Borax as an Efficient Metal‐Free Catalyst for Hetero‐Michael Reactions in an Aqueous Medium

Abstract

Borax, a naturally occurring material, very efficiently catalyzed the conjugate addition of thiols, dithiols and amines to α,β‐unsaturated ketones, nitriles, amides, aldehydes and esters in an aqueous medium to afford the corresponding Michael adducts in good yields at room temperature. Recycling of the catalyst and scaling up of the reactions are important attributes of this catalysis. The reactions of thiols and dithiols were relatively more facile than those of the corresponding amines. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Development of a microfluidic “click chip” incorporating an immobilized Cu(i) catalyst

“…The silanized chip was annealed at 70 °C under vacuum for 2 h to cure the surface. Ligand 2 (19.5 mg, 29.8 µmol) was dissolved in a 10 mmol% borax solution (1.5 mL), 24 and the solution was sonicated for 20 min. The solution was pumped into the chip at the rate of 10 µL min −1 at 47 °C for 150 min.…”

A simple, economical, and environmentally benign protocol for the synthesis of 2-amino-3,5-dicarbonitrile-6-sulfanylpyridines at ambient temperature

“…and a few model reactions were performed employing potassium phosphate, borax, polyvinyl pyridine (PVP) as well as Amberlite IRA-400 (OH − form) as catalysts. The choice of potassium phosphate as well as borax was based on the mechanism of the reaction as well as on the early reports in using these catalysts in Knoevenagel as well as in thiaMichael addition reactions (38,39,45). On the other hand, the choice of PVP as well as Amberlite IRA-400 (OH − form) was concerned with the possibility of their reuse.…”

Conjugated Addition of Amines to Electron Deficient Alkenes: A Green Approach

“…But usually both these additions are carried out in presence of a strong base or acid [8,9]. Several methods are available in the literature by using different catalysts such as Yb(OTf) 3 [10], CeCl 3 ·7H 2 O-NaI [11], InCl 3 [12], Cu(OTf) 2 [13,14], CAN [15], KF/alumina [16,17], LiClO 4 [18], Bi(OTf) 3 [19], Bi(NO) 3 [20], SmI 2 [21], Cu(acac) 2 /ionic liquid [22], ionic liquid/ quaternary ammonium salt [23,24], boric acid [25], borax [26] [30], MnCl 2 [31]etc. Although these methods have their own advantages and quite useful, but some of these methods used a large excess of reagents, hazardous solvents such as acetonitrile or 1,2-dichloroethane, require long time and harsh reaction.…”