US 7,521,545 B2
Azo compounds and process for production thereof
Tomomi Ikemoto, Osaka (Japan); and Takeshi Yamasaki, Osaka (Japan)
Assigned to Takeda Pharmaceutical Company Limited, Osaka (Japan)
Appl. No. 11/661,183
PCT Filed Aug. 25, 2005, PCT No. PCT/JP2005/015390
§ 371(c)(1), (2), (4) Date Feb. 26, 2007,
PCT Pub. No. WO2006/022311, PCT Pub. Date Mar. 02, 2006.
Claims priority of application No. 2004-248217 (JP), filed on Aug. 27, 2004.
Prior Publication US 2008/0009539 A1, Jan. 10, 2008
Int. Cl. C07D 307/79 (2006.01); C07D 405/04 (2006.01)
U.S. Cl. 534—581  [534/787; 548/454] 7 Claims
 
1. A process for producing an aromatic azo compound represented by the formula (III):

OG Complex Work Unit Drawing
wherein the A ring is a benzene ring that has at least one electron-withdrawing group in addition to the diazonium group and may be further substituted; R1 and R2 are the same or different and are each independently C1-6 alkyl; R3 is optionally substituted aryl; and R4, R5 and R6 are the same or different and are each independently hydrogen atom, C1-6 alkyl, halogen, C1-6 alkoxy or C1-6 alkylthio, or a salt thereof, which comprises subjecting a benzenediazonium salt represented by the formula (I):

OG Complex Work Unit Drawing
wherein the A ring is as defined above, and a compound represented by the formula (II):

OG Complex Work Unit Drawing
wherein R1 to R6 are as defined above; and X− is an anion, or a salt thereof, to diazo coupling in a mixed solvent substantially consisting of water and an organic solvent (other than carboxylic acid solvents).