Isomerization of Styrene Oxide and Derivatives

This side-reaction can be suppressed by the use of zeolites, such as ZSM-5 (Si/ Al = 18.8), which hinder the formation of this aldol condensation and consecutive products because of the steric constraints of the framework. Lower temperatures lead to larger amounts of triphenylbenzene (7.6% at 200 °C compared with 

The gas-phase reactions of styrene oxide derivatives also gave very good results. 2-Methylstyrene oxide is, however, rearranged to a mixture of 2-phenylpro-panal and phenylacetone with selectivity of approx. 20% aldehyde and 60% ke- 

Fluoro- and chloro-substituted styrene epoxides can be converted to the corresponding substituted phenylacetaldehydes over ZSM-5 with selectivities of 90 % and higher [23]. These products are not obtainable via the Rosenmund reduction. 

Liquid-phase rearrangements of styrene oxides and their derivatives over zeolites in their H-form were deseribed by K. Smith et al. [24]. They obtained poor results with protic solvents such as methanol (30% conversion of styrene oxide). Use of chlorinated aprotic solvents sueh as dichloromethane led to higher yields of phenylacetaldehyde (74 % over H-ZSM-5 and 78 % over H-/8 at 20 °C, 

3 mmol styrene oxide, 0.5 g H-ZSM-5, 10 mL dichloromethane) but results were still inferior to those from the gas-phase reactions described above. 

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