TETRAHEDRON LETTERS Tetrahedron Letters 42 (2001) 6671–6674 Pergamon Efficient modified von Niementowski synthesis of novel derivatives of 5a,14b,15-triazabenzo[a ]indeno[1,2-c ]anthracen-5-one from indolo[1,2-c ]quinazoline Lisianne Domon, a Catherine Le Coeur, a Axelle Grelard, b Vale ´rie Thie ´ry a, * and Thierry Besson a, * a Laboratoire de Ge ´nie Prote ´ique et Cellulaire, EA3169, Groupe de Chimie Organique, U.F.R. Sciences Fondamentales et Sciences pour l’Inge ´nieur, Avenue Michel Cre ´peau, Universite ´ de La Rochelle, F -17042 La Rochelle cedex 1, France b Centre Commun d’Analyses, Universite ´ de La Rochelle, 5 Perspective de l’Oce ´an, F -17000 La Rochelle cedex 1, France Received 13 June 2001; revised 6 July 2001; accepted 25 July 2001 Abstract—Starting from 2-(2-aminophenyl)indole novel triazabenzo[a ]indeno[1,2-c ]anthracen-5-ones could be reached in three steps through a modified von Niementowski reaction, which involves condensation of anthranilic acids with an S -alkylated 6-mercaptoindolo[1,2-c ]quinazoline. Microwave irradiation in dry media was used in order to improve reactions where conven- tional heating was limited. © 2001 Published by Elsevier Science Ltd. For the last two decades, marine natural products have constituted an important source of inspiration for chemists and have received increasing attention as a source of new and useful pharmaceuticals and biologically active compounds. 1 Hinckdentine A (1) 2 is an unusual marine alkaloid which has a unique molecular skeleton consisting of a seven-membered lactam ring fused to a indolo[1,2-c ]quinazoline (2). This latest ring system is little known and its synthesis has been achieved in only a limited number of ways, mostly involving the use of 2-(2-aminophenyl)indole as starting material (Fig. 1). 2,3 In a search for new polyheterocyclic systems with potential pharmacological value, 4 we planned to prepare new polyheterocyclic compounds (3) from 2- (2-aminophenyl)indole and by fusing the indolo- [1,2-c ]quinazoline 2 and the quinazolin-4-one rings. This synthesis was performed via a modified Niemen- towski reaction 5 inspired by a recent work on the preparation of base-modified nucleosides by condensa- tion of anthranilic acid with a suitably protected sugar- derived 2-alkylthio-1,3-oxazoline. 6 In the course of our work on the use of microwaves in organic synthesis, 7 we confirm (last step) that exposi- tion of the reaction mixtures to microwaves gives strik- ing reductions in reaction times, good yields and Figure 1. Keywords : large ring heterocycles; Niementowski reaction; indolo[1,2-c ]quinazoline; microwave activation. * Corresponding authors. Fax: (33) (0)5 46 45 82 47; e-mail: vthiery@univ-lr.fr; tbesson@univ-lr.fr 0040-4039/01/$ - see front matter © 2001 Published by Elsevier Science Ltd. PII:S0040-4039(01)01364-8