Regioselektiv funktionalisierte Pyridine aus nachhaltigen Ressourcen

Abstract

Aus erneuerbaren Quellen – Alkoholen und 1,3‐Aminoalkoholen – werden in einer Ir‐katalysierten dehydrierenden Kondensation regioselektiv Pyridine aufgebaut. Die Methode eröffnet einen leichten Zugang zu unsymmetrisch substituierten Pyridinen bei hoher Verträglichkeit mit funktionellen Gruppen. Es werden drei Äquivalente H2 pro gebildetes Pyridinfragment freigesetzt, und die eingesetzten Alkohole werden vollständig desoxygeniert.

Chemical Exchange Saturation Transfer (CEST) Agents: Quantum Chemistry and MRI

“…Deshalb bietet deren intermediäre dehydrogenierende Aktivierung zu Aldehyden und Ketonen Perspektiven, um petrochemische Vorstufen zu ersetzen. So katalysiert ein Iridiumkomplex basierend auf einem dreizähnigen Pinzettenliganden die dehydrogenierende Kondensation von substituierten Ethanolen mit substituierten 3‐Aminopropanolen zu regioselektiv funktionalisierten Pyridinen (Abbildung 38) 98.…”

New Iridium Catalysts for the Selective Alkylation of Amines by Alcohols under Mild Conditions and for the Synthesis of Quinolines by Acceptor‐less Dehydrogenative Condensation

“…[17] In this regard, an environmentally benign access to unsymmetrically substituted N-heteroaromatic compounds [18] has been reported by the groups of Beller, [19] Milstein, [20] Saito [21] and us. [22] Herein, we report on a new family of catalysts that are able to mediate both HA/BH and ADC reactions. The alkylation of amines was accomplished under very mild conditions (HA/BH) and the ADC concept was used to synthesise quinolones from alcohols and amino alcohols.…”

Iron‐Catalyzed α‐Alkylation of Ketones with Alcohols

“…[17] Following the general hydrogen-borrowing concept, our iron-catalyzed method allows also for the synthesis of quinoline derivatives.B ased on the classic Friedländer annulation reaction, quinolines can be prepared in astraightforward manner from 2-aminobenzaldehyde and various ketones. Using the more stable 2-aminobenzyl alcohol in the presence of ac atalytic amount of base under hydrogen-borrowing conditions is an advantage to perform this reaction [19] compared to reactions in the presence of stoichiometric amounts of base. Using the more stable 2-aminobenzyl alcohol in the presence of ac atalytic amount of base under hydrogen-borrowing conditions is an advantage to perform this reaction [19] compared to reactions in the presence of stoichiometric amounts of base.…”

“…1(2) Cs 2 CO 3 (10) 24 61 29 8 [c] 1 (2) Cs 2 CO 3 (10) 24 74 20 9 [c] 2 (2) Cs 2 CO 3 (10) 24 44 10 10 [c,d] 1 (2) Cs 2 CO 3 (10) 24 80 6 11 [c,e] Entry t [h] NMR-yield [b] (Isolated) [c] 5 [%] alcohol derivatives.C onsequently,a lcohols with both electron-donating (Table 2, entries 11, 12, 16) and electron-withdrawing substituents ( Table 2, entries 13 -15, 21) gave the corresponding a-alkylated ketones in 51-62 %y ields of isolated product. Furthermore,b io-based and synthetically more interesting alcohols such as butan-1-ol and 3-phenylpropan-1-ol could be used, and led to the corresponding ketones in 55 and 42 %y ields of isolated products,r espectively ( Table 2, entries [19][20]. Methanol was unfortunately not suitable for this transformation, probably owing to the more difficult dehydrogenation reaction of this alcohol.…”