Patent GB-1353370-A (GB)
Title: Imidazolpyridine derivatives
IPC: C07D471/04
Filed: 1971-09-13
Abstract: 1353370 Imidazo - pyridine derivatives MERCK & CO Inc 13 Sept 1971 [18 Sept 1970] 42581/71 Heading C2C Novel compounds of the Formula II: wherein R is a 5- or 6-membered monocyclic heteroaromatic ring containing from 1 to 3 hetero atoms that are oxygen, nitrogen or sulphur; or is 3-oxothiazol-4-yl, 3-oxothiazol-2- yl, cyano, amino, naphthyl, halonaphthyl, phenyl, halophenyl, biphenylyl or where X is oxygen or sulphur, R 2  is hydrogen or C 1-8  alkyl and R 3  is hydrogen, C 1-8  alkyl, C 3-10  cycloalkyl, C 1-8  alkylamino, di-(C 1-8  alkyl)- amino, alkylenimino, hetero interrupted alkyleneimino, C 1-8  alkoxy, C 1-8  alkylthio, C 6-12  aryl, aralkyl, heteroaryl, aryloxy, C 6-12  arylthio, heteroaryloxy, heteroarylthio, or an N-attached heterocycle; and R 1  is hydrogen, C 1-8  alkyl, C 1-8  alkoxy, C 1-8  alkylthio, phenyl, naphthyl, phenoxy, naphthyloxy, nitro, amino or where X, R 2  and R 3  are as previously defined, but with the proviso that when R is furyl, thienyl, naphthyl or phenyl, R 1  is other than hydrogen, may be prepared by: (1) for compounds II in which R 1  is limited to R 5  wherein R 5  is hydrogen, C 1-8  alkyl, C 1-8  alkoxy, C 1-8  alkylthio, phenyl, naphthyl, phenoxy, naphthyloxy, nitro or amino and R is limited to R 4  wherein R 4  is a five-membered monocyclic heteroaromatic ring containing from 1 to 3 hetero atoms that are oxygen, nitrogen or sulphur or is 3-oxothiazol-4-yl, 3-oxothiazol-2- yl, naphthyl, halonaphthyl, phenyl, or halophenyl by reaction of a compound 1A: with R 4 COCH 2 -hal, in which hal is a halogen atom; (2) for compounds II in which R 1  is limited to R 5  and R is limited to R 6 NH, where R 6  is R 3 -C(X)-, by acylation &c. of a free amino group at R; (3) for compounds in which R<SP>1</SP> is R 6 HN- and R is limited to R 8  wherein R 8  is a five-membered monocyclic heteroaromatic ring containing from 1 to 3 hetero atoms that are oxygen, nitrogen or sulphur or is 3-oxothiazol - 4 - yl, 3 - oxothiazol - 2 - yl, phenyl, naphthyl, halonaphthyl or halophenyl, by acylating &c. the corresponding compound in which R 1  is NH 2 ; (4) for compounds II in which R is limited to the 3-oxothiazolyls, by forming an N- oxide from a compound in which R is thiazolyl; (5) for compounds in which R 1  is limited to R 5  and R is NH 2 , treating a compound IVA with Hal-CH 2 .CONH 2  to yield a compound IVC: which is treated with a cyclizing solvent followed, if necessary, by hydrolysis to yield a compound II; (6) for compounds in which R 1  is limited to R 7 NH and R is limited to R 6 NH where R 6  and R 7  are the same or different or are R 3 -C(:X)-, by hydrolysing a compound VA to form an amino group at R, followed by acylation to form an R 3 -C(:X)- group at R, then reduction of nitro to amino and acylation of this amino to R 3 -C(:X)-; (7) for compounds in which R 1  is limited to R 5  and R is a 2-thiazolyl ring, contacting a 6-(R 5 )-2-alkoxy carbonylimidazo[1,2-a]pyridine with ammonia to form a carbamoyl group at the two position, converting this to cyano with phosphorus oxychloride, treating the cyano with hydrogen sulphide in basic media to form a thiocarbamoyl group which is cyclized with haloacetaldehyde to form the 2-thiazolyl ring. The intermediate 4-bromoacetylthiazole may be prepared by bromination of 4-acetylthiazole which is formed by treatment of 4-cyanothiazole with methyl magnesium iodide.