The Synthesis and Chemistry of Functionalized Furochromones. 2. The Synthesis, Sommelet-Hauser Rearrangement, and Conversion of 4,9-Dimethoxy-7--5H-furobenzopyran-5-one to Ammiol

Article abstract of DOI:10.1021/jo00200a002

Condensation (NaH/THF) of khellinone 14 with ethyl 2-(methylthio)acetate followed by acid-catalyzed cyclodehydration in methanolic HCl yielded 4,9-dimethoxy-7-<(methylthio)methyl>-5H-furo<3,2-g><1>benzopyran-5-one (10).Condensation of 14 with ethyl 2-(phenylthio)acetate followed by cyclodehydration yielded the corresponding C-7 (phenylthio)methylene analogue 11.Sulfide 10 was converted to sulfonium salt 17 which upon treatment with base yielded the rearranged sulfide 18, 4,9-dimethoxy-6-<(methylthio)methyl>-7-methyl-5H-furo<3,2-g><1>benzopyran-5-one.Desulfurization of 18 yielded the 6,7-dimethylfurochromone 19 while treatment of both 18 and 10 with N,N-dimethylformamide dimethyl acetal yielded 20 and 21, respectively.Periodate oxidation of 10 yielded sulfoxide 24 which underwent Pummerer rearrangement to give acetoxy sulfide 25.Hydrolysis of 25 (to give 2) and Meerwein-Ponndorf-Verley reduction then yielded ammiol 4.Treatment of 10 with excess methyl iodide yielded the known allylic iodide 5. treatment of 5 with KO2 or KOAc and then basic hydrolysis of that acetate likewise yielded ammiol.Treatment of 5 with N,N-dimethylamine afforded the C-7 aminomethylene analogue 27 in 96percent yield.