Polytopic Bis(oxazoline)‐Based Ligands for the Development of Recoverable Catalytic Systems Applied to the Cyclopropanation Reaction

Abstract

New ditopic and tetratopic chiral ligands, based on the bis(oxazoline) moiety, have been synthesized and their copper complexes tested as catalysts in the benchmark asymmetric cyclopropanation reaction of styrene with ethyl diazoacetate. The polytopic nature of these ligands enables a release–capture strategy to efficiently recycle the enantioselective catalyst by precipitation of a coordination polymer at the end of the reaction. This strategy enables the self‐supported catalyst to be reused up to 20 times leading to good yields and enantioselectivities.

Chiral catalysts immobilized on achiral polymers: effect of the polymer support on the performance of the catalyst

“…The preparation of polytopic bis(oxazoline)-based ligands allowed obtaining selfsupported catalytic systems in the presence of copper. 304 These coordination polymers re-dissolved in the reaction medium when applied to the enantioselective cyclopropanation of styrene with diazoacetate and then precipitated spontaneously at the end of the reaction. They were reused for up to 20 cycles but a decrease in the activity was observed along with smaller changes in selectivity and enantioselectivity.…”

A High Loading and Recyclable Pentaerythritol Supported Imidazolidin-4-one Catalyst for Enantioselective Diels–Alder Reactions

“…Pentaerythritol is a well known, cheap, atoxic, widely used chemical raw materials, and it is considered to be ideal building blocks in many areas of materials chemistry [32][33][34] and in the synthesis of dendrimers [35][36][37]. Because of its low molecular weight and its special molecular structure, the loading capacity of pentaerythritol is higher than many other kind of supports such as traditional polymer support [10-12, 14, 16, 22], ionic liquid [17][18][19][20] and tetraarylphosphonium salt [28,29].…”

Microwave-promoted solventless Mizoroki–Heck reactions catalysed by Pd nanoparticles supported on laponite clay

“…The yield increase observed in some cycles may be due to incomplete product extraction in the precedent cycles, a situation that is common with a low polar solvent is used to extract products from a heterogeneous catalyst. 44 The particle size of the clay support largely decreases upon catalyst reuse. This seems to be due to extensive delamination of the clay structure in reaction conditions, as shown by the SEM micrographs of the exhaust catalyst (Fig.…”