Novel Tandem Hydration/Cyclodehydration of α-Thiocyanatoketones to 2-Oxo-3-thiazolines. Application to Thiazolo[5,4-c]quinoline-2,4(3aH,5H)-dione Synthesis
摘要:
Novel tandem hydration of alpha-thiocyanatoketones to thiocarbamates followed by in situ cyclodehydration to fused 2-oxo-3-thiazolines is described. The reaction is applied to the synthesis of [1,3]-thiazolo[5,4-c]quinoline-2,4(3aH,5H)-diones (4). Concentrated sulfuric acid was found to be critical for the reaction as both corresponding 2,3-dioxo-1,2,3,4-tetrahydroquinolin-3-yl thiocyanates (2) and S-(2,4-dioxo-1,2,3,4-tetrahydroquinolin-3-yl) thiocarbamates (3) rapidly hydrolyze in the presence of water to 4-hydroxyquinolin-2(1H)-ones (1).
4-Hydroxy-1 H -quinolin-2-ones(1)在乙酸中与硫氰酸根反应生成相应的3-thiocyanato-1 H,3 H -quinoline-2,4-diones(2),产率高。在某些情况下,3-溴1 H,3 H-喹啉-2,4-二酮(4)被分离为次要反应产物。化合物2对亲核试剂具有很高的反应性,并容易水解为相应的4-羟基-1 H-喹啉-2-酮(1)。