546110-09-2Relevant academic research and scientific papers
Synthesis of thiochromen-4-one-annelated heterocycles: Regioselective cyclization of 3-hydroxy-2-cyclohex-2′-enylthiochromen-4-one
Majumdar,Roy
, p. 133 - 142 (2003)
2-Cyclohex-2′-enyl-3-hydroxythiochromen-4-one (4) was synthesized in 80% yield by the thermal [3,3] sigmatropic rearrangement of 3-cyclohex-2′-enyloxythiochromen-4-one (3). Treatment of 4 with palladium (bisbenzonitrile) chloride in refluxing benzene afforded linearly cyclized product, tetrahydrobenzofuro[3,2-b]thiochromen-6-one (5) in 98% yield which on dehydrogenation with palladized charcoal gave benzofuro[3,2-b]thiochromen-6-one (6). Substrate 4 on reaction with hexamethylenetetramine hydrotribromide gave a mixture of three products, linearly cyclized heterocycle 10 (35%), bicyclic heterocyclic 8 (15%), and dibromide 9 (20%). The same reaction when conducted with pyridine hydrotribromide furnished only the dibromide 9 which was then cyclized in acetone-potassium carbonate to give the bicyclic compound 8 in 85% yield. The dibromide 9 was cyclized by heating with palladized charcoal in diphenyl ether to give a mixture of linearly cyclized product 5 (7%) and bicyclic product 8 (63%). Substrate 4 was also cyclized in cold conc. H2SO4 to give a bicyclic product 11 in 95% yield.
