Amino-thienopyrazoles and Amino-thienopyrroles

Article abstract of DOI:10.1002/prac.199533701101

The synthesis of thieno<2,3-c>pyrazoles and thieno<2,3-b>pyrroles is described.From the dithioliumsalt (1) and potassium hydroxide the potassium-(2,2-dicyan-1-methylthioethen-1-yl)-thiolate (2) is formed.This reacts with hydrazine hydrate to form the 3-amino-5-thioxo-pyrazol-4-carbonitrile (3).S-alkylation with α-chlorocarbonyl compounds yielding (6a-c) leads via Thorpe-Ziegler-cyclization to 3,4-diaminothieno<2,3-c>pyrazoles (9) if the position 1 is alkylated (8).Acetyl acetone yields 2-mercapto-pyrazolo<1,5-a>pyrimidine (5).After S-alkylation (10a-d) are immediately cyclized to thieno <2',3':3,4>pyrazolo<1,5-a>pyrimidine (11a-d).The ketone (6a) can be cyclized to the pyrazolo <5,1-b>thiazole (12). 3 reacts with oxalyl chloride to form the 2,3-dioxo-6-thioxo-imidazo<1,2-b>pyrazole (13) of which S-phenacyl derivative (14) because the NH-proton cannot be cyclized.The 5-amino-3,4-dicyano-pyrrol-2-thiolate (16) shows the analogous behaviour.The S-alkylation is followed by cyclization, and 3,5-diamino-thieno<2,3-b>pyrroles (18a-b) arise.Reaction of 5-amino-2-alkylthio-pyrrol-3,5-dicarbonitrile (17) with acetyl acetone provides pyrrolo<1,2-a>pyrimidine (20a-c) which can be cyclized to form thieno<3',2':4,6>pyrimidines (21a-c) very easily.