176911-54-9Relevant academic research and scientific papers
Intramolecular Diels-Alder additions to 2-benzopyran-3-ones; anti-selectivity induced by the phenylsulfonyl group
Bush, Edward J.,Jones, David W.,Ryder, Tracie C. L. M.
, p. 1929 - 1938 (2007/10/03)
Intramolecular Diels-Alder additions of the 2-benzopyran-3-ones 2d, 2e and 2f with an E-SO2Ph substituent on the dienophile (X = SO2Ph in 2) show greatly enhanced exo-addition of the tether than is shown in the absence of the E-SO2Ph group (X = H in 2). For 2e and 2f, exo-chain addition becomes preferred, and for 2d, endo-chain addition much less preferred, than in related cases with X = H. An E-CO2Me group on the dienophile is also effective in enhancing exo-chain addition, but less effective than an E-SO2Ph group. The adducts 4e and 4f undergo reductive elimination (5% Na-Hg) to give the diterpene related products 32 and 33 respectively.
Intramolecular Diels-Alder additions to 2-benzopyran-3-ones; endo-selective additions and some reactions of the adducts
Jones, David W.,Nongrum, Firstborn Matthew
, p. 705 - 713 (2007/10/03)
Unlike o-quinodimethanes lacking a bridge between the termini of the diene system e.g. 18a (n = 3 or 4), the 2-benzopyran-3-ones 10a, 10b and 10c undergo endo-selective intramolecular Diels-Alder addition of the connecting chain to give cis-BC fused ring systems of type 13. The adduct 13b is converted into the ester 21 with methanolic HCl and into the ketol 36 by LiAlH4 reduction followed by oxidation (MnO2). The ketone 31 is prepared from 21 by epoxidation followed by BF3·Et2O-catalysed rearrangement; with NaOMe-CD3OD it fails to undergo cis-trans isomerisation and fails to incorporate deuterium at C-8 probably due to the overwhelming acidity of the C-6 protons. The cis-dihydronaphthalene 26 obtained from 21 gives cis-21 with KOBut-(CD3)2SO showing the greater thermodynamic stability of the cis-fused ring system in this case.
