S. A. Vakarov, D. Gruzdev, L. S. Sadretdinova
Mar 28, 2015
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Journal
Tetrahedron-asymmetry
Abstract
Abstract In the search for novel efficient chiral resolving agents, we have studied the diastereoselective acylation of 3,4-dihydro-3-methyl-2 H -[1,4]benzoxazine and 7,8-difluoro-3,4-dihydro-3-methyl-2 H -[1,4]benzoxazine with acyl chlorides of 2-phenoxy carboxylic acids (2-phenoxypropionic, 2-phenoxyisovaleric, and 2-phenoxy-3-phenylpropionic) in toluene and dichloromethane at different temperatures. HPLC analysis of the acylation products showed the predominant formation of ( R ∗ , S ∗ )-diastereoisomeric amides in all cases. It was found that acylation with the studied acyl chlorides was highly stereoselective; 2-phenoxyisovaleryl chloride demonstrated the highest stereoselectivity (selectivity factor s up to 499). A model for the diastereoisomeric transition states in the interaction between racemic amine and acyl chloride is proposed.