Herein, we introduce
α-nitro-α,β-unsaturated ketones as efficient electrophilic
acyl transfer reagents, and they were employed in Friedel–Crafts
as well as in Michael reactions. The desired acyl transfer products
of these reactions were obtained in high yields with high to excellent
enantioselectivities with t-leucine-derived squaramide
catalyst under mild reaction conditions. Few applications including
a synthesis of the isoxazoline motif have been demonstrated.
The
first organocatalytic asymmetric synthesis of spirooxindole
embedded oxazolidines has been developed via a domino reaction involving
hemiaminal formation, followed by an unprecedented aza-Michael reaction
between isatin derived N-Boc ketimines and γ-hydroxy
enones. A quinine derived bifunctional squaramide catalyst was found
to be efficient for this reaction, and the products were obtained
in good diastereoselectivity and with high enantioselectivity.
The
first organocatalytic asymmetric addition of aromatic α-cyanoketones
to in situ-generated o-quinone methides
has been developed. The products 3,4-dihydrocoumarin and tetrasubstituted
chroman were obtained via addition of aromatic α-cyanoketones
to in situ-generated o-quinone methides
followed by treatment with 0.7 N HCl. With 10 mol % catalyst, the
desired products were obtained in high enantio- and diastereoselectivities.
An organocatalytic asymmetric Michael/acyl transfer reaction between α-nitroketones and 4-arylidenepyrrolidine-2,3-diones is reported. A bifunctional thiourea catalyst was found to be effective for this reaction. With 10 mol % of the catalyst, good results were attained for a variety of 1,5-dihydro-2H-pyrrol-2-ones under mild reaction conditions.
Herein we disclose a catalytic asymmetric dearomatization reaction of β‐naphthols with 4‐aryl‐1,2,4‐triazole‐3,5‐diones. A chiral phosphoric acid with spiro motif was found to be effective for this reaction. The chiral urazole embedded naphthalenones having both axial and central chirality were obtained in good to high yields (70–85%) with high diastereo‐ and enantioselectivities (>20:1, 8–96% ees), having C−N rotational energy barrier 31.54 K.Cal.mol−1 and t1/225 °C=589.8 years. The scope of the reaction was broad and few applications including a bromo‐amination reaction have been demonstrated.
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