Highly enantioselective [3+2] annulation of isatin-derived MBH-carbonates and 3-nitroindoles was achieved by a chiral DMAP-thiourea bifunctional catalyst.
A novel chiral DMAP–thiourea bifunctional catalyst has been prepared and applied in the highly enantioselective Steglich and Black rearrangement reactions.
Exploration
of the diastereodivergent synthesis of spirocyclic
oxindoles has been challenging. Herein we report asymmetric [3 + 2]
annulations of isatin-derived Morita–Baylis–Hillman
(MBH) carbonates and 5-alkenylthiazol-4(5H)-ones.
Interestingly, two different chiral catalysts, amide-phosphine and
4-dimethylaminopyridine (DMAP)-thiourea, could lead to two kinds of
diastereomeric dispiro oxindoles with three contiguous stereogenic
centers. The hexafluoroisopropanol (HFIP) additive plays a vital role
in accelerating the reaction and tuning the diastereoselectivity.
Moreover, both annulation adducts could be further converted to structurally
diverse spirooxindoles.
Naphthalimides
have found extensive applications in materials science
and pharmaceuticals. It is still highly desirable to develop efficient
methods for the synthesis of naphthalimides with structural diversity.
In this work, we developed a new approach for the synthesis of naphthalimides
via a tandem reaction of o-methylbenzaldehydes and
maleimides. The tandem reaction involves Pd(II)-catalyzed benzylic
C(sp3)–H oxidation using an amino acid as the transient
directing group and Diels–Alder reaction. The subsequent dehydration
forms naphthalimides. The reaction introduces the imide moiety and
constructs a benzene ring simultaneously, allowing for easy access
to a range of naphthalimides with a variety of substituents.
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