Industrial synthesis of terpene compounds

Abstract

The translation of new organic syntheses carried out on a laboratory scale into plant practice is a problem which is as old as industrial chemistry itself. The worldwide growth of chemistry necessitates today the production of, inter alia, compounds of complex structure on a scale which has hitherto been reserved for commercial syntheses. This has placed great demands on the chemist working in industry. The chemist’s own knowledge of other scientific disciplines and his working together with physicists and engineers as a team are essential pre-requisites for economic success. The problems arising in connection with the scaling up of new reactions into chemical processes, say, for the production of 1000 tons/year of a vitamin will be described in more detail, referring to a few examples which, for the sake of simplicity, will be restricted to problems in terpene chemistry. The reaction discovered by Wittig in the ’fifties and named after him, namely the introduction of a double bond using phosphoranes, will be explained with reference to the syntheses of vitamin A, carotenoids and terpenes. With the aid of a flow sheet it will be shown how the problems occurring in the translation of these strongly exothermic reactions into industrial processes can be solved without taking risks, how triphenylphosphine which is required for the Wittig reaction can be safely produced on a commercial scale from phosphorus tri-chloride, sodium and chlorobenzene and how the triphenylphosphine oxide formed in the Wittig reaction can be reconverted into triphenylphosphine. It is possible with these basic reactions which can be mastered industrially, the reduction of triphenylphosphine oxide to triphenylphosphine being of great economic importance, to develop from suitable building blocks, mainly C5 compounds having functional groups, such as [formula omitted] or from methyl heptenone a large number of hitherto difficultly accessible terpenoids, such as heptaminol, hydroxycitronellal, citral, menthol, pear ester, lavandulol, juvenile hormone, sinensal, ionones and irones. Examples of the industrial synthesis of methylheptenone from acetone, formaldehyde and isobutylene and of isoprene will also be given. © 1975, Walter de Gruyter. All rights reserved.