Formation of 3‐Sulfanylcoumarins by SnPh3OH‐Promoted Cyclization of 3‐Aryl‐2‐Sulfanylpropenoic Acids

Reaction of SnPh3OH with 3-(2-hydroxyphenyl)sulfanylpropenoic acid [H2(o-hpspa)] yielded [SnPh3(SC)], where SC is deprotonated 3-sulfanylcoumarin (3-sulfanyl-2H-1-benzopyran-2-one, HSC), by a cyclization process. Similarly, when 3-(2-hydroxy-5-bromophenyl)- and 3-(2-hydroxy-3,5-dibromophenyl)-2-sulfanylpropenoic acids were treated with the same tin hydroxide, the cyclization resulted in [SnPh3(BrSC)] and [SnPh3(Br2SC)], where BrSC and Br2SC are the new ligands formed from the deprotonation of 3-sulfanyl-6-bromocoumarin and 3-sulfanyl-6,8-dibromocoumarin, respectively. The new compounds were characterized by elemental analysis, multinuclear NMR (1H, 13C and 119Sn) and vibrational spectroscopy, and mass spectrometry. Single-crystal X-ray structures of these complexes all showed that the tin atom is surrounded by three phenyl C atoms and the S and O atoms of the bidentate ligand in a distorted trigonal-bipyramidal environment. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)