1 Introduction By JOHN A. JOULEa AND JOHN P. RICHARDb aDepartment of Chemistry The University of Manchester Manchester M13 9PL UK bDepartment of Chemistry University at Buffalo SUNY Buffalo NY 14260–3000 USA In Volume 93 of Annual Reports Section B the Reader will find discussions of work published in 1996 concerning Theoretical Organic Chemistry Polar and Free Radical Reactions Aliphatic and Alicyclic Chemistry Aromatic Compounds Heterocyclic Compounds Organometallic Chemistry (Transition Elements) Synthetic Methods and Enzyme Chemistry. The reader is referred to the Society’s bimonthly journal Natural Product Reports for authoritative reviews of the chemistry and biosynthesis of particular groups of natural products. We pick out below some of the advances which have particularly taken our interest in the reviews in Volume 93 – the selection is personal and does not claim to be representative.Radical allylations can be e§ected neatly using an aryl allyl sulfone the first example of a catalyst to promote enantioselective radical additions to electron-deficient dienes and the preparation of a C 2 -symmetric non-racemic tin hydride are amongst important advances in synthetic radical chemistry; the interested Reader should certainly consult the 1996 Organic Reactions chapter on radical chemistry. Reviews on the increasingly studied Combinatorial Chemistry together with signficant advances have featured this year. Many delightful examples of tandem/cascade processes allow the rapid construction of polycyclic systems of all types. In this context the organic synthetic chemist becomes ever more comfortable with metathesis processes – this year for example the tolerance of b-lactams to the reaction conditions and the use of metathesis processes to make crown ethers has been described.Aziridines can be produced from imines and diazo compounds or by aza-Darzens processes. Dimethyldioxirane is increasingly exploited in various oxidative procedures – much higher concentrations can be obtained using a procedure which generates solutions in chlorinated solvents. The problem presented by ring opening of 2-lithiooxazoles has been circumvented by using their borane complexes. Biocatalytic hydrolysis of Schi§ bases from racemic amino acid esters in the presence of a base to epimerise the nonhydrolysed enantiomer allowed nearly 90% conversion to one enantiomer of the amino acid; biocatalytic resolution of arylethanamines can be achieved by lipasemediated hydrolysis of their octyl oxalamic esters.Microwave irradiation increases the rate of enzyme-catalysed reactions. The enzyme-catalysed hydrolysis of phthalimides holds considerable promise as a very mild way to release amines from such protected forms. Royal Society of Chemistry–Annual Reports–Book B 1 It is becoming increasingly apparent that it is now possible to reliably model complex organic processes in solution by computational methods. Chapter 3 describes continued progress in the development of continuum models and of more explicit methods for the representation of solvent in computer simulations of organic reactions. The use of advanced computational methods to model the stability of host-guest complexes and the position of the equilibrium for a variety of complex organic reactions is also described. The use of laser flash photolysis in the generation of reactive intermediates of organic reactions have deprived these species of much of their mystery to the continuing benefit of mechanistic organic chemists. Chapter 4ii reviews methods for the generation of enols ynamines nitrenes and carbocations; and the results of structurereactivity studies on these species. 2 John A. Joule and John P. Richard