The
reaction of vinylsulfonamides with donor–acceptor carbenes
derived from α-aryldiazoesters, catalyzed by the tert-butyl glycine-derived dirhodium complex Rh2(S-4-Br-NTTL)4, has been reported. This method provides
a variety of α-aryl-β-aminocyclopropane carboxylic acid
derivatives bearing one quaternary carbon stereogenic center vicinal
to the amino-substituted carbon in high yields with excellent diastereo-
and enantioselectivities. Vinylsulfonamides showed complementary advantages
over the well-developed vinylamides or vinylcarbamates for this Rh(II)-catalyzed
cyclopropanation strategy. Moreover, these conformationally restricted
α-aryl-β-aminocyclopropyl carboxylic acid derivatives
can be readily incorporated into dipeptides.
Reported herein is a catalyst-controlled reaction of imidazolidines with allenes, providing a general and efficient method to construct two series of N-heterocycles, 1,4-diazepanes via gold-catalyzed [5 + 2] cycloadditions and 1,4diazabicyclo[4.3.1]decanes through iron-catalyzed [5 + 2] cycloaddition/Friedel−Crafts cyclization cascades, in moderate to high yields under mild reaction conditions. Mechanistic investigations indicate that water acts as a proton shuttle to assist the [1,3]-hydrogen shift in the Friedel−Crafts cyclization process. This strategy features the use of imidazolidines as stable 1,5-dipoles for [5 + 2] cycloadditions and the utilization of an iron catalyst to accomplish the [5 + 2] cycloaddition/Friedel−Crafts cyclization cascades in a highly diastereoselective manner for the synthesis of bridged-ring systems.
An N-heterocyclic carbene (NHC) catalyzed asymmetric [3 + 3] annulation of α-bromoenals with 5-aminopyrazoles is described. Using the established methodology, a structurally diverse set of high value dihydropyrazolo[3,4-b]pyridine-6ones were efficiently constructed in high yields (up to 99%) with excellent enantioselectivities (up to > 99%). The easily available starting materials, broad substrate scope, mild reaction conditions, excellent yield and enantioselectivity make this strategy attractive for the asymmetric construction of pyrazolo-fused pyridone derivatives.
Reported herein are the unprecedented copper-catalyzed formal [n + 1]/[n + 3] (n = 5, 6) cycloadditions of diazo compounds with imidazolidines/hexahydropyrimidines, thus providing a general, economical, and efficient route to construct different sized (six-to nine-membered) diaza-heterocycles in moderate to excellent yields under mild reaction conditions. This strategy features the use of copper catalyst to accomplish such diverse annulations and the utilization of imidazolidines/ hexahydropyrimidines as stable 1,5-/1,6-dipoles.
Saturated 1,4-diazocanes are highly important for medicinal
chemistry
and drug discovery, but their syntheses are often tedious. Herein,
we report a copper-catalyzed (5 + 3) annulation of donor–acceptor
cyclopropanes with imidazolidines, thereby providing a straightforward
method to access a library of saturated 1,4-diazocanes in moderate
to excellent yields under mild reaction conditions. More importantly,
the asymmetric version of this (5 + 3) annulation leading to optically
active saturated 1,4-diazocanes is achieved by two strategies: (i)
chirality transfer and (ii) dynamic kinetic asymmetric transformation
by employing copper triflate with an SaBOX ligand. In addition, the
analogous (6 + 3) annulation of donor–acceptor cyclopropanes
with hexahydropyrimidines is also realized.
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