Synthesis of 6H-Thieno[3,2-b]pyridin-7-ones from N-(2-X-Carbonyl)-3-thienyl Ketenimines (X = RS, ArO, R2N) via Consecutive [1,5]-X Sigmatropic Rearrangement and 6π-Electrocyclization - Alajarín, Mateo; Vidal, Ángel; Ortín, María-Mar (Synthesis, 2007)