This study presents a straightforward [3 + 2] annulation method for synthesizing bisspiro(oxindole) derivatives using isatin‐derived Morita–Baylis–Hillman carbonates and p‐quinone methides (p‐QMs) with 4‐dimethylaminopyridine (DMAP) as the catalyst. The optimized protocol in dichloromethane (DCM) solvent achieves good yields (up to 87%) and diastereoselectivity (>20:1). The method's versatility is shown through the synthesis of various derivatives, including chiral variants with up to 82% ee. The intermediates were captured by HRMS, and a plausible reaction pathway was proposed.
Enantioselective Michael Addition to α,β-Unsaturated Aldehydes: Combinatorial Catalyst Preparation and Screening, Reaction Optimization, and Mechanistic Studies
作者:Ivana Fleischer、Andreas Pfaltz
DOI:10.1002/chem.200902449
日期:2010.1.4
Shortcut to chiral catalysts: An efficient combinatorial strategy based on back reaction screening by ESI‐MS allows rapid evaluation of organocatalysts for the asymmetric Michael addition to α,β‐unsaturated aldehydes (see scheme). An unexpected nonlinear effect has been observed in this reaction, resulting from a double nucleophilic–electrophilic activation mechanism involving two catalyst molecules
The enantioselective aminocatalytic α-chlorination of aldehydes is a challenging reaction because of its tendency to proceed through neutral intermediates in unselective pathways. Herein we report the rational shift to a highly selective reaction pathway involving charged intermediates using hexafluoroisopropanol as solvent. This change in mechanism has enabled us to match and improve upon the yields
作者:Samantha N. Rokey、Justin A. Simanis、Chunyin M. Law、Shilpa Pohani、Samantha Willens Behrends、Jacob J. Bulandr、Gregory M. Ferrence、John R. Goodell、T. Andrew Mitchell
DOI:10.1016/j.tetlet.2020.152377
日期:2020.10
Intramolecular oxidopyrylium-based [5 + 2] cycloadditions utilizing chiral auxiliaries were investigated. Both acetoxypyranones and silyloxypyrones were employed and sulfinimines, oxazolidinones, hydrazones, and chiral enamines were explored. Carbonyl-based auxiliaries gave low selectivity, but enamines afforded excellent diastereoselectivity. Overall, facial selectivity varied significantly providing
KAHA Ligations That Form Aspartyl Aldehyde Residues as Synthetic Handles for Protein Modification and Purification
作者:Claudia E. Murar、Frédéric Thuaud、Jeffrey W. Bode
DOI:10.1021/ja511231f
日期:2014.12.31
semialdehyde (Asa) side chain can be easily prepared by a chemoselective amide-formingligation that results in the formation of the Asa residue at the ligation site. This strategy employs the α-ketoacid-hydroxylamine (KAHA) ligation in combination with a new isoxazolidine monomer that forms a side-chain aldehyde upon ligation. This monomer is easily prepared on a preparative scale by a catalytic, enantioselective