Preparation of 6-Hydroxy-2H-pyran-3(6H)-one from 2-Furylcarbinol by Photooxidation. Synthesis of a Pheromone of Vespa orientalis

Abstract

Photoonidation of 2-furylcarbinols followed by reduction with rriphenyl-phosphine afforded 6-hydroxy-2H-pyran-3(6H)-ones in excellent yield.The method was applied to synthesis of 6-undecylretrahydro-2-pyrone, a d her am one of Yespa orientalis.Alkylfurans, by action of pyridinium chlorochromate (PCC) in CH Cl solution, undergo an oxidative 2 2 ring fission to trans-enediones in good yields (60-9021.lLeCoff demonstrated the efficacy of furan oxidation using m-chl~roperbenzoic acid (m-CPBA) to synthesize a number of enedione-functionaliled 2 macrocycles from macrocyclic furan precursors.m-CPBA was also used to oxidize 2-furylcarbinols in CH2C12 or CHC13 for preparation of 6-hydroxy-2H-pyran-3(6H)-ones.But the yields of this reaction varied from 20% to ~5 % .~ 6-Nydroxy-2H-pyran-3(6H)-ones can be also prepared from 5-merhyl-2-4 furylcarbinols in good yields (, 85%) when it was oxidized wirh p~ridinium chlorochromare (PCC).But in our experiment, 2-furylcarbinol without methyl substitution did not give corresponding Bpyxanones as they reacted with PCC.In our result, the reacrion of 2-furylcarbinol (la) or 2-furyl-methyl carbinol (2) with PCC under the condition as Piancatellis afforded furfural or 2-aceryl- 5 f u r a n , respectively.The oxidation of 5-alkylfurylcarbinol with t-butylhydroperoxide and acidic 6 ismerization of 2,5-dimechony-2,s-dihydrofurylcarbinol can also prepare 6-hydraxy-2H-pyran-3(6H)one.1n this paper we wish to describe a useful method that is able to convert 2-furylcarbinols (1) into 6-h~droxy-2H-pyran-3(6H)-~nes (2) in excellent ~ield without electron-donating grovp attached af C-5 position, and a use of this procedure to synthesize a pheromone of orienralis.In a typical experiment the furan derivative (&) and tetraphrnylporphine (TPP) were irradiated by tungsten bromine lamp at -70'C for two hours, then excess triphenylphasphine (Ph P) dissolved in 3 CH c1 was added at the same temperature.~f t e r ten minutes the reaction mixture was taken out from 2 2 dry ice acetone bath.The products were purified by silica gel chromatography and afforded 6h y d r o ~~-2 H -~~r a n -3 ( 6 ~) -0 ~~ (&) in excellent ~ield.The result$ (12 entries) are showri in the Table I.The oxidation of -le was performed in acetone solution with methylene blue as sensitizer.