Pyrimido[4,5-b]indoles, fused tricyclic 6:5:6 compounds with three nitrogen atoms (2:1:0; positions 1, 3, and 9, and bicyclic 5:6 analogues, pyrrolo[2,3-d]pyrimidines), are of interest because of their extensive use as active ingredi-ents of pharmaceutical preparations.[1,2] Recently some of these compounds have been reported as useful new drugs in treatment of myocardial injury, pulmonary hyperten-sion, renal failure, Huntington’s chorea, as well as neuro-degenerative disorders such as Parkinson’s disease, Alzheimer’s disease and focal ischemia.[2] So far, several synthetic methods have been reported for the preparation of pyrimido[4,5-b]indole ring systems. The most common synthetic routes involve ring closure of 2,3 functionalized indoles, e.g. 2-aminoindole-3-carboxylates or 2-aminoindole-3- carbonitriles with CN atom fragments such as formamide or cyanamide.[2,3] In this study we have reported a new methode for the synthesis of five novel of 2-substitueted-4,9-dimethyl- 9H-pyrimido[4,5-b]indole (3a-e) catalyzed by Pd(0) wherein the biologically active indole moiety is fused to a potent pyrimidine ring across the 4, -positions (Scheme 1).

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