Journal article
The asymmetric synthesis of 2-benzopyrans and their quinones through intramolecular diastereoselective ring-closure of titanium phenolates of phenolic aldehydes
Journal of the Chemical Society, Perkin Transactions 1, (20), pp.3039-3048
1999
Abstract
Treatment of the phenolic aldehyde (α′S,2S )-2-(5′-hydroxy-2′-methoxy-α′-methylbenzyloxy)propanal 15 with titanium tetraisopropoxide followed by ultrasonication led to its completely diastereoselective cyclisation in high yield to afford (1S,3S,4R)-3,4-dihydro-1,3-dimethyl-8-methoxy-2-benzopyran-4,5-diol 18, which was characterised as its more stable 4,5-diacetate 19. The diastereomeric (α′R,2S )-2-(5′-hydroxy-2′-methoxy-α′-methylbenzyloxy)propanal 17 on similar treatment gave rise to a mixture of (1R, 3S, 4R)- and (1R, 3S, 4S )-3,4-dihydro-1,3-dimethyl-8-methoxy-2-benzopyran-4,5-diols 21 and 23, isolated as the 4,5-diacetates 22 and 24, in a ratio of 3∶1. Oxidative dealkylation of the diol 18 with silver(II) oxide afforded (1S,3S,4R)-3,4-dihydro-1,3-dimethyl-4-hydroxy-2-benzopyran-5,8-quinone 2 in high yield, while the epimeric 1R quinone 40 was similarly obtained from diol 21.
Details
- Title
- The asymmetric synthesis of 2-benzopyrans and their quinones through intramolecular diastereoselective ring-closure of titanium phenolates of phenolic aldehydes
- Authors/Creators
- R.G.F. Giles (Author/Creator)C.A. Joll (Author/Creator)
- Publication Details
- Journal of the Chemical Society, Perkin Transactions 1, (20), pp.3039-3048
- Publisher
- Royal Society of Chemistry
- Identifiers
- 991005540522807891
- Copyright
- © 1999 Royal Society of Chemistry
- Murdoch Affiliation
- School of Chemical and Mathematical Science
- Language
- English
- Resource Type
- Journal article
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