Synthesis of 5-Carbapterocarpens by α-Arylation of Tetralones Followed by One-Pot Demethylation/Cyclization with BBr3

5-Carbapterocarpens, one of them displaying estrogenic activity, were prepared from α-aryltetralones in high yields through a one-pot, BBr3-promoted O-demethylation and cyclization sequence. The key α-aryltetralone intermediates were obtained by direct α-arylation of tetralones with o-alkoxybromoarenes in the presence of Pd2(dba)3 (2.5 mol-%) and tBu3PHBF4 (10 mol-%) as catalysts, together with 2.5 equiv. of KOH in dioxane/H2O (4:1), under microwave irradiation conditions (80 W, 100 °C, 40 min), leading to α-monoaryltetralones in good yields.

Financial support from the Brazilian agencies Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES-DGU Project number 200/09), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) is gratefully acknowledged. The Spanish Ministerio de Ciencia e Innovación (MICINN) (project numbers PHB2008-0037-PC, CTQ2007-62771/BQU, CTQ2010-20387, Consolider INGENIO 2010 grant number CSD2007-00006), (FEDER), Generalitat Valenciana (project PROMETEO/2009/038), and the University of Alicante are also gratefully acknowledged.