It is difficult to pinpoint the exact starting point of organic chemistry, but undoubtedly
heterocycles belonged to the players of the first hour. Going back to the beginning
of the 19th century, a hallmark discovery can be placed to 1818—almost exactly 200 years ago—with
the isolation of alloxan (Figure [1]) from uric acid by Luigi Valentino Brugnatelli. Approximately 20 years later, Döbereiner
discovered furfural while distilling ants to produce formic acid. The ant bodies probably
contained some plant material which served as its source, and indeed, the production
of furans from pentoses and hexoses has developed today into one of the most important
processes for the utilization of renewable resources as fine chemicals or biofuels.
In the following two centuries, a seemingly endless variety of heterocycles has been
produced: approximately 25 million compounds are known to date, being ubiquitous in
natural products, drugs and materials.
Figure 1
The question might therefore arise if synthetic heterocyclic chemistry is a ‘mature’—a
nicer word for saying ‘old’—science, and whether advances that can be expected in
the future will be only found in the application of heterocyclic compounds in various
fields? Indeed, for many privileged heterocyclic scaffolds, reliable synthetic approaches
were discovered a long time ago, such as the [3+2]-Huisgen cycloaddition, the [2+2]-Paterno–Büchi
reaction, the Fischer indole, Friedländer, Bischler–Napieralski isoquinoline, and
the Paal–Knorr syntheses to name but a few, which are on par with synthetic methodology
in the 21st century. Nevertheless, the need to construct heterocycles in an atom- and step-economic
manner to tackle complex architectures found in Nature or being applied in smart materials
has greatly advanced the field of synthetic organic chemistry. Emerging technologies
and methods such as flow chemistry, C–H-activation, organocatalysis and visible light
photocatalysis often find early applications in conjunction with heterocyclic chemistry.
Stereoselective synthesis and catalysis would not be possible without the aid of heterocyclic
auxiliaries, directing groups or ligands. Arguably, heterocyclic chemistry is the
major driving force for these developments.
This Cluster on heterocycles is a joint effort between Synlett and the International Society for Heterocyclic Chemistry (ISHC, http://www.ishc-web.org),
which is celebrating its 50th anniversary this year. The 15 articles and accounts reflect some of the exciting
developments in heterocyclic chemistry that will be presented at ISHC 26, being held
in Regensburg from September 3–8, 2017. Almost 70 plenary, invited and oral contributions
along with 290 posters will impressively demonstrate the vibrant field of heterocyclic
chemistry. I am especially excited that the ISHC 2017 awardees: Prof. Yasuyuki Kita
(Ritsumeikan University, Japan), winner of the E. C. Taylor Senior Award, and Prof.
Chris Vanderwal (UC Irvine, USA), winner of the A. R. Katritzky Junior Award, have
contributed their latest results in an account and an article. Renowned speakers of
ISHC 25, which was held in 2015 in St. Barbara, USA, complement the contributions
of the current speakers.
I would like to express my gratitude to Thieme, a long-standing supporter of the ISHC
conference.
Prof. Dr. Oliver Reiser
University of Regensburg
President ISHC
