A Novel Method for the Synthesis of 4h-Pyran-4-One Derivatives

Improved method for preparation of dibenzocrown-containing 4H-pyran- 4-one and synthesis of merocyanine dyestuffs from it

“…Later a more successful synthetic pathway to pyrone 2 was found starting from chelidonic acid [8]. At approximately the same time another approach to the synthesis of compound 2 was proposed, from di(methoxycarbonyl)pyran-4-one 3 [11].…”

“…We have developed a preparative method for the synthesis of compound 2, the yields of intermediate products were greater and the methods more convenient than claimed in [11]. Bromination of pyrone 3 was conducted best in diethyl ether (on carrying out the reaction in methylene chloride [11] a mixture of mono-and polybromo derivatives was formed).…”

“…Bromination of pyrone 3 was conducted best in diethyl ether (on carrying out the reaction in methylene chloride [11] a mixture of mono-and polybromo derivatives was formed). On adding bromine to an ether solution of compound 3 a reddish solid was formed, which is probably a complex of bromine with the starting material, the solution itself remained colorless.…”

“…Under these conditions 2,6-bis(bromomethyl)pyran-4-one (2) is formed in good yield. The use of 50% H 2 SO 4 also leads to product 2, but in lower yield, and adding acetic acid, as proposed in [11], is undoubtedly a negative factor.…”

A convenient method for the synthesis of hydroxymethyl and carboxaldehyde derivatives of 3,5-diphenyl-4H-pyran-4-one

“…Many new methods for their synthesis have been reported [7][8][9][10] . Some 4H-pyran-4-ones containing a carboxaldehyde group may be prepared by oxidation of a hydroxymethyl group in derivatives of kojic acid [11][12][13] , formylation of pyrones in the presence of trifluoroacetic acid 14 , and condensation of a methyl group at positions 2 and 6 of 4H-pyran-4-one derivatives with an aldehyde, followed by oxidation of the resultant styryl group by OsO 4 and KIO 4 9 (Scheme 1).…”