Process for preparing an intermediate for CNS depressants

A process for preparing (4a,13b-trans)-1,2,4,4a,8,9,13b,14-octahydro-3H-benzo[6,7]cyclohepta[1,2,3 -de]pyrido[2,1-a]isoquinolin-3-one, comprising:

• a. oxidizing 1,7,8,12b-tetrahydrobenzo[1,2]cyclohepta[3,4,5-de]-isoquinoline with a peracid oxidizing agent to obtain 1,7,8,12b-tetrahydrobenzo[1,2]cyclohepta[3,4,5-de]isoquinoline N-oxide;
• b. reacting the last-named compound with a haloolefin of formula ##STR7## in which X is chloro, bromo or iodo to obtain the corresponding quaternary salt of formula 4 ##STR8## in which X is the same as the halogen of the haloolefin employed;
• c. reducing the compound of formula 4 in which X is chloro, bromo or iodo with a complex metal hydride reducing agent to obtain (4a,13b-trans)-2,3,4,4a,8,9,13b,14-octahydro-1H-benzo[6,7]isoquinolin-3-ol ;
• and
• d. oxidizing the last-named compound with a reagent for converting a hydroxy function to the corresponding keto function to obtain (4a,13b-trans)-1,2,4,4a,8,9,13b,14-octahydro-3H-benzo[6,7]cyclohepta[1,2,3 -de]pyrido[2,1-a]isoquinolin-3-one.