Pergamon Tetrahedron 55 (1999) 1111-1118 TETRAHEDRON Reaction of Diimines and Benzyne Ashraf A. Aly, Nasr K. Mohamed, Alaa A. Hassan, AbouI-Fetouh E. Mourad Chemistry Department, Faculty of Science, EI-Minia University, EI-Minia, Egypt. Received 1 July 1998; revised 6 November 1998; accepted 19 November 1998 Abstract: The reaction between benzyne and the Schiff bases la,b and 15a,b leads to the 1,4-bis(2 L substituted acridin-10-yl)benzene 4a,b, the N-phenylarylamines 10a,b and the 10-(4 ~-formylphenyl)-substituted acridines 1la,b (from ta,b) and the 2-substituted acridine-10-carboxyaldehyde18a,b (from 15a,b). Cyclohexyl (4-cyclohexyliminomethylbenzyUdine)aminelc reacts with benzyne by an ene-reactionto give cyclohexenyl[(4- cyclohexyliminomethylphenyl)benzylidine]amine 14. © 1999 ElsevierScience Ltd. All rightsreserved. Introduction The Diels-Alder reaction has been of prime importance in organic synthesis for a long time 1-3, and among the numerous dienophiles employed arynes (dehydrobenzenes) have also been added to a variety of dienes4's. We are interested in preparing fused polycyclic compounds related to [2.2]paracyclophane using the Diels-Alder reaction s'7, especially the reactions which involve benzyne as a dienophile8. Because of the potential importance of the Diels-Alder reaction for the preparation of six-membered nitrogen heterocycles, we try to utilize this reaction with benzyne to synthesize such nitrogen heterocycles which have medicinal and industrial importance. Preparation of these compounds usually requires several steps and proceeds with relatively poor yields. The highly reactive parent system, benzyne, reacts with imines to give N-(o-anilinobenzhydryl)- aniline 9 and phenanthridine derivatives 1 o as well as acridines 11 via [2+2] and/or [4+2] cycloaddition reactions. Acridine derivatives have a wide range of applications in dye chemistry and are of medicinal importance as antitumor reagents 12,13. We have recently reported that cyclohexyl-(4-cyclohexyliminomethylbenzylidine)amine as well as N,N~-bis-(aryl)-benzene-l,4-diylidmethylidenediamines react with tetracyanoethylene ('l'CNE),l,4-benzo- and naphtho-quinone derivatives to give novel pyrrole, imidazolidine, quinoline, quinoxaline, indole and carbazole derivatives 14As. On the other hand, 3,4,5,6-tetrachloro-l,2-benzoquinone (o-CHL) provided a transient condensation product with the above diimines which underwent [4+2] cycloaddition 0040-4020/99/$ - see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0040-4020(98)01089-8