83833-01-6Relevant academic research and scientific papers
Triazine-Based Cationic Leaving Group: Synergistic Driving Forces for Rapid Formation of Carbocation Species
Fujita, Hikaru,Kakuyama, Satoshi,Fukuyoshi, Shuichi,Hayakawa, Naoko,Oda, Akifumi,Kunishima, Munetaka
, p. 4568 - 4580 (2018/04/26)
A new triazine-based cationic leaving group has been developed for the acid-catalyzed alkylation of O- and C-nucleophiles. There are two synergistic driving forces, namely, stable C=O bond formation and charge-charge repulsive effects, involved in the rapid generation of the carbocation species in the presence of trifluoromethanesulfonic acid (～200 mol %). Considerable rate acceleration of benzylation, allylation, and p-nitrobenzylation was observed as compared to the reactions with less than 100 mol % of the acid catalyst. The triazine-based leaving group showed superior p-nitrobenzylation yield and stability in comparison to common leaving groups, trichloroacetimidate and bromide. A plausible reaction mechanism (the cationic leaving group pathway) was proposed on the basis of mechanistic and kinetic studies, NMR experiments, and calculations.
Rearrangements of Oxocyclopropanecarboxylate Esters to Vinyl Ethers. Disparate Behavior of Transition-Metal Catalysts
Doyle, Michael P.,Leusen, Daan van
, p. 5326 - 5339 (2007/10/02)
Diverse transition-metal compounds catalyze the conversion of 2-alkoxycyclopropanecarboxylate esters to derivative vinyl ethers in high yield under mild conditions.With 2, PtCl2*2PhCN, or 2, structural rearrangement occurs with concurrent epimerization of the reactant cyclopropane compound, and identical isomeric mixtures of vinyl ethers are formed from either of the two stereoisomeric cyclopropane reactants.Rhodium(II) acetate catalyzed reactions occur at higher temperatures than those required with 2, epimerization of the (Z)-cyclopropane isomer, but not the E isomer, is observed, and individual stereoisomeric cyclopropane reactants produce different isomeric mixtures of vinyl ether products.The characteristics of copper bronze and copper(I) chloride catalyzed reactions are generally similar to those of Rh2(OAc)4, except with ethyl 2-methoxy-2-vinylcyclopropanecarboxylate, which undergoes rearrangement to the isomeric ethyl 3-methoxycyclopentenecarboxylates in the presence of these copper catalysts.Participation by the carbethoxy group in rhodium(I)-, platinum (II)-, and ruthenium(II)-catalyzed reactions is indicated in results from comparative reactions with nitrile and sulfone derivatives, and the mechanistic involvement of a six-membered ring metallocycle is suggested.In rhodium(II)- and copper-catalyzed reactions, metallocyclobutane intermediates are proposed to account for their contrasting results.Catalytic rearrangement of (allyloxy)cyclopropanecarboxylate esters affords 3-allyl-4-oxoalkanoate esters in good yield by a synthetic coupling of the oxocyclopropane-vinyl ether and Claisen rearrangement transformations.
