Synthesis of Novel Oxazolo(4,5-a)carbazoles

Carbazole derivatives [1-6] have been reported to exhibit pharmacological properties like anti­ tumour, anticonvalsant, psychotropic, antiinflam­ matory, antihistamine and antibiotic properties. Oxazole derivatives [7-15] have been used as optical whitening agents, sensitizing dyes, photoreducing pigments, muscle relaxant and effective against wide range of enteric infections, appetite depressants. In the above contest our present investigation was aimed at to prepare hitherto un­ known oxazolo(4,5-a)carbazole derivatives 2 a -e from the corresponding 1-hydroxyimino-l,2,3,4tetrahydrocarbazoles l a e [6] in a single step with acetyl chloride at room temperature. l-Hydroxyimino-8-methyl-l,2,3,4-tetrahydrocarbazole l a was reacted with acetyl chloride at room tem perature for 24 h to afford a single prod­ uct 2 a in 65% yield. In its IR spectrum two bands at 3300 cm-1 and 1640 cm-1 were assigned to a NH stretching and a nitrogen carbon double bond stretching. Its !H NMR spectrum showed the pres­ ence of two singlets for two methyl protons. The methyl proton in the benzene ring, C9-C H 3, ap­ peared substantially downfield at d 2.60, the other methyl proton in the oxazole ring, C2-C H 3, ap­ peared at d 2.28. The aromatic region showed a multiplet between d 6.96-7.92, assigned of C4-H , C5-H , C6-H , C7H and C8H and a broad sin­ glet at (3 9.72 due to a NH proton, which is D 20 exchangeable. The molecular ion peak (M+) at m/ e 236 in its mass spectrum and elemental analysis: C 76.12, H 5.04 and N 11.42 are agreed to the mol­ ecular formula C 15H 12N20. Based on all these de­ tails the compound was assigned the structure 2,9dimethyloxazolo(4,5-a)carbazole (2a). Similarly oxazolo(4,5-a)carbazole derivatives 2 b e were prepared and their structures confirm­ ed by spectral and elemental analysis (Scheme 1 and Table I).