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Unsymmetrical Saturated Ketones Resulting from Activations of Hydrocarbon C(sp3)–H and C(sp2)–H Bonds Effected by Cp*W(NO)(H)(η3-allyl) Complexes
Organometallics, Volume: 34, Issue: 16, Pages: 4085 - 4092
Swansea University Author:
Russell Wakeham
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DOI (Published version): 10.1021/acs.organomet.5b00537
Abstract
C–H activations of a C(sp2)–H bond in benzene or a C(sp3)–H bond in mesitylene at 80 °C under CO pressure in undried solvents without rigorous exclusion of air and moisture can be effected with the 18e complexes Cp*W(NO)(H)(η3-CH2CHCMe2) (1), Cp*W(NO)(H)(η3-CH2CHCHMe) (2), and Cp*W(NO)(H)(η3-CH2CHCH...
| Published in: | Organometallics |
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| ISSN: | 0276-7333 1520-6041 |
| Published: |
American Chemical Society (ACS)
2015
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa32708 |
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| Abstract: |
C–H activations of a C(sp2)–H bond in benzene or a C(sp3)–H bond in mesitylene at 80 °C under CO pressure in undried solvents without rigorous exclusion of air and moisture can be effected with the 18e complexes Cp*W(NO)(H)(η3-CH2CHCMe2) (1), Cp*W(NO)(H)(η3-CH2CHCHMe) (2), and Cp*W(NO)(H)(η3-CH2CHCHPh) (3) (Cp* = η5-C5Me5). These activations are regiospecific and afford in the case of complex 1 good yields of the unsymmetrical saturated ketones 4-methyl-1-phenylpentan-1-one (5) and 1-(3,5-dimethylphenyl)-5-methylhexan-2-one (8), respectively, in which the alkyl groups result from hydrogenation of the allyl ligand in the organometallic reactant. Complex 2 reacts similarly, but complex 3 only produces the ketone from its reaction with CO in benzene. Theoretical calculations indicate that the key mechanistic feature of these conversions is the formation of a 16e η2-alkene complex which is generated by the regiospecific migration of the hydride ligand onto the tertiary carbon of the allyl ligand. The 16e Cp*W(NO)(η2-CH2═CHCHMe2) and Cp*W(NO)(η2-MeCH═CHPh) intermediate complexes formed in this manner by complexes 1 and 3, respectively, have been trapped as the corresponding 18e CO adducts Cp*W(NO) (CO)(η2-CH2═CHCHMe2) (10) and Cp*W(NO) (CO)(η2-MeCH═CHPh) (11). All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of two isomers of 11 have been established by single-crystal X-ray crystallographic analyses. This new and facile method of synthesizing saturated unsymmetrical ketones via C–C bond formation not only is atom economical but also is part of a complete synthetic cycle, since Cp*W(NO)(CO)2 (4) is the final organometallic product formed in all cases, and it can be readily reconverted to the hydrido allyl reactants 1–3 in three steps via Cp*W(NO)Cl2. |
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| College: |
Faculty of Science and Engineering |
| Issue: |
16 |
| Start Page: |
4085 |
| End Page: |
4092 |