76896-96-3Relevant academic research and scientific papers
Base-free Enantioselective C(1)-Ammonium Enolate Catalysis Exploiting Aryloxides: A Synthetic and Mechanistic Study
McLaughlin, Calum,Slawin, Alexandra M. Z.,Smith, Andrew D.
supporting information, p. 15111 - 15119 (2019/11/05)
An isothiourea-catalyzed enantioselective Michael addition of aryl ester pronucleophiles to vinyl bis-sulfones via C(1)-ammonium enolate intermediates has been developed. This operationally simple method allows the base-free functionalization of aryl esters to form α-functionalized products containing two contiguous tertiary stereogenic centres in excellent yield and stereoselectivity (all ≥99:1 er). Key to the success of this methodology is the multifunctional role of the aryloxide, which operates as a leaving group, Br?nsted base, Br?nsted acid and Lewis base within the catalytic cycle. Comprehensive mechanistic studies, including variable time normalization analysis (VTNA) and isotopologue competition experiments, have been carried out. These studies have identified (i) orders of all reactants; (ii) a turnover-limiting Michael addition step, (iii) product inhibition, (iv) the catalyst resting state and (v) catalyst deactivation through protonation.
One-pot two-step synthesis of 1-(ethoxycarbonyl)indolizines via pyridinium ylides
Allgaeuer, Dominik S.,Mayr, Herbert
supporting information, p. 6379 - 6388 (2013/10/21)
Pyridinium salts Py+-CH2-EWG (EWG = CO2Et, CONEt2, CN, COMe, COPh) reacted with Michael acceptors Ar-CH=C(CO2Et)(Acc) (Acc = CO2Et, COMe, SO2Me, CONH2) at ambient temperature in the presence of base to give [3 + 2]-cycloadducts by stepwise [3 + 2]-cycloaddition of the intermediate pyridinium ylides. Treatment of the crude reaction mixtures with 1 equiv. of chloranil and atmospheric oxygen in the presence of sodium hydroxide gave 1-(ethoxycarbonyl)indolizines by dehydrogenation and elimination of the acceptor group (Acc). A good yield of indolizine was also obtained from Py +-CH2CN and iPr-CH=C(CO2Et)2, which indicates that this method is not restricted to aromatic Michael acceptors. Structurally related isoquinolinium salts react with Michael acceptors analogously to give pyrrolo[2,1-a]isoquinolines.
