Sinisi, Alessandro
(2016)
Dearomatizzazione organocatalitica regio- ed enantioselettiva di sali di piridinio attivati.
[Laurea magistrale], Università di Bologna, Corso di Studio in
Chimica industriale [LM-DM270]
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Abstract
In this work, we present the first regio- and enantioselective organocatalytic nucleophilic dearomatization of activated N-alkyl pyridinium salts. In particular, N-benzyl pyridinium bromides bearing electron-withdrawing substituents at the C3 position of the pyridine ring were chosen as substrates. These compounds were easily obtained through an alkylation reaction between benzyl bromides and the corresponding 3-substituted pyridines. Then, a wide range of nucleophiles and organocatalysts was tested, providing the best results when indole, a thiourea derived from quinidine and 1-benzyl-3-nitropyridinum bromide were employed as the nucleophile, the catalyst and the pyridinium salt, respectively. Subsequently, the reaction conditions were optimised evaluating different bases, solvents, N-benzylic protecting groups, molar concentrations and temperatures. With the optimized condition in hand, the scope of the reaction with different substituted indoles was explored, affording the corresponding 1,4-dihydropyridines in good yields, regio- and enantio-selectivities. In addition, several experiments were carried out in order to understand the mechanism of the reaction, showing an unusual pathway involving a covalently bound intermediate formed by addition of the catalyst to the pyridine unit.
Abstract
In this work, we present the first regio- and enantioselective organocatalytic nucleophilic dearomatization of activated N-alkyl pyridinium salts. In particular, N-benzyl pyridinium bromides bearing electron-withdrawing substituents at the C3 position of the pyridine ring were chosen as substrates. These compounds were easily obtained through an alkylation reaction between benzyl bromides and the corresponding 3-substituted pyridines. Then, a wide range of nucleophiles and organocatalysts was tested, providing the best results when indole, a thiourea derived from quinidine and 1-benzyl-3-nitropyridinum bromide were employed as the nucleophile, the catalyst and the pyridinium salt, respectively. Subsequently, the reaction conditions were optimised evaluating different bases, solvents, N-benzylic protecting groups, molar concentrations and temperatures. With the optimized condition in hand, the scope of the reaction with different substituted indoles was explored, affording the corresponding 1,4-dihydropyridines in good yields, regio- and enantio-selectivities. In addition, several experiments were carried out in order to understand the mechanism of the reaction, showing an unusual pathway involving a covalently bound intermediate formed by addition of the catalyst to the pyridine unit.
Tipologia del documento
Tesi di laurea
(Laurea magistrale)
Autore della tesi
Sinisi, Alessandro
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Parole chiave
dearomatizzazione organocatalisi sali di piridinio sintesi asimmetrica indolo
Data di discussione della Tesi
23 Marzo 2016
URI
Altri metadati
Tipologia del documento
Tesi di laurea
(NON SPECIFICATO)
Autore della tesi
Sinisi, Alessandro
Relatore della tesi
Correlatore della tesi
Scuola
Corso di studio
Parole chiave
dearomatizzazione organocatalisi sali di piridinio sintesi asimmetrica indolo
Data di discussione della Tesi
23 Marzo 2016
URI
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