872974-99-7Relevant academic research and scientific papers
Coupling of an aldehyde or ketone to pyridine mediated by a tungsten imido complex
Hayton, Trevor W.,Boncella, James M.,Scott, Brian L.,Abboud, Khalil A.,Mills, Ryan C.
, p. 9506 - 9517 (2008/10/09)
The reactivity of W(NPh)(o-(Me3SiN)2C 6H4)(py)2 and W(NPh)(o-(Me3SiN) 2C6H4)(pic)2 (py = pyridine; pic = 4-picoline) with unsaturated substrates has been investigated. Treatment of W(NPh)(o-(Me3SiN)2C6H4)(py) 2 with diphenylacetylene or 2,3-dimethyl-1,3-butadiene generates W(NPh)(o-(Me3SiN)2C6H4) (η2-PhC≡CPh) (1) and W(NPh)(o-(Me3SiN) 2C6H4)-(η4-CH 2=C(Me)C(Me)=CH2) (3), respectively, while the addition of ethylene to W(NPh)(o-(Me3SiN)2C6H 4)(py)2 generates the known metallacycle W(NPh)(o-(Me 3SiN)2C6H4)(CH2CH 2CH2CH2). The addition of 2 equiv of acetone to W(NPh)(o-(Me3SiN)2C6H4)(pic) 2 provides the azaoxymetallacycle W(NPh)(o-(Me3SiN) 2C6H4)(OCH(Me)2)(OC(Me) 2-o-C5H3N-p-Me) (4), the result of acetone insertion into the ortho C-H bond of picoline. Similarily, the addition of 2 equiv of RC(O)H [R = Ph, tBu] to W(NPh)(o-(Me3SiN) 2C6H4)(py)2 generates W(NPh)(o-(Me3SiN)2C6H4)(OCH 2R)-(OCH(R)-o-C5H4N) [R = Ph, 5; tBu, 6]. In contrast, reaction between W(NPh)(o-(Me 3SiN)2C6H4)(py)2 and 2-pyridine carboxaldehyde yields the diolate W(NPh)(o-(Me3SiN) 2C6H4)(OCH(C5H4N) CH(C5H4N)O) (7). The synthesis of W(NPh)-(o-(Me 3SiN)2C6H4)(PMe3)(py) (η2-OC(H)C6H4-p-Me) (9), formed by the addition of p-tolualdehyde to a mixture of W(NPh)(o-(Me3SiN) 2C6H4)(py)2 and PMe3, suggests that an η2-aldehyde intermediate is involved in the formation of the azaoxymetallacycle, while the isolation of W(NPh)(o-(Me 3SiN)2C6H4)(Cl)(OC(Me)(CMe 3)-o-C5H4N) (10), formed by the reaction of pinacolone with W(NPh)(o-(Me3SiN)2C6H 4)(py)2, in the presence of adventitious CH 2Cl2, suggests that the reaction proceeds via the hydride W(NPh)(o-(Me3SiN)2C6H4)(H)(OC(Me) (CMe3)-o-C5H4N).
