The Reaction of Arylidenemalonodinitriles with 1-Arylethylideneaminobenzenes. A New Synthesis of 5'-Amino-l,r:3',l"-terphenyl-2',6'-dicarbonitriles

The reaction of arylidenemalonodinitriles 1 with 1-arylethylidenemalonodinitriles 2 gives rise to sub­ stituted cyclohexadiene derivatives 3 which then undergo elimination of hydrogen cyanide and afford 3,5-diaryl-2,6-dicyano-aminobenzenes 4. This reac­ tion is a modification of more general dimerization reaction involving ylidenemalonodinitriles synthe­ sized from a variety of ketones. These typical di­ mers, easily obtained under basic conditions, have found limited applications due to difficult aromatization of a substituted cyclohexadiene system. The structure of “mixed dimers” 3 obtained from ylidenemalonodinitriles 1 and 2 facilitates aromatization of the cyclohexadiene system, and in fact the aromatization in some instances is so spontaneous that only o-aminonitriles 4 are isolated. The reac­ tion of ylidenemalonodinitriles 1 and 2 leading to o-aminonitriles 4 has been investigated by Gewald and Schill [1] and Sharanin et al. [2] and has been the subject of a recent review [3]. Recently, we discovered that heating of o-aminonitriles 4 in an autoclave in ethanolic sodium hydrox­ ide solution for several hours caused elimination of both cyano groups from 4 [4]. Aromatic amines 5 were obtained in most cases in excellent yields. The reaction of 1 and 2 leading to 4 although complex from mechanistic point of view, can be carried out in such manner that o-aminonitriles 4 are obtained in a simple step. Thus, 5'-amino-ra-terphenyls 5 and cer­ tain 3,5-diaryl-aminobenzenes are available by this strategy in essentially two steps from easily accessible synthetic precursors 1 and 2 (Scheme 1). We ex­ tended this synthetic approach to the preparation of some polyphenyl systems having m-diarylbenzene units [4], Synthesis of substituted ra-terphenyls received re­ cently renewed attention in connection with syn­ thetic routes leading to functionalized spherand sys­ tems [5]. Appropriately functionalized m-terphenyls are important building blocks for synthesis o f some spherands.