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

Reaction of SnPh 3 OH with 3‐(2‐hydroxyphenyl)sulfanylpropenoic acid [H 2 ( o ‐hpspa)] yielded [SnPh 3 (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 [SnPh 3 (BrSC)] and [SnPh 3 (Br 2 SC)], where BrSC and Br 2 SC 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 ( 1 H, 13 C and 119 Sn) 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)