2-Triazolylpyrimido[1,2,3-cd]purine-8,10-diones via 1,3-dipolar cycloadditions to 2-ethynylpyrimido[1,2,3-cd]purine-8,10-dione

Article abstract of DOI:10.1002/jhet.5570370502

This paper presents the synthesis of a series of 5,6-dihydro-4H,8H-pyrimido[1,2,3-cd]purine-8,10(9H)-dione ring system derivatives with a [1,2,3]triazole ring bonded in position 2. The procedure is based on cycloaddition of substituted alkyl azides to the terminal triple bond of 5,6-dihydro-2-ethynyl9-methyl-4H,8H-pyrimido[1,2,3-cd]purine-8,10(9H)-dione (4). This cycloaddition produced two regioisomers - 5,6-dihydro-9-methyl-2-(1-substituted-1H-[1,2,3]triazol-5-yl)-4H,8H-pyrimido[ 1,2,3-cd]purine-8,10(9H)-dione (7) and 2-(1-substituted-1H-[1,2,3]triazol-4-yl) derivative 8. The required 2-ethynyl derivative 4 was obtained from the starting 2-unsubstituted compound 1 by bromination to yield the 2-bromo derivative 2, which was converted by Sonogashira reaction to trimethylsilylethyne 3 and finally, the protective trimethylsilyl group was removed by hydrolysis.