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

Polyethylenimine-based non-viral gene delivery systems.

Benjamin H. Rotstein,†,‡ Serge Zaretsky,† Vishal Rai,†,§ and Andrei K. Yudin*,† †Davenport Research Laboratories, Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario Canada, M5S 3H6 ‡Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, and Department of Radiology, Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States Department of Chemistry, Indian Institute of Science Education and Research (IISER) Bhopal, Indore By-pass Road, Bhauri, Bhopal 462 066, MP India

Small Heterocycles in Multicomponent Reactions

Living polymerization techniques can be used to achieve a high degree of control over polymer chain architecture. Examples of the type of polymers that can be synthesized include block copolymers, comb-shaped polymers, multiarmed polymers, ladder polymers, and cyclic polymers. This control of structure, in turn, results in polymers with widely diverse physical properties, even though they are made from readily available low-cost monomers.

https://science.sciencemag.org/content/sci/251/4996/887.full.pdf

Living Polymerization Methods

Thermosensitive water-soluble copolymers with doubly responsive reversibly interacting entities

Isomerization Polymerization of 2-Oxazoline. IV. Kinetic Study of 2-Methyl-2-oxazoline Polymerization

Pure unsubstituted 2-oxazoline (OXZ) was first prepared in good yields by modifying Wenker’s method.1 OXZ was found to polymerize by cationic catalyst in an aprotic polar solvent to give a solid polymer. The polymerization of OXZ in less-polar solvents gave polymer in much decreased yields. Lewis acids such as BF3OEt2 and SbF5, sulfonates, sulfate esters, mineral acids, and alkyl iodide were effective as the polymerization catalyst. But metal chlorides such as SnCl4 and SbCl5 were ineffective. The polymer was a white powder, which was soluble in water and insoluble in most organic solvents. The polymer was shown to be crystalline by X-ray diffraction diagram (mp ca. 210°C). The molecular structure of the polymer proved to be poly(N-formylethyleneimine) by NMR and IR spectra. Alkaline hydrolysis of poly-OXZ gave crystalline polyethyleneimine (mp 58.5°C).

/pdf/isomerization-polymerization-of-2-oxazoline-i-preparation-of-1tf1cnewdw.pdf

Hiroyasu Fujii

Papers

Isomerization Polymerization of 2-Oxazoline. IV. Kinetic Study of 2-Methyl-2-oxazoline Polymerization

Isomerization Polymerization of 2-Oxazoline. I. Preparation of Unsubstituted 2-Oxazoline Polymer

Isomerization Polymerization of 2-Oxazoline. V. Kinetic Studies on the Polymerization of 2-Oxazoline

Alternating Copolymerization of 2-Oxazoline with β-Propiolactone

Reaction of carbonyl compound with isocyanide