ABSTRACT
A tetrasubstituted carbon atom connected by three sp3 or sp2-carbons with single nitrogen, i.e., the α-tertiary amine (ATA) functional group, is an essential structure of diverse naturally occurring alkaloids and pharmaceuticals. The synthetic approach toward ATA structures is intricate, therefore, a straightforward catalytic method has remained a substantial challenge. Here we show an efficient water-accelerated organocatalytic method to directly access ATA incorporating homoallylic amine structures by exploiting readily accessible general ketones as useful starting material. The synergistic action of a hydrophobic Brønsted acid in combination with a squaramide hydrogen-bonding donor under aqueous condition enabled the facile formation of the desired moiety. The developed exceptionally mild but powerful system facilitated a broad substrate scope, and enabled efficient multi-gram scalability.
Subject(s)
Amines , Water , Amines/chemistry , Carbon/chemistry , Catalysis , Molecular Structure , StereoisomerismABSTRACT
A one-pot protocol for the synthesis of 2,3-diarylbenzo[ b]furan derivatives through an N-heterocyclic carbene catalyzed 1,6-conjugate addition of aromatic aldehydes to 2-hydroxyphenyl-substituted para-quinone methides followed by acid-mediated dehydrative annulation has been developed. This protocol allowed us to access a wide range of 2,3-diarylbenzo[ b]furan derivatives in moderate to good yields.
ABSTRACT
An intermolecular Rauhut-Currier reaction between α,ß-unsaturated carbonyl compounds and p-quinone methides has been developed by employing bis(amino)cyclopropenylidene as a catalyst. This protocol allows access to a variety of vinyl diarylmethane derivatives in moderate to good yields.
ABSTRACT
Bis-(amino)cyclopropenylidene has been utilised as a non-covalent Brønsted base catalyst in the 1,6-conjugate addition of carbon nucleophiles to p-QMs. This protocol makes it possible to access unsymmetrical diaryl- and triarylmethanes in good to excellent yields. Further, this catalyst was also explored in the 1,4-conjugate addition of carbon nucleophiles to enone systems.
ABSTRACT
An organocatalytic approach toward α-arylated nitriles using N-heterocyclic carbene (NHC) as a catalyst is described. This protocol comprises an NHC catalyzed activation of Me3Si-CN followed by 1,6-conjugate addition of cyanide to para-quinone methides (p-QMs) and fuchsones leading to α-diaryl- and α-triaryl nitriles in good to excellent yields.
