Process for preparing substituted benzimidazole compounds
The invention relates to new methods of preparing substituted benzimidazole compounds, such as 2-bromo-5,6-dichlorobenzimidazole, which are useful in the preparation of compounds having antiviral activity.
1. A process for preparing a compound of formula VI:
wherein:
R is halo;
R 1 is hydrogen; and
each of R 2 , R 3 , R 4 , R 5 , R 6 and R 7 is independently selected from the group consisting of H, hydroxy and protected hydroxy group;
said process comprising the steps of:
(a) cyclizing 4,5-dichloro-o-phenylenediamine with carbonyl di-imidazole to yield a compound of formula II:
(b) reacting the compound of formula II with PO(X) 3 wherein X is halo, to prepare a compound of formula I:
and
(c) reacting the compound of formula I with a pyranoside of formula IV:
to prepare a compound of formula VI.
2. The process according to claim 1 , wherein said pyranoside of formula IV is a beta-D pyranoside; R 2 , R 4 , and R 6 are each hydroxy or O-acetyl; R 3 , R 5 , and R 7 are each H; and X and R are Br.