Fernández Sáez N, García López J, Iglesias MJ, López Ortiz F. Derivatization of (quinolin-8-yl)phosphinimidic amides via ortho-lithiation revisited.
Dalton Trans 2015;
44:11504-13. [PMID:
26030882 DOI:
10.1039/c5dt01392e]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
5The direct ortho-lithiation of N-H containing (quinolin-8-yl)phosphinimidic amides by reaction with 1 equiv. of n-BuLi described by Wang and co-workers has been re-examined. The multinuclear magnetic resonance ((1)H, (2)H, (7)Li, (13)C, (15)N and (31)P) study of the species formed in the monolithiation of N-(tert-butyl)-P,P-diphenyl-N'-(quinolin-8-yl)phosphinimidic amide 5 with n-BuLi in THF showed that proton abstraction occurred exclusively and quantitatively at the NH. The combination of the NMR results with a DFT study made it possible to describe the structure of the N-lithiated species 9 as a dimer consisting of an eight-membered ring showing two lithium ions triply coordinated to nitrogen atoms corresponding to the deprotonated amine and aminoquinoline moieties of different monomers. The formation of a polymer featuring the same coordination mode couldn't be excluded. In addition, optimized conditions for the efficient derivatization of 5 via ortho-lithiation were realised. The reaction of 5 with 2.4 equiv. of t-BuLi in THF in the temperature range of -80 °C to 25 °C for 3 h afforded a N,C(ortho)-dilithiated species that was trapped with a series of electrophiles leading to new functionalized ortho derivatives of 5 in good yields.
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