The legacy of Gilbert Newton Lewis (1875-1946) pervades the lexicon of chemical bonding and reactivity. The power of his concept of donor-acceptor bonding is evident in the eponymous foundations of electron-pair acceptors (Lewis acids) and donors (Lewis bases). Lewis recognized that acids are not restricted to those substances that contain hydrogen (Bronsted acids), and helped overthrow the "modern cult of the proton". His discovery ushered in the use of Lewis acids as reagents and catalysts for organic reactions. However, in recent years, the recognition that Lewis bases can also serve in this capacity has grown enormously. Most importantly, it has become increasingly apparent that the behavior of Lewis bases as agents for promoting chemical reactions is not merely as an electronic complement of the cognate Lewis acids: in fact Lewis bases are capable of enhancing both the electrophilic and nucleophilic character of molecules to which they are bound. This diversity of behavior leads to a remarkable versatility for the catalysis of reactions by Lewis bases.

Lewis Base Catalysis in Organic Synthesis

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.

Nucleophilic phosphine catalysis has proven to be a powerful tool in organic synthesis, which can provide easy access to cyclic, bicyclic or polycyclic carbocycles and heterocycles. Owing to their comparatively strong and readily tunable nucleophilicity, phosphines can be easily tailored to efficient annulation reactions with good control over reaction selectivity. This has resulted in a tremendous increase in their scope and in a concomitant number of reports where phosphine-triggered annulation reactions occur. This tutorial review summarizes the recent achievements in this area.

Phosphine-triggered synthesis of functionalized cyclic compounds

Organic Polymer Supports for Synthesis and for Reagent and Catalyst Immobilization

Using soluble polymer supports to facilitate homogeneous catalysis.

A series of soluble, non-cross-linked polystyrene-supported triphenylphosphane and 4-dimethylaminopyridine reagents were prepared. Some of these polymeric reagents contained either alkyl alcohol or phenol groups on the polymer backbone. The use of these materials as organocatalysts in a range of Morita-Baylis-Hillman reactions indicated that hydroxyl groups could participate in the reactions and accelerate product formation. In the cases examined, phenol groups were more effective than alkyl alcohol groups for catalyzing the reactions. This article is one of the first reports of the synthesis and use of non-natural, bifunctional polymeric reagents for use in organic synthesis in which both functional groups can cooperatively participate in the catalysis of reactions.

Bifunctional polymeric organocatalysts and their application in the cooperative catalysis of Morita-Baylis-Hillman reactions.

A study of the effect of Michael acceptor stereochemistry on the efficiency of intramolecular Morita−Baylis−Hillman (MBH) reactions has been performed. The reactions were catalyzed by a phosphine, and the reaction substrates studied were enones containing a pendant aldehyde moiety attached at the β-position of the alkene group. In all cases examined with PPh3 as the catalyst, cyclization substrates possessing (Z)-alkene stereochemistry afforded a much higher yield of the desired product than did the E isomeric substrates under identical reaction conditions. This was also true when a polymer-supported phosphine catalyst was used. While both alkene isomers afforded the same product, in parallel reactions, the Z isomer afforded 2.5−8.5 times higher yield than did the corresponding E isomer. It is proposed that steric effects are a possible source of this dramatic difference in reactivity. Substrates where the β-substituent is cis to the electron-withdrawing substituent are relatively more accessible to react...

Rui Huang

Papers

Bifunctional polymeric organocatalysts and their application in the cooperative catalysis of Morita-Baylis-Hillman reactions.

Influence of Michael acceptor stereochemistry on intramolecular Morita-Baylis-Hillman reactions.

Influence of Michael Acceptor Stereochemistry on Intramolecular Morita—Baylis—Hillman Reactions.

Bifunctional Polymeric Organocatalysts and Their Application in the Cooperative Catalysis of Morita—Baylis—Hillman Reactions.