Industrial synthesis of terpene compounds

Abstract

The translation of new organic syntheses carried out on a laboratory scale into plant practice is a problern 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 ehernist working in industry. The chemist's own knowledge of other scientitic 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 tonsjyear 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 exotherrnie 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 trichloride, 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 bemastered industrially, the reduction of triphenylphosphine oxide to triphenylphosphine being of great economic importance, to develop from suitable building blocks, mainly C 5 compounds having functional groups, such as CHO-C=CH-CH 2 -0H,

A convenient and mild chromatography-free method for the purification of the products of Wittig and Appel reactions

“…9 The BASF process for carotenoid synthesis 10 provides a good illustration of the issues. In it, the alkene product from a Wittig reaction is separated first from the bulk of the phosphine oxide by extraction 25 with hydrocarbon solvents, and then scrubbed of remaining oxide in a second extractive column with aqueous alcohol.…”

“…25 A recent report focuses on utilising the phosphine oxide by -product of the Wittig reaction as a catalyst or co-catalyst (produced in situ) in a subsequent step of a tandem reaction sequence, thus improving the atom economy of the overall process. 6 The conversion of 10 phosphine oxide to phosphine has also been realised by treatment with oxalyl chloride followed either by reaction of the resulting CPS (vide infra) with aluminium metal combined with a catalytic metal salt, 26 or by electrochemical reduction of the CPS. 27 15 Finally, we note that it is not uncommon that the method used to remove phosphine oxide may result in isomerisation of a Zalkene product of a Wittig reaction.…”

Wittig- and Horner–Wadsworth–Emmons-Olefination Reactions with Stabilised and Semi-Stabilised Phosphoranes and Phosphonates under Non-Classical Conditions

“…30 Previously, the use of hexane after acidification with sulfuric acid had been used to remove the alkene product from the triphenylphosphine oxide in the BASF carotenoid synthesis. 31,32 Wittig reactions have also been performed in micellar solutions of sodium dodecyl sulfate (SDS,20) in water between aldehydes and phosphoranes, prepared in situ (Scheme 6). 33 Wittig-Horner reactions in biphasic medium have been studied extensively.…”

Synthesis of a New C-15 Phosphorus Ylide Used for the Preparation of Some β-End-Group Retinoid Derivatives

“…This reaction, discovered by Wittig, was used in the BASF processes for vitamin A, b-carotene, and other carotenoid productions. [4][5][6] (Scheme 2 illustrates the last steps of vitamin A synthesis. )…”