A New Method For The Synthesis Of 3-methylthio-2, 5-diarylfuran

Furan, as one of the representive five-membered heterocycles, can be found in many naturally occurring compounds. Polysubstituted furans play an important role in organic chemistry due to their presence as key structural units in many natural products and in important Pharmaceuticals. For this reason the syntheses of polysubstituted furans continue to attract the interest of many synthetic chemist. Thio-substituted furans are particularly attractive intermediates that have found widespread usage in organic synthesis. They undergo a variety of reactions including addition/elimination, nickel-catalyzed Grignard coupling, Michael addition, ortho-metalation. Although a number of synthetic procedures are available for their formation, most of the existing methods often require harsh conditions and are frequently based on the use of a preexisting furan ring. So the development of mild method for the preparation of thio-furans from readily available starting materials is an active area of research and have broad application prospects.We have developed a new route to synthese 2-(methylthio) -2-ene-1, 4-dione from aryl methyl ketones via a self-sorting tandem reaction. It is well known that 1, 4-dione is a good precursor for the synthesis of furan via Paal-Knorr reaction and we converted the 1, 4-dione product into 3-methylthio-2, 5-diarylfuran via the modified Paal-Knorr condensation. The versatility of the MeS group was used to advantage by its ability to undergo reductive displacement to form diarylsubstituted furan, and reductive desulfuration of 3-methylthiofurans were achieved with Raney Ni in ethanol, (see Scheme 1)We have described a mild method for the preparation of 3-methylthiofurans via two steps from readily available aryl methyl ketones. Owing to the readily available starting materials, mild reaction conditions and good yields, this method should expand the scope of the formation of 3-methylthiofurans.