3 -Furanone dienolate

As shown in Scheme 36,2,2-disubstituted-5-alkyl-3(2//)-furanones also undergo -y-alkylation via their extended dienolate intermediates (75). Similarly, 4-isopropyl-6-methyl-(2H)-pyran-2-one, which may be regarded as a vinylogous S-alkyl-3(2//)-furanone, was deprotonated and alkylated at the methyl group. ... 

Furanone (16) gives a dienolate that shows a proclivity for reaction with electrophiles at the exocyclic 7-position (equation 30). Dehydration of the mixture of diastereomeric aldols gives a 1 1 mixture of geiparvarin (17) and its geometric isomer. 

The spiro-dihydrofuran (61) is converted into the cyclobutane derivative (62) under the influence of trifluoroacetic acid. The lithium dienolate (64), derived from the furanone (63), yields solely y-alkylated products on treatment with alkyl halides. Thermolysis of the t-butylperoxybutenolide (65) produces about equal amounts of the hydroxy-furanone (67) and the indenone (68), presumably via the oxide radical (66). Attack of iodide ion on the salt (69) results in the formation of methyl iodide, butanolide, and (surprisingly) methyl 4-iodobutanoate. A description of a study of the photochemical rearrangement of the tetrahydrofurans (70) to the bicyclic oxetans (71) has been presented. ... 

Palladium-catalyzed asymmetric allylic alkylation of allyl dienol carbonates afforded the furanones in both high yields and high enantioselectivities. This reaction was used as the key step in the total synthesis of (-)-roccel-laric acid and (-)-nephrosteranic acid (13AGE1257). 

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