1643536-96-2Relevant academic research and scientific papers
Direct and enantioselective vinylogous michael addition of α-alkylidenepyrazolinones to nitroolefins catalyzed by dual cinchona alkaloid thioureas
Rassu, Gloria,Zambrano, Vincenzo,Pinna, Luigi,Curti, Claudio,Battistini, Lucia,Sartori, Andrea,Pelosi, Giorgio,Casiraghi, Giovanni,Zanardi, Franca
, p. 2330 - 2336 (2014/07/21)
While several protocols exist for the asymmetric functionalization of pyrazolinones at the α-position relying on nucleophilic addition or annulation procedures, use of α-alkylidene electron-rich analogues in asymmetric vinylogous coupling to carbon electrophiles is substantially an uncharted domain. We now report, for the first time, that alkylidenepyrazolinones carrying an enolizable carbon at the γ-position efficiently participate in direct and asymmetric, catalytic vinylogous Michael-type additions to nitroolefins providing the expected adducts in high yields, with complete γ-site selectivity and with extraordinary levels of enantio-, diastereo-, and geometrical selectivities. Both enantiomeric adducts were equally accessed by employing a quasi-enantiomeric quinine- or quinidine-based thiourea catalyst pair.
