Third-Liquid Phase Transfer Catalysis for Horner–Wadsworth–Emmons Reactions of “Moderately Acidic” and “Weakly Acidic” Phosphonates

Abstract

Horner-Wadsworth-Emmons (HWE) reaction was investigated in green thirdliquid phase-transfer catalysis (TLPTC) system. With 6% equiv of the catalyst and 50% NaOH aqueous solution, the third phase was generated. In this TLPTC system, HWE reactions of benzaldehydes bearing electron-donating group with "weakly" or "moderately" acidic phosphonates proceeded in high yield (>90%) with all E-isomer product (stilbene). Teraoctyl ammonium bromide (TOAB) afforded a high yield of 93% for HWE reaction of benzaldehydes with electron-withdrawing groups. It was found that the ratio of E-stilbene to Z-stilbene was also influenced by the steric hindrance of the achiral quaternary ammonium salt catalyst. The isolated yield and geometric selectivity for HWE reaction kept unchanged in four consecutive runs of both the third and the aqueous phase. Highly efficient and practical hydroxide-initiated TLPTC system was developed for HWE reaction.

Design and Development of Novel Continuous Flow Stirred Multiphase Reactor: Liquid–Liquid–Liquid Phase Transfer Catalysed Synthesis of Guaiacol Glycidyl Ether

“…At the lower end of the reactor, a drain valve (19) was installed. Three feed vessels (24,25,26) were used to store each phase feed. Three single piston pumps (21,22,23) with pulse dampeners were used to pump each phase at the respective inlets.…”

“…Additionally, there are reactions like esterification of potassium 4-methoxyphenylacetate [16], sodium benzoate [17], synthesis of n-butyl salicylate by esterification of sodium salicylate [18], benzoylation of sodium 4-acetylphenoxide [19], 4-chloro-3-methylphenol sodium salt [20], synthesis of butyl salicylate [21], benzyl salicylate [22], and ultrasound-assisted synthesis of dialkyl peroxides [23]. Recently, the Horner−Wadsworth−Emmons (HWE) reaction was studied using an L-L-L PTC system [24][25][26].…”

Catalytic Process for the Hydroxide-Initiated Reaction of the “Weakly Acidic” Substrate in the Third-Liquid Phase-Transfer Catalytic System

“…24,25 To explore more green and practical reaction systems, Horner−Wadsworth−Emmons (HWE) reaction of various phosphonates proceeded in the TLPTC system in our previous research. 26,27 For HWE reaction of "weakly acidic" substrates in the TLPTC system, it was found that the bond-forming reaction occurred both in the third phase and the organic phase. Accordingly, the kinetics model containing the organic phase cycle and the third-phase cycle was proposed.…”