ISSN:
0941-1216
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Synthesis of 4-Alkoxy and 3-Nitro Substituted Isoxazolidines by Catalyzed 1,3-Dipolar Cycloaddition Reactionas of Nirtones with Vinyl Ethers and Nitro Alkens1,3-Dipolar cycloadditions of the C-phenyl-N-alkylnitrones 1,3 and the C,N-diphenylnitrone (2) with vinyl ethers 5,6 are strongly catalyzed by chiral oxazaborolidines derived form N-arylsulfonyl substituted L-α-amino acids valine and tert-butyl leucine and BH3·THF complex at -22 °C to room temperature to give predominantly the 3,5-trans-substituted 5-alkoxy-isoxazolidines 8b-12b, but with moderate enantioselectivity. Thermal cycloaddition afforded predominantly the 3,5-cis-substituted 5-alkoxy-isoxazolidines 8a-12a. The cycloaddition of (E)-1-ethyl-2-nitroethene (7) afforded a mixture of cis- and trans-substituted 4-nitro-isoxazolidines 13. The ratio depends on reaction temperatute and catalyst. Mild ring cleavage after quarternization of 5-etheoxy-2-methyl-isoxazolidines (8) yields the corresponding β-amino-esters 27, 28.
Additional Material:
3 Tab.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/prac.19973390175
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