A review: Non-cross-linked polystyrene bound reagents, catalysts and syntheses

Polyaniline coated on celite, a heterogeneous support for palladium: applications in catalytic Suzuki and one-pot Suzuki–aldol reactions

Polyaniline was heterogenized on celite particles and used as a support for palladium metal ions. The catalyst was found to be effective in Suzuki–Miyaura and its one-pot aldol reactions.

Multivalent polyglycerol supported imidazolidin-4-one organocatalysts for enantioselective Friedel-Crafts alkylations

The first immobilization of a MacMillan’s first generation organocatalyst onto dendritic support is described. A modified tyrosine-based imidazolidin-4-one was grafted to a soluble high-loading hyperbranched polyglycerol via a copper-catalyzed alkyne–azide cycloaddition (CuAAC) reaction and readily purified by dialysis. The efficiency of differently functionalized multivalent organocatalysts 4a–c was tested in the asymmetric Friedel–Crafts alkylation of N-methylpyrrole with α,β-unsaturated aldehydes. A variety of substituted enals was investigated to explore the activity of the catalytic system which was also compared with monovalent analogues. The catalyst 4b showed excellent turnover rates and no loss of activity due to immobilization, albeit moderate enantioselectivities were observed. Moreover, easy recovery by selective precipitation allowed the reuse of the catalyst for three cycles.

Non-cross-linked polystyrene-supported 2-imidazolidinone chiral auxiliary: synthesis and application in asymmetric alkylation reactions

Asymmetric alkylation reactions using non-cross-linked polystyrene (NCPS)-supported 2-imidazolidinone chiral auxiliaries were successfully investigated with excellent diastereocontrol (>99% de). The recovery and the recycling of this soluble polymer-supported chiral auxiliary were achieved in order to produce highly optical pure carboxylic acids.

Removal, Recovery, and Recycling of Triarylphosphonium-Supported Tin Reagents for Various Organic Transformations

Phosphonium-supported tin reagents and catalysts were prepared and were shown to be effective in Stille couplings, radical dehalogenations, radical cyclizations, and carbonyl allylations. Not only could the tin residues be removed from the crude reaction mixture through a phase separation process but also they could be recovered and recycled.