Enantioselective Cycloaddition of Styrenes with Aldimines Catalyzed by a Chiral Magnesium Potassium Binaphthyldisulfonate Cluster as a Chiral Brønsted Acid Catalyst
A chiral magnesium potassium binaphthyldisulfonate cluster, as a chiral Brønsted acid catalyst, was shown to catalyze an enantioselective cycloaddition of styrenes with aldimines for the first time. The strong Brønsted acidity of the catalyst precursors, which might dissolve drying agents and take up the leached Mg2+ and K+, serendipitously led to good enantioselectivity. Mechanistic aspects were supported
Organocatalytic Asymmetric Synthesis of Propargylamines with Two Adjacent Stereocenters: Mannich-Type Reactions of In Situ Generated C-Alkynyl Imines with β-Keto Esters
作者:Taichi Kano、Taiga Yurino、Keiji Maruoka
DOI:10.1002/anie.201304963
日期:2013.10.25
Side by side: The title reaction is catalyzed by the chiral Brønsted acid (S)‐1, and affords hitherto less accessible chiral propargylamines, having twoadjacentstereocenters, in good to excellent diastereo‐ and enantioselectivities. Boc=tert‐butoxycarbonyl.
A Carbodiimide-Mediated P–C Bond-Forming Reaction: Mild Amidoalkylation of <i>P</i>-Nucleophiles by Boc-Aminals
作者:Paraskevi Kokkala、Thayalan Rajeshkumar、Anastasia Mpakali、Efstratios Stratikos、Konstantinos D. Vogiatzis、Dimitris Georgiadis
DOI:10.1021/acs.orglett.1c00155
日期:2021.3.5
carbodiimide-mediated P–C bond-forming reaction is described. The reaction involves activation of β-carboxyethylphosphinic acids and subsequent reaction with Boc-aminals using acid-catalysis. Mechanistic experiments using 31P NMR spectroscopy and DFT calculations support the contribution of unusually reactive cyclic phosphinic/carboxylic mixed anhydrides in a reaction pathway involving ion-pair “swapping”
Triethylborane-mediated tin-freeradical alkylation of N-alkoxycarbonyl-imines, such as N-Boc-, N-Cbz-, and N-Teoc-imines, proceeded smoothly at a low temperature (−78 to −20 °C) to give the corresponding adducts in high yield. Although the formation of isocyanate was the major unfavorable reaction at room temperature, a one-pot conversion of N-Boc-imine to N-ethoxycarbonyl-adduct was possible through
Crafty aminals: The in situgeneration of hitherto unattainable alkynyl‐substituted N‐Boc‐protected imines was realized by the acid‐catalyzed elimination of tert‐butyl carbamate from N‐Boc aminals. A wide variety of N‐Boc imines can be generated, which can then be utilized for subsequent carbon–carbon bond‐forming reactions, such as Mannich‐type reactions.