Topic
Annulation
About: Annulation is a research topic. Over the lifetime, 10152 publications have been published within this topic receiving 189701 citations.
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TL;DR: The first enantioselective annulation of α-arylidene pyrazolones through a formal C(sp3 )-H activation under mild conditions enabled by highly variable RhIII -Cpx catalysts is reported.
Abstract: Herein, we report the first enantioselective annulation of α-arylidene pyrazolones through a formal C(sp3 )-H activation under mild conditions enabled by highly variable RhIII -Cpx catalysts. The method has a wide substrate scope and proceeds with good to excellent yields and enantioselectivities. Its synthetic utility was demonstrated by the late-stage functionalization of drugs and natural products as well as the preparation of enantioenriched [3]dendralenes. Preliminary biological investigations also identified the spiropyrazolones as a novel class of Hedgehog pathway inhibitors.
88 citations
TL;DR: The Rh(III)-catalyzed regioselective C2-H bond carbenoid insertion/cyclization of N-amidoindoles with α-acyl diazo compounds has been developed and provides a novel approach to 2H-pyrimido[1,6-a]indol-1-ones with a broad range of functional group tolerance.
87 citations
TL;DR: An efficient, sterocontrolled entry to the dioxabicyclo[3.3.0] octane ring system of (±)-kumausalkene has been developed as discussed by the authors.
Abstract: An efficient, sterocontrolled entry to the dioxabicyclo[3.3.0]octane ring system of (±)-kumausalkene has been developed. This synthesis buids upon our general strategy for preparing C 15 halogenated tetrahydrofuranoid marine lipids using the ring-enlarging tetrahydrofuran annulation of cyclic, allylic diols as the central step. A key intermediate, hydrobenzofuranone 8, is available with complete sterocontrol form the Lewis acid-catalized condensation of 1-vinylcyclopentanediol (4) and α-(benzoyloxy)acetaldehyde (Scheme II)
87 citations
TL;DR: The metal-free [2 + 2 + 1] annulation of alkynes, nitriles, and O-atoms for the regioselective assembly of 2,4,5-trisubstituted oxazole compounds has been achieved by the use of PhIO with TfOH or Tf2NH.
87 citations
TL;DR: This study describes the application of chiral phosphepine catalysts to address the challenge of providing access to useful scaffolds that are found in bioactive compounds, including diquinane and quinolin-2-one derivatives, with very good stereoselectivity.
Abstract: Substantial progress has been described in the development of asymmetric variants of the phosphine-catalyzed intermolecular [3+2] annulation of allenes with alkenes; however, there have not been corresponding advances for the intramolecular process, which can generate a higher level of complexity (an additional ring and stereocenter(s)). In this study, we describe the application of chiral phosphepine catalysts to address this challenge, thereby providing access to useful scaffolds that are found in bioactive compounds, including diquinane and quinolin-2-one derivatives, with very good stereoselectivity. The products of the [3+2] annulation can be readily transformed into structures that are even more stereochemically rich. Mechanistic studies are consistent with β addition of the phosphepine to the allene being the turnover-limiting step of the catalytic cycle, followed by a concerted [3+2] cycloaddition to the pendant olefin.
87 citations