Process for preparing quetiapine and quetiapine fumarate

The invention comprises a process for preparing quetiapine and/or its salts, including, quetiapine fumarate. The process generally comprises reacting dibenzothiazepinone (dibenzo[bf][1,4]thiazepin-11(10H)-one) with phosphorous oxychloride in the presence of triethylamine in an aromatic organic solvent such as toluene or, preferably, xylene at reflux temperature to obtain an aromatic hydrocarbon solution of 11-chloro-dibenzo[bf][1,4]thiazepine. Thereafter, the 11-chloro-dibenzo[bf][1,4]thiazepine is reacted with 2-(2-piperazin-1-ylethoxy)-ethanol to yield, following several processing steps, quetiapine. Compound I can then be further reacted with fumaric acid at elevated temperature to yield quetiapine fumarate. The resulting quetiapine fumarate obtained is suitable for use in pharmaceutical preparations.