoimine and β-diimine in the Suzuki reaction in aqueous phase

“…Synthesis of sulfonated b-ketoimines and b-diimines 2,6-Dialkyl anilines were sulfonated at 180-190°C with concentrated sulfuric acid in yields of 65-75% (Scheme 1) [25,26].…”

An efficient and recyclable water-soluble cyclopalladated complex for aqueous Suzuki reactions under aerial conditions

“…The sodium salts of 3,5-dialkyl sulfanilic acid [38,39] and the benzaldehyde imine ligands [30] were prepared by modifications of literature procedures. All other reagents were used as received from commercial sources.…”