3,4-Diacetylhexane-2,5-dione - An effective synthon for synthesis of substituted azulene heteroanalogs by cyclocondensation reactions

Article abstract of DOI:10.1007/BF02495609

The one-pot method for the synthesis of 4,8-dialkoxy-6-aryl-1,3-dimethylcyclohepta[c]furanium perchlorates has been developed. The method is based on the cyclocondensation of 3,4-diacetylhexane-2,5-diones with aromatic aldehydes and trialkyl orthoformates under the action of a 16% perchloric acid solution in acetic anhydride. Under similar conditions, with hydrogen sulfide, cyclohepta[c]thiophenium perchlorates have been obtained, while cyclohepta[c]pyrrolium perchlorates have been prepared with arylamines, ammonium acetate, or aliphatic amine acetates. A heteroanalog of azulene, 4,8-diethoxy-1,3-dimethyl-2-azaazulene, has been obtained for the first time. Hydrolysis of aza- and thiaazulenium salts gives the corresponding cyclohepta[c]pyrrol-4-ones and cyclohepta[c]thiophen-4-ones.