4ff-Pyran-4-one

Additional compounds found in the pheromone gland of female cigarette beetles are (2S,3R,l R)-2,3-dihyro-2-ethyl-3,5-dimethyl-6-(r-methyl-2 -oxo-butyl)-4ff-pyran-4-one 121 (P-serricorone), its (rs)-epimer (a-serricorone), and its reduction product, serricorole, 122 which shows (l/S,2/S)-configuration [245-247]. These compounds showed only weak attractivity [245], however, they obviously act as oviposition deterrents [248,249]. 

The pheromone produced by females of the drugstore beetle was the first to be identified in an anobiid beetle 2,3-dihydro-2,3,5-trimethyl-6-(r-methyl-2 -oxobutyl)-4ff-pyran-4-one (stegobinone) [256] which by independent synthesis [257] was shown to keep (2S,3R,1 R)-configuration 123. A second compound... 

The assumption is made that the combining ratio for the alcoholate is identical to that for the hydroxide adduct. Percentages are in mole percent. Solvent remaining after vacuum treatment at 25° foi 16 hr. 3-Hydroxy-2-methyl-4ff-pyran-4-one. d Use of methanol instead of ethanol gave a 1.8 1 complex that consisted of 70% of alcoholate and 30% of adduct. 

H NMR data have been reported for 2,6-dimethyl- and 2,6-diphenyl-4ff-pyran-4-one and -thiopyran-4-one and -selenopyran-4-one, in their neutral and protonated forms (75MI2). 

Similarly prepared were 3-acetoxy-2,3-dihydro-4ff-pyran-4-one (2 Rj = H, Rj = OAc) [from l-methoxy-2-acetoxy-3-trimethylsilyloxy-l,3-butadiene (1 Rj = H, R2 = OAc) and paraformaldehyde in 67% yield] and 5-acetoxy-3-benzoyloxy-2,3-dihydro-4H-pyran-4-one (from l-benzoyloxy-2-t-butyldimethylsilyloxy-3-acetoxy-4-methoxy-l,3-butadiene and paraformaldehyde in 75% yield). 

OjCjHj, Methyl benzoate, chromium complex, 26 32, 28 139 OjCgHij, 4ff-Pyran-4-one, 2,3,5,6-tetra-hydrido-2,3,5,6-tetramethyl-, 29 193 02C,oHg, 2,3-Naphthalenediol, in prepn. of cu-tetraamminedihaloruthenium(III) complexes, 26 66, 67... 

Stegobinone [(25,3R, 1 R)-2,3-dihydto-2,3,5-tii-methyl-6-( 1 -methyl-2-oxobutyl)-4ff-pyran-4-one]. 

A synthetic procedure to insert the perfluoroalkyl group into the dihydropyrone cycle via ethoxybutenone has been elaborated (98T2819). 6-Ethoxy-2-trifluoro-methyl-4ff-pyran-4-one (309) was synthesized by the condensation of ethyl... 

Indole-fused pyran-4-ones are prepared in one-pot two-step synthesis. In the first there is the acylation of 1-substituted 3-acetyl-lH-indol-2-ols with acid chlorides using triethylamine as base, in dichloromethane at room temperature. The second consists in the 4ff-pyran-4-one ring formation firom the in situ-obtained 3-acetyl-2-acyloxy-lF/-indole derivatives (13S1235).A highly diastereo- and enantioselective organocatalytic formal hDA reaction of enones with isatins occurs in the presence of amine 34, acid 35, and thiourea 36 to produce spirooxindole tetrahydro-4ff-pyran-4-ones (Scheme 59) (13CEJ6213). 

Methoxytetrahydropyranyl derivatives (31) may be readily prepared by the acid-catalyzed addition of 4-methoxy-5,6-dihydro-2i/-pyran (32) [64] to alcohols. In the case of nucleosides, good yields of pure crystalline monoketals [such as 2 -0-methoxytetrahydropyranyluridine (33)] and bisketals [such as 34 (B = pyrimidine or purine base)] have been obtained [64]. The methoxytetrahydropyranyl group has satisfactory hydrolysis properties in that (33) is approximately three times as labile to aqueous acid as the corresponding tetrahydro-pyranyl derivative (19) [52b]. Since a simple procedure has recently been developed [66] for the preparation of tetrahydro-4ff-pyran-4-one, the enol ether (32) has become a readily accessible reagent. 

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