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Regio- and stereoselectivity of polar [2+3] cycloaddition reactions between (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone and selected (E)-2-substituted nitroethenes

100%

Jasiński R., Ziółkowska M., Demchuk O., Maziarka A.

Open Chemistry

2014

vol. 12

issue 5

586-593

[2+3] Cycloaddition reactions of the highly reactive (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone with (E)-2-R-nitroethenes proceed under mild conditions and yield mixtures of stereoisomeric 2-methyl-3-(3,4,5-trimethoxyphenyl)-4-nitro-5-R-isoxazolidines. The effect of regiospecificity of the cycloadditions may be accounted for by the theory of electrophilicity indexes. Stereoselectivity, however, is determined by a compilation of steric and secondary orbital effects.

Addition of boranes to (E)-(η5-C5H5)2Zr(CH=CHPh)Cl

100%

Ferland P., Prosser K., Bourque J., Edwards I., Hamilton N., Joyce L., Finniss M., Yorke S., Vogels C., Fontaine F.-G., Decken A., Westcott S.

Open Chemistry

2013

vol. 11

issue 5

811-816

In this study, the addition of boranes to (E)-(η5-C5H5)2Zr(CH=CHPh)Cl (3) has been examined in order to investigate the regioselectivity of these ‘hydroboration’ reactions. We have found that these additions proceed with remarkable selectivity to give exclusive formation of a saturated organic molecule where one carbon atom has both the boron and the zirconium fragments. These reactions do not proceed via a conventional hydroboration reaction, but instead go through an initial transmetalation step to generate (E)-(η5-C5H5)2Zr(H)Cl (1) and the corresponding alkenyl boron intermediate, whereupon subsequent hydrozirconation of this latter species gives the geminal products. An x-ray diffraction study has been conducted on gem-(η5-C5H5)2Zr(CH(Bpin)CH2Ph)Cl (pin = 1, 2-O2C2Me4) (2). Crystals of 2 were orthorhombic with a = 18.545(3) Å, b = 15.713(3) Å, c = 16.157(3) Å in the space group Pccn. An x-ray diffraction study has also been conducted on the trinuclear zirconium oxide species (η5-C5H5)2ZrO2[ZrCl(η5-C5H5)2]2(4). Crystals of 4 were orthorhombic with a = 13.6000(8) Å, b = 14.2252(8) Å, c = 17.6500(10) Å in the space group P2(1)2(1)2(1). [...]

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2 Open Chemistry

1 2014

1 2013

1 Bourque J.

1 Decken A.

1 Demchuk O.

1 Edwards I.

1 Ferland P.

1 Finniss M.

1 Fontaine F.-G.

1 Hamilton N.

1 Jasiński R.

1 Joyce L.

1 Maziarka A.

1 Prosser K.

1 Vogels C.

1 Westcott S.

1 Yorke S.

1 Ziółkowska M.

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Regio- and stereoselectivity of polar [2+3] cycloaddition reactions between (Z)-C-(3,4,5-trimethoxyphenyl)-N-methylnitrone and selected (E)-2-substituted nitroethenes

Addition of boranes to (E)-(η5-C5H5)2Zr(CH=CHPh)Cl