| CPC C07D 471/04 (2013.01) | 11 Claims |
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1. A process for preparation of a compound of formula (1) or a salt thereof,
![]() the process comprising:
(a) reacting in a solvent mixture comprising methanol and butanol, a compound of formula (3) and a compound of formula (4) to provide a compound of formula (2),
![]() and
(b) transforming the compound of formula (2) into the compound of formula (1) or a salt thereof.
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