5-(6-imidazo(1,2-a)-pyridyl)pyridine derivatives

#The present invention relates to novel 5-(6-imidazo[1,2-a]pyridyl)pyridine derivatives possessing excellent cardiotonic effect. More particularly, the present invention relates to novel 5-(6-imidazo[1,2-a]pyridyl)pyridine derivatives and pharmacologically acceptable salts thereof and a process for producing the same as well as pharmaceutical compositions comprising the same.

#A serious cause of congestive heart failures is the depressed contraction of the heart muscle. For treating such heart failures, digitalis preparations have been used heretofor. The digitalis preparations have already had a history for 200 years and have become almost a synonym for cardiotonics. However, the digitalis preparations are accompanied by the serious problems in that the toxic-to-therapeutic ratio is narrow and the therapeutic effect is also insufficient.

#Cardiotonics acting on sympathetic nerves such as isoprotenol, dopamine, dobutamine, etc. have also been widely used. However, these cardiotonics not only have side effects such as increase in heart rate and arrhythmogenicity etc., but also exhibit their effect only by an intravenous administration. Accordingly, these cardiotonics cannot be used for treating chronic congestive heart failures.

#Next, representative compounds of the present invention are given below but the present invention is not deemed to be limited thereto, needless to say.

#In 230 ml of N,N-dimethylformamide was dissolved 23.5 g of 4-dimethylamino-3-(imidazo[1,2-a]pyridin-6-yl)-3-buten-2-one. The solution was stirred at 80.degree. to 90.degree. C. for 12 hours, together with 9.48 g of .alpha.-cyanoacetamide and 12.2 g of sodium methoxide. After cooling, the solvent was removed by distillation under reduced pressure and 500 ml of water was added to the residue to dissolve it. The solution was washed with 600 ml of chloroform. Next, about 5 ml of acetic acid was added to the aqueous layer to adjust pH to 6.5. Crystals precipitated upon cooling were taken by filtration. After the crystals were washed with water, acetonitrile and then ether, they were dissolved in 200 ml of a 2.5% aqueous sodium hydroxide solution. The solution was treated with activated charcoal. The filtrate was again adjusted to pH of 6.5 with about 7 ml of acetic acid. Crystals precipitated upon cooling were taken by filtration. After the crystals were washed with water, acetonitrile and then ether, they were recrystallized from 100 ml of N,N-dimethylformamide to obtain 13 g of 1,2-dihydro-6-methyl-2-oxo-5-(imidazo[1,2-a]pyridin-6-yl)-3-pyridinecarbon itrile.

#Melting point: >300.degree. C.