Chapter 5.5 Five-membered ring systems: With N & S (Se) atoms

Abstract

The first reported regioselective lithiation of the 5-position of 3-(benzyloxy)isothiazole using LDA in diethyl ether has been described. Subsequent quench with a variety of electrophiles gave the desired products 2 in 54–68% yield. Only benzolyation proved to be unsuccessful, resulting in a complex reaction mixture. The synthesis of novel 2-cyanothiazolecarbazole analogs of ellipticine has been reported. The 3-aminocarbazole was treated with 4,5-dichloro-l,2,3-dithiazolium chloride to give the imino-l,2,3-dithiazole. Rearrangement of 38 under thermal conditions gave 39 in moderate yield. The synthesis of 2',4-disubstituted 2,4'-bithiazoles by a series of two regioselective cross coupling reactions has been reported. This bithiazole unit has been found in a number of natural products such as the bleomycins and macrocyclic antibiotics, such as cyclothiazomycin.