Deep Eutectic Solvent: An Efficient Catalyst for C-O Coupling Reactions.

Abstract

An efficient and facile route has been developed by using greener and reusable deep eutectic solvent (DES) for the synthesis of O-arylated ethers. This process involves nucleophilic aromatic substitution (S N Ar) of various strongly electrondeficient aryl/alkyl halides and phenols with different substituents resulting in good to excellent yields of products (80-96 %). A significant enhancement in the yield as well as rate of the reaction is observed with increase in presence of electron-withdrawing functionality attached to aryl halide moiety. Simplicity of this catalytic system, cheap cost and easy product isolation procedure makes this protocol economically viable and comparable to metal/ligand catalysed reactions utilizing aprotic solvents. Moreover, the other significant advantages of this method includes mild reaction conditions, short reaction times, easy work up procedure and recyclability of the catalyst up to four runs without remarkable loss in activity.

Deep Eutectic Solvent: An Efficient and Recyclable Catalyst for Synthesis of Thioethers.

“…The proposed mechanism for C−S bond formation is illustrated in Figure which is in well agreement with experimental observations and literature reports , The enhanced reactivity of aryl halides bearing an electron‐withdrawing group and no reactivity for electron‐donating substrate implies that the reactions proceeds through S N Ar mechanistic pathway.The hydrogen bonding interactions of DES with aryl halide and p‐thiocresol is responsible for increasing electrophilicity of aryl halide and nucleophilicity of the latter, thereby assisting the attack of p‐thiocresol resulting in product formation.…”

“…have recently reported an incredible work on S N Ar reactions using imidazolium‐based ILs, However in contrast to these conventional ILs, DES have remarkable advantages such as being bio‐degradable, non‐toxic, recyclable and insensitive towards moisture. In our earlier work, we have reported C−O and C−N bond formation using DES, this work is continuation of our prior work, involving an effective strategy devoid of metal and aprotic solvents for the formation of C−S bond using DES as catalyst. To our best knowledge, this is an innovative methodology which reports DES catalyzed S N Ar reactions in the synthesis of thioethers.…”

Choline Hydroxide Promoted Synthesis of N‐Aryl Anthraquinone Derivatives: Metal Free Approach to Ullmann Coupling Reactions

“…Based on the experimental observations and literature reports the reaction mechanism for formation of N ‐aryl AQ in the presence of ChOH is depicted in Figure . The enhanced reactivity of 1‐bromo‐AQ towards N ‐arylation reaction is due to electron‐withdrawing carbonyl group suggesting S N Ar mechanistic pathway.…”

“…Choline hydroxide (ChOH) is an environmentally benign, water soluble and biodegradable task‐specific ionic liquid which displays strong basicity . In our prior work we have reported C−N, C−O and C−S coupling reactions catalysed by deep eutectic solvents (DES) . In continuation of our endeavours in developing environmentally benign catalysts and overcoming the afore mentioned limitations, we wish to report choline hydroxide catalysed metal free protocol for synthesis of N ‐aryl anthraquinone derivatives.…”

Application of Deep Eutectic Solvents in Formation of Carbon‐Carbon and Carbon‐Heteroatom Bond by Cross‐Coupling Reactions

“…Despite of the development of coupling reactions for the synthesis of CÀ O bonds is relatively mature, these reactions still suffer from serious troubles, such as elevated reaction temperatures, long reaction times, low yields, formidable purification problems, the usual requirement for stoichiometric quantities of complex catalysts and difficulties in recovery, and the use of strong polar toxic solvents, which limit the implementation of their application in industrial production. [60] Expanding on previous studies, Pant [60] exploited an efficient and facile reaction route for the SNAr of electron-deficient aryl groups, alkyl halides and phenols with different substituents in DESs to give the desired product in good to excellent yields (80-96 %) (Figure 22). It was demonstrated that the rise of the electron-absorbing functional groups attached to the aryl halide led to a significant increase in yield and reaction rate.…”