SCHEDULED MAINTENANCE
The stereoselectivity of addition of N-benzyl-C-alkylnitrones to methyl crotonate. X-Ray crystal structure of (3RS,4SR,5RS)-2-benzyl-4-methoxy-carbonyl-5-methyl-3-[(4RS)-2,2,5,5-tetramethyl-1,3-dioxolan-4-yl]isoxazolidine
Abstract
The addition of N-benzyl-C-alkyl- and N-benzyl-C-β-alkoxyalkyl-nitrones (1a–d) to methyl crotonate gave predominantly the 3,5-trans-substituted isoxazolidines (2a–d), selectivity ca. 3 : 1, whereas N-benzyl-C-α-alkoxyalkylnitrones (1e, f) gave more of the 3,5-cis-substituted isoxazolidines (3e, f) with selectivities of ca. 1 : 4.
The chiral dimethyldioxolanyl nitrone (4) showed only modest diastereoface selectivity in its addition to methyl crotonate. However the more hindered tetramethyldioxolanyl nitrone (13) was more stereoselective, providing adduct (14) as the only significant product. The structure of this adduct was established by X-ray diffraction.
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