The Regiospecific C-3 Lithiation of 5-Ethyl-2-furoic acid: An Approach to Key Natural Product Intermediates
✍ Scribed by Philip J. Perry; Vasilios H. Pavlidis; Manisha Naik
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 340 KB
- Volume
- 10
- Category
- Article
- ISSN
- 0268-2605
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✦ Synopsis
Treatment of 5ethyl-2-furoic acid with n-butyllithium in tetrahydrofuran gave regiospecific C-3 lithiation, whereas treatment of the same acid with lithium di-isopropylamide (LDA) afforded only starting material. The synthetic utility of dilithiated 5-ethyl-2-furoic acid has been demonstrated with the synthesis of two substituted 3benzyl-5-ethyl-2-furoic acid derivatives which are key intermediates for the preparation of naturally occurring cytotoxic 2ethylfuronaphthoquinones. Reaction of the C-3 lithiated species with two equivalents of benzaldehyde and subsequent reduction afforded the corresponding 3-benzyl-5-ethyl-2furoic acids. An alternative route to 5ethyl-2-furoic acid has been described allowing for a more convenient preparation of longer-chain 5-alkyl-2furoic acids.