Otto Billeter or How the Oldest [3,3]-Sigmatropic Rearrangement Went to Neuchâtel Otto Billeter oder wie die älteste [3,3]-sigmatrope Umlagerung nach Neuenburg kam: Teil1

Abstract

A historical study on the early chemistry of organic isothiocyanates (mustard oil) and thiocyanates (rhodanides) is presented. The isomeric structures of these compounds were settled by the famous investigations of August Wilhelm Hofmann published in 1868. Another highlight in this early phase of structural chemistry was the discovery by Otto Billeter and independently by Gustav Gerlich that allyl thiocyanate rearranges thermally into mustard oil (allyl isothiocyanate). This rearrangement can be regarded as the oldest [3,3]-sigmatropic process realized nearly 40 years before Ludwig Claisen started his well-known investigation on the thermal rearrangement of allyl phenyl ethers. The further development of the chemistry of thiocyanates and isothiocyanates will be discussed in the second part of this study.