1 Sonogashira cross-couplings of dehydroamino acid derivatives and phenylacetylenes Ana S. Abreu, a Paula M. T. Ferreira, a Maria-João R. P. Queiroz, a * Emanuela Gatto, b Mariano Venanzi b a Departamento de Química-Universidade do Minho, Gualtar 4710-057 Braga (Portugal) b Department of Chemical Sciences and Technologies, University of Tor Vergata 00133 Rome (Italy) *Corresponding author: Fax: +351253678983 E-mail: mjrpq@quimica.uminho.pt Received Keywords: Amino acids / phenylacetylenes / Sonogashira coupling / palladium / benzo[b]thiophenes/ fluorescence _____________________________________________________________________________ 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 respectively β-substituted or β, β-bis-substituted dehydroalanines. 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% Pd(PPh 3 ) 4 , 2 mol% CuI 18 equiv. NEt 3 in acetonitrile, 24h at rt) with maintenance of the stereochemistry. The β, β-bis-substituted dehydroalanines were in turn obtained in moderate to good yields (44-63%) requiring modified Sonogashira conditions (4 equiv. of the phenylacetylene,10 mol% PdCl 2 (PPh 3 ) 2 , 20 mol% CuI, 1.4 equiv. Cs 2 CO 3 , 2h at reflux of acetonitrile). In the latter reactions some phenylacetylene dimer and the (E)-isomer of the mono substituted coupled products were also isolated in some extent. The Sonogashira products which were obtained from the 4-bromophenylacetylene were reacted with functionalized benzo[b]thiophenes under C-C or C-N palladium-catalyzed cross-coupling conditions.