Crystalline forms of posaconazole intermediate and process for the preparation of amorphous posaconazole

A one pot process for the preparation of the amorphous form of 4-[4-[4-[4-[[(3R,5R)-5-(2,4-difluorophenyl)tetrahydro-5(1H-1,2,4-triazol-1-ylmethyl)-3-furanyl]methoxy]phenyl]-1-piperazinyl]phenyl]-2-[(1S,2S)-1-ethyl-2-hydroxypropyl]-2,4-dihydro-3H-1,2,4-triazol-3-one of the structural formula (IV), the process comprising:

• a) treating 4-(4-(4-(4-(((3R,5R)-5-((1H-1,2,4-triazol-1-yl)methyl)-5-(2,4-difluoro phenyl)tetrahydrofuran-3-yl)methoxy)phenyl)piperazin-1-yl)phenyl)-1-((2S,3 S)-2-(benzyloxy)pentan-3-yl)-1H-1,2,4-triazol-5(4H)-one of the structural formula (III) with concentrated hydrochloric acid and stirring the reaction mixture at an elevated temperature;
• b) cooling the reaction mixture and adding a halogenated hydrocarbon solvent;
• c) separating the layers;
• d) adding a halogenated hydrocarbon solvent to the aqueous layer and adjusting the pH to 8-12;
• e) partially concentrating the organic layer and optionally adding an aliphatic ketone solvent to the reaction mixture;
• f) mixing the reaction mixture of step e) and an aliphatic hydrocarbon solvent at a lower temperature;
• and
• g) filtering and optionally washing with aliphatic hydrocarbon solvent to provide amorphous compound of the structural formula IV.