Richard Kammel, Denisa Tarabová, Z. Růžičková
May 13, 2015
Citations
0
Influential Citations
11
Citations
Journal
Tetrahedron Letters
Abstract
Abstract The reactions of 3-bromo-1-benzofuran-2(3 H )-one ( 1a ) and 3-bromo-1,3-dihydro-2 H -indol-2-one ( 1b ) with 4-methoxythiobenzamide and thiourea under mildly basic conditions are reported. While brominated lactone 1a gave the expected 5-(2-hydroxyphenyl)-2-(4-methoxyphenyl)-1,3-thiazol-4-ol ( 2 ) or 2-amino-5-(2-hydroxyphenyl)-1,3-thiazol-4(5 H )-one ( 5 ) products, the analogous brominated lactam 1b reacted with the thioamide via an unexpected Eschenmoser coupling reaction to give (3 Z )-3-[amino(4-methoxyphenyl)-methylidene]-1,3-dihydro-2 H -indol-2-one ( 3 ). When lactam 1b was treated with thiourea, isoindigo ( 4 ) was the only isolated product. The reaction mechanisms, involving formation of α-thioiminium or isothiouronium salts and their base-catalyzed decomposition are also proposed.