A simple route to new phenanthro- and phenanthroid-fused thiazoles by a PIFA-mediated (hetero)biaryl coupling reaction

Article abstract of DOI:10.1002/1099-0690(200207)2002:13<2126::AID-EJOC2126>3.0.CO;2-A

An application of the PIFA-mediated [PIFA: phenyliodine(III) bis(trifluoroacetate) biaryl coupling reaction is presented and extended to the formation of heterobiaryl connections. A preliminary study of the scope and limitations of this procedure was carried out in the synthesis of phenanthroids 11 from a series of phenethyl-substituted heterocycles 10, It was observed that in some cases a competitive dimerization process took place. It was also found that the coupling step could be efficiently extended to a larger number of examples if an aromatic ring were situated fused to the 1,2-diarylethane skeleton, as in 23 and 30. The synthesis of a series of 4,5-diarylthiazoles 23a-g was therefore carried out to explore the electronic requirements and the regioselectivity of the PIFA-mediated non-phenolic coupling reaction. When the same procedure was applied to aryl-heteroarylthiazoles 30, a series of phenanthroid-fused thiazoles 31 was obtained in good overall yields. To the best of our knowledge, no oxidative aryl-heteroaryl coupling reaction of this type had previously been reported. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.