The synthesis of safranal

Introduction: Safranal is a cyclic monoterpene which occurs naturally in the saffron plant as a glucoside, picrocrocin. In 1922 Winterstein and TeleCzky obtained safranal by hydrolysis of picrocrocin, but its structure was not determined. Kuhn and Winterstein hydrolyzed picrocrocin in 1933 and obtained safranal and glucose in a one to one ratio. The structures for safranal and picrocrocin were determined. [illustration] Since this time there have been many attempts to devise a practical synthesis of safranal. Among these has been the work of Kuhn and Wendt, who obtained safranal in 1-3% yield by dehydrogenation of [beta]-cyclocitral. Karrer and Ochsner attempted its synthesis by bromination of [alpha]-cyclocitral with N-bromosuccinimide followed by dehydrobromination, but a rearrangement took place. Lunt and Sondheimer obtained a homolog of safranal, 4-methyl safranal, by a Diels-Alder type condensation. Other attempted syntheses have proven unsuccessful. This paper presents the results of attempts to synthesize safranal from the enol acetate of cyclocitral. It is a continuation of the work begun by Vittimberg in 1951. He succeeded in obtaining the enol acetate of cn good yield and determined its structure. Cyclocitral was prepared by first forming a Schiff base from citral (I) and aniline. This was cyclized with concentrated sulfuric acid and steam-distilled to give a mixture of [alpha]- and [beta]-cyclocitral (II and III) in a ratio of 2/3 to 1/3. This mixture was treated with a large excess of isopropenyl acetate to form the enol acetate of cyclocitral. Both [alpha]- and [beta]-cyclocitral give the same enol acetate (IV).

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

1953

Author dc:creator

• Nelson, David A. (David Alan), 1931-

Advisor dc:contributor.advisor

• George Büchi.

• Chemistry

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/60741

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/60741