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Diastereoselective 1,3‐Dipolar Cycloadditions of Chiral Derivatives of 2‐Oxoethanenitrile Oxide to Noncyclic Conjugated Symmetrical Alkenes
Author(s) -
Romański Jan,
Jóźwik Julita,
Chapuis Christian,
Jurczak Janusz
Publication year - 2007
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200790219
Subject(s) - chemistry , nitrile , enantiomer , conformational isomerism , oxide , conjugated system , chiral auxiliary , absolute configuration , stereochemistry , medicinal chemistry , organic chemistry , enantioselective synthesis , catalysis , molecule , polymer
Asymmetric 1,3‐dipolar cycloadditions of chiral derivatives of the nitrile oxides 3a – 3c derived from (2 R )‐bornane‐10,2‐sultam, (2 R )‐10‐(dicyclohexylsulfamoyl)isoborneol, and (1 R )‐8‐phenylmenthol, to either ( E )‐stilbene 4 or dimethyl fumarate 5 , leading to the corresponding 4,5‐dihydroisoxazoles 6a – 6c and 7a – 7c in both moderate yields and diastereoselectivities, are presented. All cycloadducts were converted into the corresponding methyl esters 8 and 9 , which were used for determination of their enantiomeric purities via chiral HPLC analyses. In the case of both stilbene cycloadducts 6a and 6b , their absolute configurations were determined by X‐ray crystal‐structure analyses. These [3+2] cycloadditions suggest the participation of the thermodynamically less stable SO 2 /CO syn ‐conformer in the π y approach along the CO bond of the linear nitrile oxide 3a .