Process for Preparing Benzodiazepines

A process for producing a compound which is a benzodiazepine derivative of formula: (I) wherein: represents or R1 represents C1-6 alkyl, aryl or heteroaryl; each R3 is the same or different and represents halogen, hydroxy, C1-6 alkyl, C1-6 alkoxy, C1-6 alkylthio, C1-6 haloalkyl, C1-6 haloalkoxy, amino, mono(C1-6 alkyl)amino, di(C1-6 alkyl)amino, nitro, cyano, -CO2R', -CONR'R'', -NH-CO-R', -S(O)R', -S(O)2R', -NH-S(O)2R', -S(O)NR'R'' or -S(O)2NR'R'', wherein each R' and R'' is the same or different and represents hydrogen or C1-6 alkyl; n is from 0 to 3; X represents -NH-, -N(C1-C6alkyl)-, -CO-, -CO-NR'-, -S(O)- or -S(O)2-, wherein R' is hydrogen or a C1-C6 alkyl group; and R4 represents hydrogen; or -CO-R4' or -CO-NH-R4 ', wherein R4 ' is a C1-C6 alkyl, C1-C6 hydroxyalkyl, aryl, heteroaryl, carbocyclyl or heterocyclyl group, which group is substituted by a C1-C6 hydroxyalkyl, aryl, heteroaryl, carbocyclyl or heterocyclyl group or a -(C1-C4 alkyl)-X1-(C1-C4 alkyl)-X2-(C1-C4 alkyl) group, wherein X1 represents -O-, -S- or -NR'-, wherein R' represents H or a C1-C4 alkyl group and X2 represents -CO-, -SO- or -SO2-; or R4 'represents -A1-Y-A2, wherein: A1 is an aryl, heteroaryl, carbocyclyl or heterocyclyl group; Y represents a direct bond or a C1-C4 alkylene, -SO2-, -CO-, -O-, -S or -NR'-, wherein R' is a C1-C6 alkyl group; and A2 is an aryl, heteroaryl, carbocyclyl or heterocyclyl group; or R4 is a group selected from aryl-C(O)-C(O)-, heteroaryl-C(O)-C(O)-, carbocyclyl-C(O)-C(O)-, heterocyclyl-C(O)-C(O)- and -ZR5, wherein: Z represents -CO-, -S(O)- or -S(O)2'; and R5 represents C1-6 alkyl, hydroxy, C1-6 alkoxy, C1-6 alkylthio, aryl, heteroaryl, carbocyclyl, heterocyclyl, aryl-(C1-6 alkyl)-, heteroaryl-(C1-6 alkyl)-, carbocyclyl-(C1-6 alkyl)-, heterocyclyl-(C1-6 alkyl)-, aryl-(C1-6 alkyl)-O-, heteroaryl-(C1-6 alkyl)-O-, carbocyclyl-(C1-6 alkyl)-O-, heterocyclyl-(C1-6 alkyl)-O- or -NR'R'' wherein each R' and R'' is the same or different and represents hydrogen, C1-6 alkyl, carbocyclyl, heterocyclyl, aryl, heteroaryl, aryl-(C1-6 alkyl)-, heteroaryl-(C1-6 alkyl)-, carbocyclyl-(C1-6 alkyl)- or heterocyclyl-(C1-6 alkyl)-; or a pharmaceutically acceptable salt thereof; which process comprises: (a) subjecting a racemic benzodiazepine derivative of formula: (IIa): wherein R1, R3, R4, n and X are as defined above, and R2 represents an amino protecting group, to crystallisation induced dynamic resolution to yield a benzodiazepine derivative of formula (II): wherein, R1,