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Issue 29, 2017
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Borata-Wittig olefination reactions of ketones, carboxylic esters and amides with bis(pentafluorophenyl)borata-alkene reagents

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Abstract

The strongly electrophilic borane derivative amino–CH2CH2CH2–B(C6F5)26 was α-CH deprotonated with LiTMP to give the borata-alkene {[amino–(CH2)2–CH[double bond, length as m-dash]B(C6F5)2][Li+]}29 which underwent facile [2 + 2] cycloaddition reactions with benzophenone or fluorenone to yield the respective 1,2-oxaboretanides 11a,b. Compounds 9 and 11 were characterized by the X-ray diffraction. Thermolysis or hydrolysis of compounds 11a,b gave the corresponding borata-Wittig olefination products 12a,b. A variety of R–CH2–CH2–B(C6F5)2 boranes (conveniently generated by hydroboration of terminal alkenes R–CH[double bond, length as m-dash]CH2 with Piers’ borane [HB(C6F5)2]) were analogously deprotonated to give the respective borata-alkenes 16a–e (R: Ph–CH2–, nC4H9, tBu, Cy, PhCH2CH2–). They underwent “non-classical” borata-Wittig olefination reactions with ethylformate to give the respective enolether carbonylation products, or their C1-elongated aldehydes (after hydrolysis). The borata-alkene [Ph–(CH2)2–CH[double bond, length as m-dash]B(C6F5)2] [Li+HTMP] (16a) gave the respective “non-classical” borata-Wittig olefination products, the enolethers 25a,b and 27, respectively, upon treatment with methyl- or ethyl acetate or γ-butyrolactone.

Graphical abstract: Borata-Wittig olefination reactions of ketones, carboxylic esters and amides with bis(pentafluorophenyl)borata-alkene reagents

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Publication details

The article was received on 23 May 2017, accepted on 30 Jun 2017 and first published on 30 Jun 2017


Article type: Paper
DOI: 10.1039/C7OB01591G
Citation: Org. Biomol. Chem., 2017,15, 6223-6232
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    Borata-Wittig olefination reactions of ketones, carboxylic esters and amides with bis(pentafluorophenyl)borata-alkene reagents

    T. Wang, S. Kohrt, C. G. Daniliuc, G. Kehr and G. Erker, Org. Biomol. Chem., 2017, 15, 6223
    DOI: 10.1039/C7OB01591G

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