Merging Chiral Brønsted Acid/Base Catalysis: An Enantioselective [4 + 2] Cycloaddition of <i>o</i>-Hydroxystyrenes with Azlactones
作者:Yu-Chen Zhang、Qiu-Ning Zhu、Xue Yang、Lu-Jia Zhou、Feng Shi
DOI:10.1021/acs.joc.6b00078
日期:2016.2.19
An enantioselective [4 + 2] cycloaddition of o-hydroxylstyrenes with azlactones has been established by merging chiralBrønstedacid (chiral phosphoric acid) and base (chiral guanidine) catalysis, which constructed a biologically important dihydrocoumarin scaffold in an efficient and enantioselective style (up to 99% yield, 96:4 er). This approach has not only realized the successful application of
Practical, Large-Scale Preparation of Benzoxepines and Coumarins through Rhodium(III)-Catalyzed C–H Activation/Annulation Reactions
作者:Moisés Gulías、Daniel Marcos-Atanes、José L. Mascareñas、Marc Font
DOI:10.1021/acs.oprd.9b00191
日期:2019.8.16
Herein we disclose the assembly of benzoxepines and coumarins from 2-alkenylphenol precursors using [Cp*RhCl2]2 as the precatalyst and alkynes or carbon monoxide as reacting partners. The preparation of benzoxepines and coumarins can be scaled up to 33 mmol using low catalyst loadings.
OH-Directed Alkynylation of 2-Vinylphenols with Ethynyl Benziodoxolones: A Fast Access to Terminal 1,3-Enynes
作者:Peter Finkbeiner、Ulrich Kloeckner、Boris J. Nachtsheim
DOI:10.1002/anie.201412148
日期:2015.4.13
The first direct alkynylation of 2‐vinylphenols was developed. The rationally optimized hypervalent iodine reagent TIPS‐EBX* in combination with [(Cp*RhCl2)2] as a CH‐activating transition metal catalyst enables the construction of a variety of highly substituted 1,3‐enynes in high yields of up to 98 %. This novel CH activation method shows excellent chemoselectivity and exclusive (Z)‐stereoselectivity
Palladium(II)-Catalyzed Annulation between <i>ortho</i>-Alkenylphenols and Allenes. Key Role of the Metal Geometry in Determining the Reaction Outcome
作者:Noelia Casanova、Karina P. Del Rio、Rebeca García-Fandiño、José L. Mascareñas、Moisés Gulías
DOI:10.1021/acscatal.6b00739
日期:2016.5.6
2-Alkenylphenols react with allenes, upon treatment with catalytic amounts of Pd(II) and Cu(II), to give benzoxepine products in high yields and with very good regio- and diastereoselectivities. This contrasts with the results obtained with Rh catalysts, which provided chromene-like products through a pathway involving a β-hydrogen elimination step. Computational studies suggest that the square planar
Rhodium-Catalyzed (5+1) Annulations Between 2-Alkenylphenols and Allenes: A Practical Entry to 2,2-Disubstituted 2<i>H</i>-Chromenes
作者:Noelia Casanova、Andrés Seoane、José L. Mascareñas、Moisés Gulías
DOI:10.1002/anie.201410350
日期:2015.2.16
alkenylphenols react with allenes under rhodiumcatalysis to provide valuable 2,2‐disubstituted 2H‐chromenes. The whole process, which involves the cleavage of one CH bond of the alkenyl moiety and the participation of the allene as a one‐carboncycloaddition partner, can be considered a simple, versatile, and atom‐economical (5+1) heteroannulation. The reaction tolerates a broad range of substituents