Palladium Catalyzed Electrophilic C2‐Arylation of Azoles by Aryltriazenes in Ionic Liquid Promoted by Acidic Ionic Liquid

Abstract

A green C−H bond activation of azole based bio‐pertinent substrates such as benzoxazole, benzothiazole, benzimidazole are accomplished using readily prepared 1‐aryltriazenes as arylating agent. Under an optimized condition employing Pd(OAc)2 and CuI in either hydrophilic [Bmim][BF4] or hydrophobic [Bmim][PF6] IL medium with [BMIM(SO3H)][OTf] as a promoter, these arylation reactions proceeded smoothly to afford 2‐aryl substituted azoles in acceptable to better yields besides noticeable functional group tolerance. The prospective for recovery and re‐use of ionic liquid solvent is demonstrated.

Ultrasonic Assisted Facile Synthesis of N‐Arylamides Using Nitriles and 1‐Aryltriazenes Precursors Promoted by Brønsted Acidic Ionic Liquid under Metal‐Free Conditions

“…Different 1‐aryltriazenes were synthesized from the different aromatic amines and diverse secondary amines by known general method and used after recrystallization suitable solvent [8d–f,9, 11,12] . Data in Table 1 reveals the complete overview of the optimizations executed to develop method for N‐arylamides synthesis using conventional heating and under sonication.…”

“…These drawbacks make the available optimized processes less suitable on the grounds of green chemistry aspects. In our long pursuit of developing sustainability and greener strategies, we have recently established green synthetic methodologies employing [BMIM(SO 3 H)][OTf] and guanidine based ionic liquids (IL) as promoter under conventional heating or microwave irradiation: for example, synthesis of N‐arylamides [8a,13h] using 1‐aryltriazenes as a coupling partner [8a,13h] and Ritter type chemistry employing arylnitriles [8b,e] as nitrogen donor including various other kind of green transformations [8]…”

“…Thus, in an endeavor to develop green methodologies, [8] and to understand the possible synergistic effect between US and IL than the conventional approach towards promoting the synthesis of N ‐arylamides, the present piece of work is designed with Brønsted acidic ionic liquid as promoter, 1‐aryltriazenes [8d–f] as aryl electrophile precursor and aliphatic/arylnitriles as amine source.…”

Copper Catalyzed N‐Arylation of Amines in Ionic Liquid Using 1‐Aryltriazenes as Aryl Surrogates

“…Morpholine, piperidine and pyrrolidine based aryltriazenes were synthesized from the different aromatic amines by known general method and used after recrystallization from ethyl alcohol [11,13,16b] . To start with, optimization studies were carried out employing 1 mmol of morpholine based phenyltriazene, 1.1 mmol of aniline, 20 mol % of catalyst, 1 eq of IL promotor and 3–4 mL of IL solvent at 60–65 °C as the standard reaction condition for this C−N cross‐coupling as depicted in Table 1.…”

“…Alternatively, use of 1‐aryltriazene as electrophile is more appealing and promising due to its simple preparation, stability and facile access of diverse derivatives. Employing this as in‐situ generated electrophilic partner, reactions such as Suzuki, [10] Heck, [11] C‐2‐arylation, [12,13] diazenylation [14] and 1,2 diketone synthesis [15] were well explored either in conventional volatile organic solvents (VOCs) or in other green solvents. Recent years have witnessed increased interest of ionic liquids either as solvent, catalyst, additive or all together for many chemical transformations.…”