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Generation of and diastereoselective cycloaddition reactions to ortho-quinodimethane tricarbonylchromium intermediates
|Published in||Tetrahedron. 1993, vol. 49, no. 25, p. 5599 - 5615|
|Abstract||Reaction of n-BuLi with either syn- or anti-(1-acetoxycyclobutabenzene)Cr(CO)3 or with syn-(1-hydroxycyclobutabenzene) generates a planar chiral o-quinodimethane complex intermediate at temperatures below 0 °C. This reacts with reactive dienophiles (methyl acrylate, acrylonitrile, phenyl vinyl sulfone, 1-phenyl-2-(phenylsulfonyl)ethene, methyl crotonate, dimethyl fumarate and dimethyl maleate) to give cycloaddition products. X-ray structures of three complexes show that (anti-1-tetrahydronaphthol)Cr(CO)3 complexes are formed selectively. With ester and nitrile substituted olefins, the major diastereoisomer is the cis product (endo-addition) whereas the trans product (exo addition) is largely preferred for vinyl sulfones. The results are compared with those obtained with the free cyclobutabenzenes. After decomplexation, the ß-hydroxy ester products can be alkyl- or allylated highly diastereoselectively. First examples of diastereoselective complexation of enantiomerically enriched cyclobutabenzenes are reported.|
|KUNDIG, Ernst Peter, LERESCHE, James. Generation of and diastereoselective cycloaddition reactions to ortho-quinodimethane tricarbonylchromium intermediates. In: Tetrahedron, 1993, vol. 49, n° 25, p. 5599 - 5615. https://archive-ouverte.unige.ch/unige:6609|