An E-Factor Minimized Protocol for a Sustainable and Efficient Heck Reaction in Flow

Abstract

A highly sustainable and waste-minimized protocol for Heck coupling has been defined. Optimal conditions have been defined by exploiting a heterogeneous catalyst based on supported ionic liquid-like phases featuring high Pd loading (10 wt %) and by optimizing its efficiency in a recoverable green reaction medium (acetonitrile/water azeotrope). Pure products 4a–l and 6a–h have been isolated chromatography-free in high yields (74–99%) and with extremely low environmental factor (E-factor) values (2.3–5.0). With the application of flow technology, the selected heterogeneous base and Pd catalyst have been fully recovered and reused, and minimum palladium leaching allowed for isolation of the final products with low residual palladium content (<5 ppm) without any purification step

Halloysite nanotubes as support for metal-based catalysts

“…kaolinite sheets of octahedral gibbsite Al(OH) 3 and tetrahedral SiO 4 . 33 The different layers are linked to each other by hydrogen bonds formed between oxygen atoms of the tetrahedral sheet and inner-surface OH groups of the octahedral sheets (Fig.…”

Definition of green synthetic tools based on safer reaction media, heterogeneous catalysis, and flow technology

“…Consequently, in most of the cases these aqueous mixtures cannot be easily recovered resulting in the significant production of a costly waste. We have recently reported the use of acetonitrile azeotrope in several cross-coupling reactions [39][40][41] but most recently we have focused our attention on waste minimized protocols for copper-catalyzed azide alkyne cycloaddition (CuAAC) a typical click reaction [42,43], widely applied in countless areas for the preparation of target materials. For recent representative examples see [44][45][46] and literature cited herein.…”

“…We are directing our efforts in the use of different supports such as silica [39,40,57,58], zirconium phosphate or phosphonates [41,[59][60][61], and cross-linked polystyrenes [62,63].…”

“…The flow technology combined with the use of recoverable reaction media has allowed to develop sustainable methods for the heterogeneous palladium-catalyzed Suzuki-Miyaura, and Heck cross-coupling reactions [40,41,57,61].…”

Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications

“…The catalyst was used three times without loss of catalytic activity. A novel and highly sustainable protocol for flow Heck reaction in presence of the catalyst 138, constituted by palladium (10 wt %) supported on cross-linked imidazolium network, was reported (Scheme 51) [83]. Flow reactors and protocols were defined in order to optimize the recovery and reuse of the catalyst, minimize waste and in particular, the amount of organic solvent needed to isolate the final products.…”