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Issue 0, 1974
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Allyl and prop-2-ynyl ethers in the phloroglucinol series and their thermal rearrangements. An alternative synthesis of deoxyhumulone and its analogues

Abstract

Treatment of phloroacetophenone (2′,4′,6′-trihydroxyacetophenone) with prop-2-ynyl bromide and potassium carbonate gave 2′-hydroxy-4′,6′-bis(prop-2-ynyloxy)acetophenone (3; R = H), 2′,4′-dihydroxy-6′-(prop-2-ynyloxy)acetophenone (4; R1= CH2C⋮CH, R2= H), 8-acetyl-2,3,5,6-tetrahydro-2,5-dimethylenebenzo-[1,2-b:3,4-b′]difuran-7-ol (5), and other minor products including 6′-hydroxy-5′-(prop-2-ynyl)-2′,4′-bis(prop-2-ynyloxy)acetophenone (9).

Hydrogenation of (3; R = H) with quinoline–sulphur-poisoned palladium was only partially selective giving 2′,4′-bis(allyloxy)-6′-hydroxyacetophenone (2; R1= Me, R2= H) as the predominant product. Thermal rearrangement of (2; R1= Me, R2= H) in refluxing N-methylpiperazine under nitrogen gave 3′-allyl-4′-allyloxy-2′,6′-dihydroxyacetophenone (12) in 55% yield whilst rearrangement in refluxing NN-diethylaniline gave the deoxyhumulone analogue, 3′,5′-diallyl-2′,4′,6′-trihydroxyacetophenone (1; R1= Me, R2= H) in 85% yield.

Attempted etherification of phloroacetophenone with 1,1-dimethylprop-2-ynyl chloride in dry acetone gave no reaction but in the presence of water the major product was 8-acetyl-2,2-dimethylchromen-5,7-diol (13; R = H). Amongst other products were 7-acetyl-2,3-dihydro-3,3-dimethyl-2-methylenebenzo[b]furan-4,6-diol (14; R = H), which was transformed by dilute acid to 7-acetyl-2,3-dihydro-2,3,3-trimethylbenzo[b]furan-2,4,6-triol (18), 6-acetyl-2,2,8,8-tetramethyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-5-ol (7), and 8-acetyl-5-(1,1-dimethylprop-2-ynyloxy)-2,2-dimethylchromen-7-ol (20). Similar attempts to etherify 3′,5′-diacetylphloroacetophenone gave 6,8-diacetyl-2,2-dimethylchromen-5,7-diol (13; R = Ac) and 5,7-diacetyl-2,3-dihydro-3,3-dimethyl-2-methylenebenzo[b]furan-4,6-diol (14; R = Ac).

Thermal rearrangement of 2-isovaleryl-4,4-bis-(3-methylbut-2-enyl)cyclohexane-1,3,5-trione (26; R = Me2CHCH2) gave a complex mixture including 2,4,6-trihydroxy-3,5-bis-(3-methylbut-2-enyl)isovalerophenone (deoxyhumulone)(1; R1= Me2CHCH2, R2= Me)(10%) and 8-isovaleryl-2,2-dimethyl-6-(3-methylbut-2-enyl)chroman-5,7-diol (30).

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Article information


J. Chem. Soc., Perkin Trans. 1, 1974, 944-952
Article type
Paper

Allyl and prop-2-ynyl ethers in the phloroglucinol series and their thermal rearrangements. An alternative synthesis of deoxyhumulone and its analogues

E. Collins and P. V. R. Shannon, J. Chem. Soc., Perkin Trans. 1, 1974, 944
DOI: 10.1039/P19740000944

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