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 inJournal of organic chemistry Vol. 85; no. 17; pp. 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 Journal Article
LanguageEnglish
Published WASHINGTON American Chemical Society 04.09.2020
Amer Chemical Soc
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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.
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ISSN:0022-3263
1520-6904
DOI:10.1021/acs.joc.0c01428