Professor Charles Rees

Groundbreaking organic chemist

Charles Wayne Rees, chemist: born 15 October 1927; Lecturer in Organic Chemistry, Birkbeck College, London University 1955-57; Lecturer in Organic Chemistry, King's College London 1957-63, Reader 1963-65; Professor of Organic Chemistry, Leicester University 1965-69; Professor of Organic Chemistry, Liverpool University 1969-77, Heath Harrison Professor of Organic Chemistry 1977-78; FRS 1974; Hofmann Professor of Organic Chemistry, Imperial College, London 1978-93 (Emeritus); CBE 1995; married 1953 Patricia Francis (three sons); died London 21 September 2006.

Charles Rees was one of the most eminent organic chemists of his generation. He specialised in the area of heterocyclic chemistry - the study of rings made up of carbon, nitrogen, oxygen and sulphur atoms - a subject that touches all of our daily lives. Many medicinal drugs, textile dyes and reprographic materials, as well as a very large number of naturally occurring compounds, including the DNA bases, the building blocks of life itself, are heterocyclic molecules.

Heterocyclic chemistry is a vast subject that because of its immense importance has attracted many scientists over the years. Occasionally one comes across a person whose total grasp of the subject, flair and ability to translate completely new ideas into practice, makes him stand out above others. Charles Rees was such a person.

Rees was born in 1927 in Egypt, where his father was serving in the British army. After Farnham Grammar School, he spent three years as a laboratory technician at the Royal Aircraft Establishment, Farnborough, in Surrey, before going to University College, Southampton (later Southampton University). After graduating in 1950, he remained in Southampton to undertake research with Professor N.B. Chapman, studying the chemical reactions of heterocyclic compounds, and obtained his PhD in 1953, the same year he married Patricia Francis.

Following a postdoctoral period at the Australian National University, then located in the Euston Road, London, working on antibacterial compounds, Rees was appointed assistant lecturer at Birkbeck College, London, in 1955, thereby initiating his 50-year independent research career.

After two years at Birkbeck, Rees moved to King's College London, where he spent a productive eight years, being promoted to Reader in 1964. During this period, the organic chemistry section at King's, under the leadership of the Daniell Professor, Donald Hey, was a formidable group, many of whom were subsequently appointed to chairs elsewhere and elected to the Royal Society.

Rees's research in heterocyclic chemistry blossomed at King's, and culminated in the 1965 "Chemical Communications" paper describing his brilliantly conceived oxidation of a heterocyclic amine causing it to lose nitrogen gas whilst simultaneously generating the highly reactive species benzyne (C6H4). This methodology was ingeniously extended to other reactive species, and remains one of Rees's major contributions to chemistry.

In 1965, Rees was appointed to the chair of Organic Chemistry at Leicester University, where he continued his seminal studies on nitrogen-containing heterocycles. A highlight of this period was the generation, for the first time, of a reactive, so-called antiaromatic, three-membered ring nitrogen compound. Aromatic compounds such as benzene are stable, widespread and well known, but their antiaromatic counterparts are unstable and short lived, requiring special methods for their formation.

The stay in Leicester was relatively short, and in 1969 Rees moved to the chair of Organic Chemistry in Liverpool, where he stayed almost 10 years. During this period, he continued his exploration of the chemistry of unusual ring structures, and was the first person to access the elusive azacyclobutadiene ring system. This is another highly reactive, antiaromatic ring compound whose structure was of great interest to theoreticians at the time. Rees was able to isolate the ring system at low temperature and intercept it in chemical reactions. In 1974 Rees's contributions to chemistry were recognised by his election to the Royal Society.

In 1978, Rees succeeded the Nobel Laureate Sir Derek Barton to the Hofmann Chair of Organic Chemistry at Imperial College, London, where he remained until his retirement in 1993. His research at Imperial College was characterised by two major contributions, the use of reactive species to synthesise biologically important molecules, and his investigations into new aromatic compounds. In the first area, he developed general procedures for the preparation of a range of heterocyclic systems, in particular the indole ring, an important constituent of many natural products, neurotransmitters and synthetic drugs.

However, it was Rees's love of new ring systems that defined his work in the latter part of his career. This is reflected in the discovery of two entirely new classes of aromatic compounds. The first, the tricyclic [10]-annulenes, were discovered in Liverpool but much of their chemistry was developed in London. These theoretically interesting molecules are stable aromatic structures that added greatly to our knowledge of this fundamental class of compounds.

Secondly there is the ground- breaking work on heterocyclic systems that are rich in sulphur and nitrogen atoms. This work, from its beginning in the early 1980s, has uncovered a number of totally new heterocyclic ring systems, with Rees succeeding in bringing a fresh new approach to an exciting area of heterocyclic chemistry.

Rees's contributions were recognised by honorary doctorates and a number of awards, including the Royal Society of Chemistry Tilden and Pedler Lectureships, the (first) Royal Society of Chemistry Award in Heterocyclic Chemistry in 1980 and the International Award in Heterocyclic Chemistry in 1995. He was appointed CBE in 1995.

Rees was more than just a distinguished researcher. He was generous with his time and served the scientific community in many ways: he was President of the Royal Society of Chemistry for two years from 1992, also serving on its Council; President of the Organic Chemistry Division of the RSC; and President of the Chemistry Section of the British Association for the Advancement of Science. In addition, he co-edited three leading reference works, Comprehensive Heterocyclic Chemistry I & II (1984-96), and Comprehensive Organic Functional Group Transformations (1995).

Charles Rees had enormous charm. He was a great raconteur with a razor-sharp wit. Nobody who attended a scientific conference at which he delivered the after-dinner address will ever forget him.

Christopher J. Moody