Rolf Huisgen, Some Roots of His Success. ± Rolf Huisgen was a student of Heinrich Wieland, one of the most prominent Organic Chemists of the first half of the 20th century. The Wieland school was famous in natural products chemistry, isolation and determination of the constitution of, e.g., steroids and alkaloids, and in synthesis. Rolf Huisgen, one of Wielands last students, worked on Strychnos alkaloids for his Ph.D.
The methodology of the time was still very classical: crystallization, distillation, and chemical-degradation procedures were the meager tools leading to success. Wieland did not only think in structures and synthesis, but also in reactivity. In a series of papers On the Occurrence of Free Radicals in Chemical Reactions, he established himself as one of the fathers of Free-Radical Chemistry [1]. Through his famous series of publications on Biological Oxidations [2], he became one of the founders of modern dynamic biochemistry, and, likewise, a precursor of modern mechanistic thinking in Organic Chemistry. The Wieland school, therefore, definitely was one of the important roots for Rolf Huisgens success on his way to mechanistic thinking, and he has expressed this with high esteem for his academic teacher on many occasions.
His prime interest in dynamics and reactivity as a key to a better understanding of Organic Chemistry can be recognized already in his first independent research on the angular vs. linear fusion of aromatic rings starting from b-substituted naphthalenes and quinolines [3]. Although basic mechanistic investigations of Hans Meerwein and others, as well as the initiation of MO theory by Erich Hückel, had set the path for modern Organic Chemistry in Germany before, and despite the comprehensive publication of the Grundlagen der theoretischen Organischen Chemie by Walter Hückel, modern mechanistic approaches had its breakthrough in Germany mainly due to Huisgens work, which, of course, was stimulated by the British and American systematic Physical Organic Chemistry approaches of Louis Hammett, Christopher Ingold, Paul Bartlett, Saul Winstein, and others.
The application of kinetics became a magic wand in Huisgens hands, and his review in Houben-Weyl [4] on kinetic methods became a bible for his students. Investigation of reaction mechanisms was for him, however, at no time an end in itself, but rather a tool to understand reactivity better for improving and expanding synthesis. By this typical Huisgen approach, he gained understanding of reactivities in larger areas of Organic Chemistry than, probably, any other researcher. He never followed fashion trends in chemistry, but he rather set new trends himself, e.g., in nitrogen chemistry, or