Abstract
The Suzuki–Miyaura cross-coupling reaction plays a fundamental role in modern synthetic organic chemistry, both in academia and industry. For this reason, scientists continue to search for new, more effective, cheaper and environmentally friendly procedures. Recently, micellar synthetic chemistry has been demonstrated to be an excellent strategy for achieving chemical transformations in a more efficient way, thanks to the creation of nanoreactors in aqueous environments using selected surfactants. In particular, the cheap and commercially available surfactant Kolliphor EL (a polyethoxylated castor oil derivative) has been used with success to achieve metal-catalyzed transformations in water with high yields and short reaction times, with the advantage of using air-sensitive catalysts without the need for inert atmosphere. In this work, the Kolliphor EL methodology was applied to the Suzuki cross-coupling reaction between thiophene and aniline, using the highly effective catalyst Pd(dtbpf)Cl2. The cross-coupling products were achieved at up to 98% yield, with reaction times of up to only 15 min, working at room temperature and without the need for inert atmosphere.
Highlights
Since its discovery in 1979 [1], the Suzuki–Miyaura cross-coupling reaction has been used as an election tool for organic synthesis, both in discovery chemistry and manufacturing processes, due to its broad functional-group tolerance; its reproducibility; and its use of stable, environmentally benign, inexpensive and readily prepared boron reagents [2,3,4,5,6]
Surfactant-mediated micellar catalysis has emerged in the field of organic chemistry, allowing synthetic transformation in water with excellent results in term of reaction kinetics, yields and ecocompatibility [7,8,9,10]
Mono-thienylanilines were efficiently prepared using a 2 w% Kolliphor EL water solution at rt under air for 15 min starting from bromoanilines, while cosolvent addition, at a slightly higher temperature for 1 h of reaction time, was needed when starting from aniline boronic acid or esters
Summary
Since its discovery in 1979 [1], the Suzuki–Miyaura cross-coupling reaction has been used as an election tool for organic synthesis, both in discovery chemistry and manufacturing processes, due to its broad functional-group tolerance; its reproducibility; and its use of stable, environmentally benign, inexpensive and readily prepared boron reagents [2,3,4,5,6]. Despite the huge advances attained after its introduction, there is still room for improvement, in particular regarding the use of ecocompatible reaction media and shorter reaction times to minimize energy consumption in scaling processes. Surfactant-mediated micellar catalysis has emerged in the field of organic chemistry, allowing synthetic transformation in water with excellent results in term of reaction kinetics, yields and ecocompatibility [7,8,9,10]. The commercially available surfactant Kolliphor EL (a polyethoxylated castor oil, shown in Figure 1) has been proven to form oxygen free micelles, enabling cross-coupling reactions without the need for deoxygenation of the reaction environment [17,18]
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