Combined heterogeneous metal/organic catalysts for eco-friendly synthesis

Abstract

The interplay and synergistic cooperation between homogeneous and heterogeneous catalyst systems is of utmost importance in nature. It is also applied in chemical synthesis. Here, it can allow for new reactivity, which is not possible by the employment of a single catalyst, and promote the catalysis of multiple transformations in a one-pot sequence. This could overall lead to novel reactions and the development of sustainable chemistry. In this context, a versatile and broad synergistic strategy for the selective synthesis of valuable molecules with variable complexity and under eco-friendly conditions is disclosed. It is based on integrated heterogeneous metal/organo multiple relay catalysis, which is performed in a single reaction vessel, and allows for the assembly of complex molecules (e.g., heterocycles and carbocycles) with up to three quaternary stereocenters in a highly enantioselective fashion from simple alcohols and air/O 2 .

Integrated Heterogeneous Metal/Enzymatic Multiple Relay Catalysis for Eco-Friendly and Asymmetric Synthesis

“…This could also lead to efficient recycling with consequent economic and environmental advantages. Heterogeneous palladium catalysts can also be efficiently combined with simple chiral amine cocatalysts without loss of their reactivity . Hence, there might be a chance of discovering a highly chemoselective reductive amination using ammonium formate and a heterogeneous palladium catalyst.…”

Recent Developments in Palladium-Catalyzed Oxidative Cascade Carbocyclization

“…In addition, the combination of heterogeneous Pd(0) species (Pd(0)-aminopropyl-mesocellular foam (Pd 0 -Amp-MCF)) or Pd(0)-aminopropyl-controlled pore glass (Pd 0 -Amp-CPG))/chiral aminocatalysis also exhibited a wide substrate scope under the same conditions in comparison to the case when Pd­(PPh 3 ) 4 is used as a homogeneous cocatalyst …”

Asymmetric one-pot reactions using heterogeneous chemical catalysis: recent steps towards sustainable processes

“…The scope of the heterogeneous relay catalytic process was investigated using 7 or the oxindole derivative 94, 162 the latter resulting in spirolactams 95 with various unsaturated aldehydes 6. [108][109][110] However, recycling of the catalyst was not successful, due to deactivation of the surface bonded chiral amine as a consequence of the inhibition by the aldehyde or by the product. Recently, multi-hollow organic microspheres containing anchored CA6* organocatalyst were prepared by solvent etching the poly(styrene/acrylic acid) core of microparticles having a chiral copolymer shell.…”

“…106 Later, the cascade reaction was complemented by the in situ preparation of the α,β-unsaturated aldehyde in a one-pot manner by oxidation of the corresponding allylic alcohols (13) with O 2 . [107][108][109] Although the supported Pd catalysed both the oxidation and the final carbocyclization steps, the reaction temperature was modified and 7 and CA6* was introduced following the oxidation of the allylic alcohol, leading to sequential one-pot reactions coupled with the above cascade process, as illustrated in Scheme 4. Heterogeneous catalysts prepared by immobilization of PdIJII) species over polyimine or azolinked porous polymer supports were also successfully used.…”