In this review, we describe the recent advances in supramolecular helical assemblies formed from chiral and achiral small molecules, oligomers (foldamers), and helical and nonhelical polymers from the viewpoints of their formations with unique chiral phenomena, such as amplification of chirality during the dynamic helically assembled processes, properties, and specific functionalities, some of which have not been observed in or achieved by biological systems. In addition, a brief historical overview of the helical assemblies of small molecules and remarkable progress in the synthesis of single-stranded and multistranded helical foldamers and polymers, their properties, structures, and functions, mainly since 2009, will also be described.

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

2. Essential Components: Earlier Developments 5449 2.1. Activated alkenes/alkynes 5450 2.1.1. Acyclic activated alkenes/ alkynes 5450 2.1.2. Cyclic activated alkenes 5451 2.2. Electrophiles 5451 2.3. Catalysts 5452 3. Essential Components: Recent Developments 5452 3.1. Activated Alkenes/Alkynes 5452 3.2. Electrophiles 5460 3.3. Catalysts 5477 4. Asymmetric Baylis-Hillman Reaction: Earlier Developments 5495

Recent contributions from the Baylis-Hillman reaction to organic chemistry.

Using soluble polymer supports to facilitate homogeneous catalysis.

A magnetic nanoparticle-supported quinuclidine was prepared and evaluated as a recoverable Morita-Baylis-Hillman catalyst. The supported catalyst 2 demonstrated comparable activity with that of DABCO and could be simply recycled with the assistance of an external magnet. The thus recycled catalyst could be reused for 7 times without significant loss of activity.

Magnetic Nanoparticle‐Supported Morita–Baylis–Hillman Catalysts

Dendrimers provide new and practical solutions to the complex problem of catalyst separation from the product stream. Dendrimers functionalized with active metal complexes are themselves soluble, nanosized catalysts that are capable of combining the high activity and selectivity of classical homogeneous catalysts with the enhanced separation capabilities added by the macromolecule. This report reviews the recovery and recycling of metallodendrimer catalysts by different separation techniques, such as nanofiltration, precipitation, or catalyst immobilization on solid supports, or by the use of appropriate solvent media, as illustrated by representative examples.

Dendrimers: Solutions For Catalyst Separation and Recycling–A Review† † Dedicated to the memory of Dr. José Antonio Delgado Oyagüe.

The Baylis–Hillman reaction of various aryl aldehydes with methyl vinyl ketone and acrylonitrile in the thermomorphic binary system (DMF/cyclohexane, 1/1, v/v) has been investigated. The phase selectively soluble alkyl-modified dendritic DMAP catalyst could be easily recycled via phase separation which was induced by cooling the temperature from 60 °C to room temperature. The corresponding Baylis–Hillman adducts were obtained in good yields and the recycled and reactivated dendritic catalyst almost gave the same results.

Phase selectively soluble dendritic derivative of 4-(n,n-dimethylamino)pyridine : an easily recyclable catalyst for Baylis-Hillman reactions

The application of non-imidazolium-based ionic liquid [EtPy][BF4] (N-1-ethylpyridinium tetrafluoraborate) as recyclable solvent for the Baylis–Hillman reactions was presented. Compared with the commonly used imidazolium-based ionic liquid [bmim][PF6] (1-n-butyl-3-methylimidazolium hexafluorophosphate) and [bdmim][PF6] (1-n-butyl-2,3-dimethylimidazolium hexafluorophosphate) that evidently reacts with aldehydes under basic conditions, ionic liquid [EtPy][BF4] is inert and the Baylis–Hillman reactions in [EtPy][BF4] proceed quickly with good yields.

Application of non-imidazolium-based ionic liquid in the Baylis-Hillman reactions : Rate and yield promoted

Optically active helical vinyl polymers via helix-sense-selective anionic polymerization of (S)-3-vinyl-2,2′-bis(methoxymethoxy)-1,1′-binaphthyl

Several novel epoxy monomers, (S,S)- or (S,R)-3-(glycidyloxy)methyl-2,2′-bis(methoxymethyloxy)-1,1′-binaphthalene and (S,S)- or (S,R)-6-(glycidyloxy)methyl-2,2′-bis(methoxymethyloxy)-1,1′-binaphthalene, which were derived from chiral BINOL and epichlorohydrin, were synthesized and underwent anionic polymerization and deprotection of the MOM groups to obtain soluble polyethers. These polyethers were used to induce the enantioselective borane reduction of prochiral ketones. The substrates gave up to 98% yield with over 99% ee values. The recovered polyethers could be reused many times to induce the enantioselective reduction of prochiral ketones without losing their enantioselective induction ability.

Synthesis of several polyethers derived from BINOL and their application in the asymmetric borane reduction of prochiral ketones

Two novel polyethers derived from BINOL were synthesized and used to induce the enantioselective borane reduction of prochiral ketones. The polyethers gave the expected secondary alcohols with up to 98% yields and over 99% ee values. The recovered polyethers could be reused for many times to induce the enantioselective reduction of prochiral ketones without losing their enantioselective induction ability.

Li-Wen Yang

Papers

Phase selectively soluble dendritic derivative of 4-(n,n-dimethylamino)pyridine : an easily recyclable catalyst for Baylis-Hillman reactions

Application of non-imidazolium-based ionic liquid in the Baylis-Hillman reactions : Rate and yield promoted

Optically active helical vinyl polymers via helix-sense-selective anionic polymerization of (S)-3-vinyl-2,2′-bis(methoxymethoxy)-1,1′-binaphthyl

Synthesis of several polyethers derived from BINOL and their application in the asymmetric borane reduction of prochiral ketones

Chiral polyethers derived from BINOL and ECH as highly enantioselective and efficient catalysts for the borane reduction of prochiral ketones