Process for the preparation of bimatoprost

A compound of formula (III):

• wherein
• R1 is selected from the group consisting of (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl, —(CH2—CH2—O)n—CH3 wherein n=1, 2, 3 or 4, and —CH(O—CH2—CH2)2,
• R2 is selected from the group consisting of H, (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl,
• or, alternatively, R1 and R2 taken together are selected from the group consisting of —CH2—CH2—CH2—, —CH2—CH2—, —O—CH2—CH2—, and —O—CH═CH—.

A compound of formula (II)

• wherein
• R1 is selected from the group consisting of (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl, —(CH2—CH2—O)n—CH3 wherein n=1, 2, 3 or 4, and —CH(O—CH2—CH2)2,
• R2 is selected from the group consisting of H, (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl,
• or, alternatively, R1 and R2 taken together are selected from the group consisting of —CH2—CH2—, —O—CH2—CH2—, and —O—CH═CH—.

A process for the preparation of the compound of formula (II)

• the process comprising reacting a compound of formula (III):
• with ethylamine in the presence of a suitable solvent, wherein
• R1 is selected from the group consisting of (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl, —(CH2—CH2—O)n—CH3 wherein n=1, 2, 3 or 4, and —CH(O—CH2—CH2)2,
• R2 is selected from the group consisting of H, (C1-C16)alkyl, (C1-C16)haloalkyl, (C2-C16)alkenyl, (C2-C16)haloalkenyl, (C1-C16)alkoxy(C1-C16)alkyl, aryl, (C1-C16)alkylaryl, allyl,
• or, alternatively, R1 and R2 taken together are selected from the group consisting of —CH2—CH2—CH2—, —CH2—CH2—, —O—CH2—CH2—, and —O—CH═CH—.