Unsymmetrical Saturated Ketones Resulting from Activations of Hydrocarbon C(sp3)鈥揌 and C(sp2)鈥揌 Bonds Effected by Cp*W(NO)(H)(畏3-allyl) Complexes

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• 作者：Rhett A. Baillie ; Guillaume P. Lef猫vre ; Russell J. Wakeham ; Aaron S. Holmes ; Peter Legzdins
• 刊名：Organometallics
• 出版年：2015
• 出版时间：August 24, 2015
• 年：2015
• 卷：34
• 期：16
• 页码：4085-4092
• 全文大小：465K
• ISSN：1520-6041

文摘

C鈥揌 activations of a C(sp²)鈥揌 bond in benzene or a C(sp³)鈥揌 bond in mesitylene at 80 掳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)(畏³-CH₂CHCMe₂) (1), Cp*W(NO)(H)(畏³-CH₂CHCHMe) (2), and Cp*W(NO)(H)(畏³-CH₂CHCHPh) (3) (Cp* = 畏⁵-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 畏²-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)(畏²-CH₂鈺怌HCHMe₂) and Cp*W(NO)(畏²-MeCH鈺怌HPh) 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)(畏²-CH₂鈺怌HCHMe₂) (10) and Cp*W(NO) (CO)(畏²-MeCH鈺怌HPh) (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鈥揅 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鈥?b>3 in three steps via Cp*W(NO)Cl₂.