Studies on alkyl‐substituted, heteroaromatic carbonitriles: Novel synthesis of thienoazines and benzoazines

Abstract

Abstract The alkyl‐substituted heterocyclic carbonitriles 1 – 3 react with elemental sulphur to yield the thienoazines 7 , 11 and 13 , respectively. Whereas 7 reacts with acrylonitrile to afford a [4+2] cycloaddition product with elimination of hydrogen sulphide, compounds 11 and 13 are not converted into cycloadducts. The quinoline 9a and the quinazoline 14 are obtained by reaction of 1 and 3 , respectively, with formaldehyde and malononitrile. The thienopyridines 16 are produced by reaction of 6a , c with benzylidinemalonitrile. Furo[3,4‐ f ]indazole 19 is prepared by [4 + 2] cycloaddition of the thienopyrazole 18 with maleic anhydride. The effect of the substituent of the thienyl moiety of the thienopyridazine ring system on its reactivity toward electron‐poor olefins has been investigated.