A.A. Philippov, A.M. Chibiryaev
Non-catalytic Meerwein—Ponndorf—Verley—Oppenauer Type Reaction of Monoterpenoids in Supercritical Fluids
Catalyst-free Meerwein—Ponndorf—Verley—Oppenauer reaction was studied for
cyclic monoterpenic ketones and alcohols (menthone, camphor, menthol and borneol)
under supercritical conditions. It is shown that ketones can be reducedin supercritical
isopropanol with high selectivity (89—98 %) under catalyst- and base-free conditions.
Conversion of menthone and camphor achieves 63 % (at 350 °C) and 11 % (at 300 °C),
correspondingly, for 5 hours. In reversed «dehydrogenation» of menthol and borneol
in sc-acetone, conversion reaches 34 % and 22 %, respectively, while selectivity is 95%
and 88 %. In all cases the main side reaction was the thermal dehydrationof alcohols.
Key words: supercriticalfluids, monoterpenic ketones, monoterpenic alcohols, hydrogen transfer reaction