1380449-77-3Relevant academic research and scientific papers
Ring size and substituent steric effects in cyclic ketene-N,O/S-acetal trifluoroacetylations
De Silva, Hondamuni I.,Song, Yingquan,Henry, William P.,Pittman Jr., Charles U.
, p. 2965 - 2970 (2012)
Trifluoroacetylations of cyclic ketene-N,O/S-acetals exhibit a ring size effect. The five-membered rings 2,4,4-trimethyl-2-oxazoline, 2-methyl-2-oxazoline, and 2-methyl-2-thiazoline, each form cyclic ketene-N,O/S-acetal intermediates which then react with trifluoroacetic anhydride to give β-monotrifluoroacetylation products. Conversely, the six-membered ring 2-methyl-2-oxazine gives its β,β- bistrifluoroacetylation product. In situ-generated five-membered ring N-Me cyclic ketene-N,O-acetals, 3,4,4-trimethyl-2-methylene-oxazolidine, and 3-methyl-2-methylene-oxazolidine, and six-membered ring 3-methyl-2-methylene-1, 3-oxazinane were each β,β-bistrifluoroacetylated. However, 3-methyl-2-methylene-oxazolidine also afforded a γ-lactam by an iodide-catalyzed rearrangement of its β,β-bistrifluoroacetylated derivative. In situ-generated 3-methyl-2-methylene-thiazolidine gives both β-mono- and β,β-bistrifluoroacetylation products and no lactam, in contrast to its N,O-analog 3-methyl-2-methyleneoxazolidine.
