Palladium-catalyzed α,β-dehydrogenation of acyclic ester equivalents promoted by a novel electron deficient phosphinooxazoline ligand
作者:Tyler J. Fulton、Brenda Wu、Eric J. Alexy、Haiming Zhang、Brian M. Stoltz
DOI:10.1016/j.tet.2019.05.065
日期:2019.8
phosphinooxazoline (PHOX) ligand. The reaction proceeds from the Z-enol carbonate to provide dehydrogenation products exclusively in high E/Z selectivity, while the E-enol carbonate provides the α-allylation product with only minor dehydrogenation. The reaction proceeds with a broad scope of Z-enol carbonates derived from N-acyl indoles to furnish acyclic formal α,β-unsaturated ester equivalents.
N-Heterocyclic Carbene-Mediated Enantioselective Addition of Phenols to Unsymmetrical Alkylarylketenes
作者:Carmen Concellón、Nicolas Duguet、Andrewâ D. Smith
DOI:10.1002/adsc.200900538
日期:2009.11
Chiral N-heterocyclic carbenes (NHCs) mediate the enantioselectiveaddition of 2-phenylphenol to unsymmetricalalkylarylketenes, delivering α-alkyl-α-arylacetic acid derivatives with good levels of enantiocontrol (up to 84% ee). Enantiodivergent stereochemical outcomes are observed using 2-phenylphenol and benzhydrol in the NHC-promoted esterification reaction using a triazolium precatalyst derived
Stereo‐ and Chemodivergent NHC‐Promoted Functionalisation of Arylalkylketenes with Chloral
作者:James J. Douglas、Gwydion Churchill、Alexandra M. Z. Slawin、David J. Fox、Andrew D. Smith
DOI:10.1002/chem.201503308
日期:2015.11.9
Stereo‐ and chemodivergent enantioselective reaction pathways are observed upon treatment of alkylarylketenes and trichloroacetaldehyde (chloral) with N‐heterocyclic carbenes, giving selectively either β‐lactones (up to 88:12 dr, up to 94 % ee) or α‐chloroesters (up to 94 % ee). Either 2‐arylsubstitution or an α‐branched iPr alkyl substituent within the ketene favours the chlorination pathway, allowing
NHC-Promoted Asymmetric β-Lactone Formation from Arylalkylketenes and Electron-Deficient Benzaldehydes or Pyridinecarboxaldehydes
作者:James Douglas、James E. Taylor、Gwydion Churchill、Alexandra M. Z. Slawin、Andrew D. Smith
DOI:10.1021/jo4003079
日期:2013.4.19
A chiral NHCcatalyzes the asymmetric formal [2 + 2] cycloaddition of alkylarylketenes with both electron-deficient benzaldehydes and 2- and 4-pyridinecarboxaldehydes to generate stereodefined β-lactones. In the benzaldehyde series, optimal product diastereo- and enantiocontrol is observed using 2-nitrobenzaldehyde (up to 93:7 dr (syn:anti) and 93% ee). Substituted 2- and 4-pyridinecarboxaldehydes
Lewis Acid-Promoted Ketene–Alkene [2 + 2] Cycloadditions
作者:Christopher M. Rasik、M. Kevin Brown
DOI:10.1021/ja3103007
日期:2013.2.6
are the first examples of ketene-alkene [2 + 2] cycloadditions promoted by Lewis acids. Notable features of this method include (1) substantial rate acceleration relative to traditional thermal reactions, (2) good diastereoselectivities and yields for the formation of the cyclobutanone products, and (3) inverse diastereoselectivity compared with related thermal cycloadditions for many examples. These