(Chief Bee)
03-02-04 15:19
No 492479
(Rated as: excellent)
This article essentially show the reaction pathways to end up with propenylbenzene epoxide (a.k.a. 1-phenyl-1,2-epoxypropane or beta-methylstyrene oxide) regardless if the starting material available is 1-phenyl-1-propanone (P1P, propiophenone), or any 1-phenyl-1,2-halohydrin. The latter compounds can for example be formed by:
a) addition of an aqueous halogen solution to propenylbenzene,
b) addition of a halogen across that same double bond followed by hydrolysis
c) reduction of an alpha-halo-propiophenone, which in turn is obtained from propiophenone itself
The article uses some exotic biochemical methods to arrive at chiral epoxides, but if your final goal with the epoxide is to isomerize it to P2P it doesn't matter which epoxide isomer you start with, the end result is the achiral P2P anyway. This opens up for a lot of other cheap reducing agents instead of the enzymes used by this research group - examples include sodium borohydride and catalytic transfer hydrogenation with Pd/C and formic acid (and possibly even Zn/HCOOH).
Naturally, there are no specific limitations on this procedure to prevent this synthetic route from being used on other similar substrates, for example to produce MDP2P from 3,4-MD-Propiophenone or isosafrole.
Chemoenzymatic Synthesis of Chiral Epoxides.
Preparation of 4-Phenyl-2,3-epoxybutane and 1-Phenyl-1,2-epoxypropane.
Pascale Besse, Michel F. Renard and Henri Veschambre
Tetrahedron Assymmetry 5(7), 1249-1268 (1994) (../rhodium/pdf /ketone2chira
Abstract
All the stereoisomers of 4-phenyl-2,3-epoxybutane and 1-phenyl-1,2-epoxypropane (beta-methylstyrene oxide) have been prepared in three steps from 4-phenyl-2-butanone and 1-phenyl-2-propanone or 1-phenyl-1-propanone respectively, The key step is the microbiological reduction of the corresponding haloketones. These results confirm those previously described1 and demonstrate that the chemoenzymatic synthesis of homochiral 2,3-epoxides is a general method that can be used whatever the starting ketone.
The Hive - Clandestine Chemists Without Borders
