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A two-phase bromination process using tetraalkylammonium hydroxide for the practical synthesis of α-bromolactones from lactones
- Source :
- Beilstein Journal of Organic Chemistry, Vol 17, Iss 1, Pp 2906-2914 (2021)
- Publication Year :
- 2021
- Publisher :
- Beilstein-Institut, 2021.
-
Abstract
- A simple and efficient method for α-brominating lactones that affords α-bromolactones under mild conditions using tetraalkylammonium hydroxide (R4N+OH−) as a base was developed. Lactones are ring-opened with Br2 and a substoichiometric amount of PBr3, leading to good yields of the corresponding α-bromocarboxylic acids. Subsequent intramolecular cyclization over 1 h using a two-phase system (H2O/CHCl3) containing R4N+OH− afforded α-bromo lactones in good yields. This method can be applied at the 10 mmol scale using simple operations. α-Bromo-δ-valerolactone, which is extremely reactive and difficult to isolate, could be isolated and stored in a freezer for about one week using the developed method. Optimizing the solvent for environmentally friendly large-scale syntheses revealed that methyl ethyl ketone (MEK) was as effective. In addition, in situ-generated α-bromo-δ-valerolactone was directly converted into a sulfur-substituted functional lactone without difficulty by reacting it with a sulfur nucleophile in one pot without isolation. This new bromination system is expected to facilitate the industrial use of α-bromolactones as important intermediates.
Details
- Language :
- English
- ISSN :
- 18605397
- Volume :
- 17
- Issue :
- 1
- Database :
- Directory of Open Access Journals
- Journal :
- Beilstein Journal of Organic Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.4bdccb111f0545ad8ad5ea5f20007c41
- Document Type :
- article
- Full Text :
- https://doi.org/10.3762/bjoc.17.198