Imine Hydrogenation Laboratory Process

The preparation of the three MEA enamides proved to be rather difficult. Disappointingly, we did not succeed in hydrogenating any of the three isomers using seven different Rh-diphosphine complexes at normal pressure and temperatures up to 50 °C. 

The hydrogenation of methoxyacetone was somewhat more successful using a Pt/C catalyst modified with cinchonidine as described by Orito et al. [5] (R)-meth-oxyisopropanol was obtained in good yields, but the ee values were never higher than 12%. 

This was not tested experimentally, because chances for success were considered to be too low. 

The results of the route screening left the hydrogenation of the MEA imine as the only realistic possibility. 

---

After intensive development work, first in the laboratory (conqjrising >1500 ejq)eriments) and later in the pilot plant (also used for the production of the first commercial quantities), the following production process was established in early 1978 (see Figure 3) MOIP is dehydrogenated in the gas phase and MOA is isolated by azeotropic distillation vrith water. The MEA imine formed in situ fi-om MOA and MEA is hydrogenated in a batch process at 5 bar... 

---