805230-79-9Relevant articles and documents
Sonogashira cross-couplings of dehydroamino acid derivatives and phenylacetylenes
Abreu, Ana S.,Ferreira, Paula M. T.,Queiroz, Maria-Joao R. P.,Gatto, Emanuela,Venanzi, Mariano
, p. 3985 - 3991 (2007/10/03)
Several phenylacetylenes were coupled under Sonogashira cross-coupling conditions with the methyl esters of N-(tert-butoxycarbonyl)-(E)-β-bromo- or -β,β-dibromodehydroalanine, to give β-substituted or β,β-disubstituted dehydroalanines, respectively. The β-substituted dehydroalanines were obtained in good to high yields (60-90%) under the usual Sonogashira conditions (1 equiv. of the phenylacetylene, 1 mol % of [Pd(PPh3)4], 2 mol % of CuI, 18 equiv. of NEt 3 in acetonitrile, 24 h at room temp.), with retention of stereochemistry. The β,β-disubstituted dehydroalanines were, in turn, obtained in moderate to good yields (44-63%) under modified Sonogashira conditions (4 equiv. of the phenylacetylene, 10 mol % of [PdCl 2(PPh3)2], 20 mol % of CuI, 1.4 equiv. of Cs2CO3 in acetonitrile, 2 h at reflux). In the latter reactions, some phenylacetylene dimer and the (E) isomer of the monosubstituted coupled products were also isolated to some extent. The Sonogashira products obtained from the 4-bromophenylacetylene were allowed to react with functionalized benzo[b]thiophenes under C-C or C-N palladium-catalyzed cross-coupling conditions. Preliminary fluorescence studies were performed for mono- and disubstituted (4-aminophenyl)acetylenic dehydroamino acids and for the benzo[b]-thiophene derivatives. The results showed that some of the dehydroalanines prepared can be used as fluorescent probes. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
