Stereochemical studies 136. saturated heterocycles 141.1 synthesis and conformational study of stereoisomeric 2,2-disubstituted-5,6-tri- and -5,6-tetramethylene-tetrahydro-1,3-oxazin-4-ones (original) (raw)

Diastereomers of 2,2-disubstituted-5,6-tri-and 5,6-tetramethylenetetrahydro-1,3-oxazin-4-ones (5a,b-12a,b) were synthesized from cis-2-hydroxycyclopentane and-cyclohexanecarboxamides (3, 4) bv condenza them with 2-butanone, 3-methyl-2-butanone, 3,3-dimethyl-2-butanone or acetophenone. The stereoselectivity of the ring closure depends on the steric requirements of the C-2 geminal substituents, although the predominant conformation (O-in) remains the same in both sets of the heterocycles. _-Although the synthesis of 2,3-dihydro-1,3-benzoxazin-4-ones has been known since the beginning of this century, and their pharmacology2 has also been thoroughly studied, the synthesis,2-5 stereochemistry5-7 and pharmacology*