176911-47-0Relevant academic research and scientific papers
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.
