%0 Journal Article
%T Polymer-Assisted Synthesis of Single and Fused Diketomorpholines
%J -
%D 2019
%R https://doi.org/10.1021/acscombsci.8b00176
%X The synthesis of different diketomorpholines via N-acyl-3,4-dihydro-2H-1,4-oxazine-3-carboxylic acids is reported in this article. The key intermediates were prepared using a convenient solid-phase synthesis starting from polymer-supported Ser(tBu)-OH. After subsequent sulfonylation with 4-nitrobenzenesulfonyl chloride (4-Nos-Cl), alkylation with an ¦Á-bromoketone, cleavage of the 4-Nos group and acylation with an ¦Á-halocarboxylic acids, acid-mediated cleavage from the resin yielded dihydrooxazine-3-carboxylic acids in high crude purities. Depending on the reaction conditions, exposure to base resulted in cyclization to either oxazino[3,4-c][1,4]oxazine-diones or 3-methylidenemorpholine-2,5-diones. Further reaction with triethylsilane-trifluoroacetic acid (TES/TFA) led to olefin reduction, in the case of oxazino[3,4-c][1,4]oxazine-dione with full control of the newly formed stereocenter
%U https://pubs.acs.org/doi/10.1021/acscombsci.8b00176