Date of Award
Master of Science in Chemical Engineering - (M.S.)
James A. Bradley
Chemical literature abounds with methods for the synthesis of Indole and its derivatives. Undoubtedly, this is so, because Indole is the parent substance of the historical dyestuff Indigo. This coloring material has been the subject of extensive investigations for many centuries. Early in this century, importance was still placed on Indole Chemistry, but it later gore way to other dyestuffs having different chemical structures. It seems, however, the loss in popularity was to have been short-lived, because of the revitalized interest shown in the chemistry of Indoles since the early 1930's.
It was found that a great number of alkaloids were also derivatives of the Indole nucleus and hence, could enter into a great many syntheses. The amino acid Tryptophan, which has been found to be extremely important to animal nutrition is a derivative of Indole -- as are also many plant hormones.
We also find Indole being used in the perfume industry to enhance such delicate floral imitations as gardenia, lilac and jasmin.
With this very brief introduction to Indole, we will next consider a synthesis of this important substance and still more important intermediate, although the true pleasure lies in being first to synthesize a compound, it would indeed be folly to even imagine being first to try a synthesis of Indole. The author was naive enough earlier in this investigation to think a new approach was at band; however, a few hours with the literature cast a new and revealing light on the multitude and variety of synthesis already labored over.
The synthesis first to be investigated in this paper is that using O-amino phenyl-ethyl alcohol as the starting material. By first effecting a dehydration cyclization and then a dehydrogenation of the resulting 2,3- dihydroindole, the desired product is formed. A German patent 606,027 dated November 23, 1934 covers a similar investigation - details of which will be given later.
A second synthesis using 2-Hydroxy ethyl aniline and following the same procedure of cyclization by dehydration, then dehydrogenation, is also the subject of the present investigation, but to a much lesser degree than the first method. Unsuccessful attempts in synthesizing the 2-chloro ethyl aniline impeded any progress that might have resulted from this line of investigation.
In conclusion it might be added, that the present revitalized interest in the chemistry of Indoles, served to give the author sufficient impetus to conduct this minor investigation in what might otherwise be considered a fairly well exhausted topic of chemistry.
Scala, Stephen, "A study of a synthesis of indole" (1954). Theses. 2274.