Mild α-Halogenation Reactions of 1,3-Dicarbonyl Compounds Catalyzed by Lewis Acids
作者:Dan Yang、Yi-Long Yan、Bob Lui
DOI:10.1021/jo026025t
日期:2002.10.1
Lewis acid Mg(ClO4)2, combined with NBS, in CH3CN or EtOAc provided mild and fast bromination of 1,3-dicarbonyl compounds. In particular, this protocol could be applied to the alpha-monobromination of alpha-unsubstituted beta-keto esters. Similar Lewis acid catalysis was also extended to the alpha-chlorination and iodination of 1,3-dicarbonyl compounds with NCS and NIS, respectively.
Highly Stereoselective Synthesis of <i>an</i><i>ti</i>-N-Protected-α-Amino Epoxides
作者:Robert V. Hoffman、Warren S. Weiner、Najib Maslouh
DOI:10.1021/jo010319h
日期:2001.8.1
A simple and efficient method for the synthesis of anti-N-protected amino epoxides from carbamate-protected amino acids is described. The two key steps are the monobromination of a beta -ketoester and chelation-controlled reduction of a bromomethyl ketone intermediate. Good overall yields, high diastereoselectivity, and excellent functional group compatibility are characteristic.
Oxidative bromination of ketones using ammonium bromide and oxone®
作者:Arun Kumar Macharla、Rohitha Chozhiyath Nappunni、Mahender Reddy Marri、Swamy Peraka、Narender Nama
DOI:10.1016/j.tetlet.2011.11.011
日期:2012.1
esters and α,α-dibromination of 1,3-diketones and β-keto esters without catalyst is reported using ammonium bromide as a bromine source and oxone® as an oxidant. The reaction proceeds at ambient temperature and yields range from moderate to excellent. Bromination of unsymmetrical ketones takes place at the less substituted α-position predominantly. Aromatisation of tetralones is also carried out with this