Synthesis and Basicity Studies of Quinolino[7,8‑h]quinoline Derivatives

Quinolino­[7,8-h]­quinoline is a superbasic compound, with a pK aH in acetonitrile greater than that of 1,8-bis­(dimethylaminonaphthalene) (DMAN), although its synthesis and the synthesis of its derivatives can be problematic. The use of halogen derivatives 4,9-dichloroquinolino­[7,8-h]­quinoline (1...

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Published in:Journal of organic chemistry 2020-09, Vol.85 (17), p.11297-11308
Main Authors: Rowlands, Gareth J, Severinsen, Rebecca J, Buchanan, Jenna K, Shaffer, Karl J, Jameson, Heather T, Thennakoon, Nishani, Leito, Ivo, Lõkov, Märt, Kütt, Agnes, Vianello, Robert, Despotović, Ines, Radić, Nena, Plieger, Paul G
Format: Article
Language:English
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Summary:Quinolino­[7,8-h]­quinoline is a superbasic compound, with a pK aH in acetonitrile greater than that of 1,8-bis­(dimethylaminonaphthalene) (DMAN), although its synthesis and the synthesis of its derivatives can be problematic. The use of halogen derivatives 4,9-dichloroquinolino­[7,8-h]­quinoline (16) and 4,9-dibromoquinolino­[7,8-h]­quinoline (17) as precursors has granted the formation of a range of substituted quinolinoquinolines. The basicity and other properties of quinolinoquinolines can be modified by the inclusion of suitable functionalities. The experimentally obtained pK aH values of quinolino­[7,8-h]­quinoline derivatives show that N 4,N 4,N 9,N 9-tetraethylquinolino­[7,8-h]­quinoline-4,9-diamine (26) is more superbasic than quinolino­[7,8-h]­quinoline. Computationally derived pK aH values of quinolinoquinolines functionalized with dimethylamino (NMe2), 1,1,3,3-tetramethylguanidino (NC­(NMe2)2) or N,N,N′,N′,N″,N″-hexamethylphosphorimidic triamido (NP­(NMe2)3) groups are significantly greater than those of quinolino­[7,8-h]­quinoline. Overall, electron-donating functionalities are observed to increase the basicity of the quinolinoquinoline moiety, while the substitution of electron-withdrawing groups lowers the basicity.
ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.0c01428