Keto ethers. IV. Products formed on reaction of dihydro-2,2,5,5-tetramethyl-3(2H)-furanone with strong acids

Abstract

Can. J. Chem. 65, 1695Chem. 65, (1987. Reaction of tetrahydro-2,2,5,5-tetramethyl-3(2H)-furanone (1) with 96 or ca. 100% sulfuric acid or hot polyphosphoric acid followed by aqueous quenching gave the following products: 2-hydroxy-2,5-dimethyl-4-hexen-3-one (3), 2,4,4-trimethyl-2-cyclopenten-1-one (7), 3,5,5-trimethyl-2-cyclopenten-1-one (8), tetrahydro-3,4,5,5-tetramethylfuran-2,3-diol ( l l ) , 2,5-dihydro-3,5,5-trimethyl-2-methylenefuran (17) and its dimer 20, 2,5-dihydro-2,3,5,5-tetramethyl-2-furanol (IS), 4-hydroxy-2,4-dimethyl-2-pentenoic acid y-lactone (22), 2,3,5-trimethyl-2-cyclopenten-1-one (23), and tetramethylfuran (25). In 96% sulfuric acid the products arise by ring opening, ring opening followed by reclosure to carbocyclic products, methyl migration from C-2 to C-3 to give rearranged furan derivatives, and oxidation. Inca. 100% sulfuric acid or hot polyphosphoric acid further methyl migrations can occur to give 23 and 25.PETER YATES et PATRICK MICHAEL BURKE. Can. J. Chem. 65, 1695Chem. 65, (1987.La reaction de la tetrahydro tCtramCthyl-2,2,5,5 2H-furannone-3 (1) avec de I'acide sufurique a 96 ou t i environ 100% ou avec de l'acide polyphosphorique chaud, suivie par un piCgeage avec de l'eau, conduit aux produits suivants : l'hydroxy-2 dimethyl-2,5 hexkne-4 one-3 (3), la trimithyl-2,4,4 cyclopentkne-2 one-1 (7), la trimethyl-3,5,5 cyclopentkne-2 one-1 (8), le tetrahydro tCtramCthy1-3,4,5,5 furannediol-2,3 (11), le dihydro-2,5 trimethyl-3,5,5 mCthyl6ne-2 furanne (17) There have been many investigations of the reactions of organic compounds with strong acids (3, 4). Several of these have concerned substrates with saturated or unsaturated carbony1 functions. Less attention has been paid to carbonyl compounds containing other functional groups. We report on an investigation of the variety of reactions undergone by the keto ether 1 in strongly acidic media.3 We describe here the isolation and determination of the structures of the products formed in such reactions and plan, in a subsequent publication, to discuss the formation of these products in terms of the site(s) of protonation of 1 and the nature of the cationic intermediates.Compound 1 is readily available from the ynediol 2 (6). Reactions in strongly acidic media followed by aqueous quenching gave mixtures of products whose composition was dependent on both the nature of the medium and the time of reaction. These products were isolated by standard procedures and identified by their spectra (Tables 1 and 2) and by comparison in most cases with independently synthesized samples.Vapor phase chromatographic (vpc) analyses of product mixtures from 96% sulfuric acid showed that one compound was formed rapidly and that the amount of this product reached a maximum after 2 h and then fell to zero after several days. This compound was shown to be 3 by comparison with an authentic

Carbonylation of Alkynyl Epoxides: Synthesis of 5-Hydroxy-2,3-dienoate Esters and 2,3-Dihydrofuran-3-ol Derivatives

“…Deprotection of 9. A 250 mg amount of 9 (0.78 mmol) was dissolved in 5 mL of THF and treated at 0 °C with tetra- n -butylammonium fluoride (2 equiv) for 5 min. The mixture was stirred at room temperature for 40 min.…”

Anionic cascade reactions. One-pot assembly of (Z)-chloro-exo-methylenetetrahydrofurans from β-hydroxyketones

“…1. Increasing the steric hindrance at the tertiary alcohol site resulted in the exclusive formation of the syn -dioxanes 37 and 38 respectively, albeit at the expense of the yield [32–38]. …”

Total Syntheses of Marrubiin and Related Labdane Diterpene Lactones

“…With tricyclic compound 26 in hand, efforts were next focused on the transformation of the cyclopentenone moiety to the corresponding γ-butyrolactone. With regard to the oxidative cleavage of the cyclopentenone ring, it was found that desired γ-ketocarboxylic acid 27 could be obtained upon exposure of enone 26 to ozone in CH 2 Cl 2 at −78 • C followed by either reductive (Me 2 S) or oxidative (H 2 O 2 , NaOH) workup [32], but the reaction suffered from low yield (33%) and reproducibility issues. While α-ketocarboxylic acid 28, detected as a byproduct, could be converged to γ-ketocarboxylic acid 27 upon treatment with H 2 O 2 in aqueous NaOH/THF, no improvement in overall yield was observed.…”