Breslow, Ronald published the artcileSubstrate selectivity in epoxidation by metalloporphyrin and metallosalen catalysts carrying binding groups, Recommanded Product: 3-Methylbut-2-en-1-yl benzoate, the publication is Journal of the American Chemical Society (1989), 111(12), 4517-18, database is CAplus.
Iron porphyrin I has been synthesized. With 4 equiv of Cu2+ I catalyzes the epoxidation of cis-2-butene-1,4-diol dinicotinate (II) with a 40-fold increase in reactivity compared with a non-complexing substrate, as determined in direct competition experiments This reaction was essentially stereospecific in forming the cis epoxide, whereas without the added Cu2+ ca. 8% of the product epoxide was trans. By contrast, the mononicotinate monobenzoate (III) of the diol shows only a 2-fold selectivity increase when Cu2+ is added. Moreover, the cis-2-butene-1,4-diol diisonicotinate shows no increased selectivity when Cu2+ is added. Thus II must be doubly bound to the catalyst and stretched across the catalytic iron center, promoting its reaction and conserving stereochem. A singly binding substrate or one (the isonicotinate) with the wrong geometry cannot use this mechanism. A salen-MnIII epoxidation catalyst has been synthesized carrying bipyridyl appendages that can also bind Cu2. This gives a 43-fold increase in reactivity for the II, compared with an analogous catalyst without the Cu2+ binding sites. In this case the increased reactivity was comparable for III. Furthermore, with this catalyst under all circumstances the cis butene substrate forms ∼7% of trans epoxide. Thus in this more flexible salen system a single binding interaction is chiefly responsible for the increased reactivity of II in the presence of Cu2+, and the second binding group contributes little. The porphyrin catalyst imitates the multipoint substrate binding across a catalytic group characteristic of cytochrome P 450 enzymes.
Journal of the American Chemical Society published new progress about 5205-11-8. 5205-11-8 belongs to esters-buliding-blocks, auxiliary class Alkenyl,Benzene,Ester, name is 3-Methylbut-2-en-1-yl benzoate, and the molecular formula is C12H14O2, Recommanded Product: 3-Methylbut-2-en-1-yl benzoate.
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https://en.wikipedia.org/wiki/Ester,
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