An unprecedented enantioselective intramolecular oxa-Michael reaction of enols has been described. A squaramide-containing tertiary amine based bifunctional organocatalyst efficiently activates the o-homoformyl chalcones to provide the chiral isochromenes in moderate yields and good to excellent enantioselectivities. Further, late-stage functionalizations of the vinyl ether moiety of the chiral isochromene products have also been exemplified.
Aliphatic, aromatic, and heteroaromatic aldehydes were readily converted to corresponding nitriles in a one‐pot reaction sequence with hydroxylamine and sulfuryl fluoride. The reaction proceeds at room temperature, does not require metal catalysts and special precautions, and produces nitriles in excellent yields. It is compatible with a variety of functional groups, can be performed in aqueous and organic solvents, and is readily scalable to multigram quantities. Mild conditions and high selectivity of the reaction enabled the construction of polyfunctional probes containing nitrile, alkyne, azide, and fluorosulfate groups for further orthogonal derivatization.
A metal‐free and redox‐neutral method for Beckmann rearrangement employing inexpensive and readily available SO2F2 gas is described. The reported transformation proceeds at ambient temperature and is compatible with a wide range of sterically and electronically diverse aromatic, heteroaromatic, aliphatic and lignin‐like oximes providing amides in good to excellent yields. The reaction proceeds through the formation of an imidoyl fluoride intermediate that can also be used for the synthesis of amidines.
An enantioselective intramolecular oxa‐Michael reaction of enols catalyzed by a squaramide‐containing tertiary amine based bifunctional organocatalyst, which efficiently activates the o‐homoformyl chalcones, provides chiral isochromenes in moderate yields and good to excellent enantioselectivities.
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