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Direct and Enantioselective Vinylogous Michael Addition of α‐Alkylidenepyrazolinones to Nitroolefins Catalyzed by Dual Cinchona Alkaloid Thioureas
Author(s) -
Rassu Gloria,
Zambrano Vincenzo,
Pinna Luigi,
Curti Claudio,
Battistini Lucia,
Sartori Andrea,
Pelosi Giorgio,
Casiraghi Giovanni,
Zanardi Franca
Publication year - 2014
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201300964
Subject(s) - enantioselective synthesis , chemistry , cinchona , nucleophile , electrophile , enantiomer , cinchona alkaloids , michael reaction , adduct , catalysis , annulation , organic chemistry , lewis acids and bases , stereochemistry , combinatorial chemistry
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.