Palladium-catalyzed coupling of azoles with 1-aryltriazenes via C–H/C–N cleavage

Abstract

Arylation of azoles was performed via C–H functionalization with 1-aryltriazenes in the presence of PdCl2, dppe, CuCl and ButOLi.

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

“…Furthermore, use of MsOH in place of Bronsted acidic IL did not give fruitful result. This optimization process revealed that use of 1.5 mmol of Ar‐triazene, 10 mol% of Pd(OAc) 2 and 1.5eq of CuI, 1eq of [BMIM(SO 3 H)][OTf] in 6–8 mL of [Bmim][X] at 80–90 °C(Tj) is optimal to proceed the desired cross coupling reaction in better yield even without the necessity for a base or ligand . A gram scale reaction imitating our optimized condition furnished reproducible yield as shown in SI file (Table ).…”

“…A very recent report claims C‐2 arylation of azoles employing DMF, a class 2 carcinogenic solvent that is not appropriate in API process industry, at 130 °C in an airtight atmosphere (sealed reactor). Dai and Wang described similar kind of transformation yet again in DMF in the presence of additives such as ligand (dppe) and strong base (Bu t OLi) at 120 °C over a period of 24 h. Driven by these impediments, development of biocompatible, recyclable, and green chemistry methodologies using eco‐friendly and sustainable conditions with an objective of better yields and selectivity are highly desirable. Thus, in an endeavor to overcome these limitations, a greener synthetic protocol towards the access of the target molecule is conceived by the use of ionic liquids as a reaction medium/promoter mainly due to its environmental acceptability.…”

“…Based on our screening studies and available literature, a possible mechanistic pathway is proposed as shown in Scheme . The Bronsted acidic IL facilitates the formation of internal salt with triazene, which intern oxidatively added to in‐situ formed Pd(0) to form an aryl palladium cation with the expulsion of amine and nitrogen.…”

Copper in Efficient Synthesis of Aromatic Heterocycles with Single Heteroatom

“…Primary arylamines and electron-deficient terminal alkynes took part in Cu(II) catalyzed domino reaction gave access for a variety of 2,4-disubstituted quinolines (Scheme 27). [40] The mechanism is believed to involve alkyne homocoupling, followed by hydroamination step and cyclization. Kaeobamrung and co-workers developed a domino reaction of enaminones for synthesis of two different types of quinoline derivatives (Scheme 28).…”

Synthesis of multi‐functionalized quinolines and 1,2‐dihydroquinolines through FeCl3‐mediated reactions of carbonyl compounds with 2‐vinylanilines

“…Nevertheless, the majority of these methods suffer from drawbacks such as strong acidic or basic conditions, high reaction temperatures, long reaction times, excessive oxidants, low regioselectivities, and so on. In recent decades, significant progress has been made in the development of transition‐metal‐catalyzed methods such those using iridium, rhodium, ruthenium, palladium, nickel, gold, silver, copper, and iron because of their functional group tolerance, stero‐ and regioselectivity, and excellent yields under mild reaction conditions. Although these procedures provide efficient routes for assembling the quinoline skeleton, most of them use expensive and often toxic metal catalysts, which often generate heavy metal impurities in the product and limit their large‐scale applications.…”