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Synthesis of 1,3-Oxazine Derivatives by Palladium-Catalyzed Cycloaddition of Vinyloxetanes with Heterocumulenes. Completely Stereoselective Synthesis of Bicyclic 1,3-Oxazines
journal contribution
posted on 1999-05-07, 00:00 authored by Chitchamai Larksarp, Howard Alper1,3-Oxazines were prepared by palladium−phosphine-catalyzed cycloaddition reactions of vinyloxetanes with heterocumulenes. 4-Vinyl-1,3-oxazin-2-imines were obtained in fine yields by the
reaction of 2-vinyloxetanes with carbodiimides in THF at rt for 12 h using 1.5 mol % Pd2(dba)3·CHCl3 and 3 mol % bidentate phosphine ligands (dppe or dppp). When isocyanates were utilized in
the reaction, moderate to good yields of 4-vinyl-1,3-oxazin-2-ones were achieved within 1−2 h at
rt. Palladium-catalyzed cycloaddition of fused-bicyclic vinyloxetanes with heterocumulenes proceeds
in a highly stereoselective fashion affording only the cis-3-aza-1-oxo-9-vinyl[4.4.0]decane derivatives
in 43−98% yield.