87482-94-8Relevant academic research and scientific papers
Zn-Catalyzed Enantio- and Diastereoselective Formal [4 + 2] Cycloaddition Involving Two Electron-Deficient Partners: Asymmetric Synthesis of Piperidines from 1-Azadienes and Nitro-Alkenes
Chu, John C. K.,Dalton, Derek M.,Rovis, Tomislav
supporting information, p. 4445 - 4452 (2015/04/14)
We report a catalytic asymmetric synthesis of piperidines through [4 + 2] cycloaddition of 1-azadienes and nitro-alkenes. The reaction uses earth abundant Zn as catalyst and is highly diastereo- and regioselective. A novel BOPA ligand (F-BOPA) confers high reactivity and enantioselectivity in the process. The presence of ortho substitution on the arenes adjacent to the bis(oxazolines) was found to be particularly impactful, due to limiting the undesired coordination of 1-azadiene to the Lewis acid and thus allowing the reaction to be carried out at lower temperature. A series of secondary kinetic isotope effect studies using a range of ligands implicates a stepwise mechanism for the transformation, involving an initial Michael-type addition of the imine to the nitro-alkene followed by a cyclization event. The stepwise mechanism obviates the electronic requirement inherent to a concerted mechanism, explaining the successful cycloaddition between two electron-deficient partners. (Chemical Equation Presented).
Synthetic and quantum mechanical studies into the N- heterocyclic carbene catalyzed (4 + 2) cycloaddition
Ryan, Sarah J.,Stasch, Andreas,Paddon-Row, Michael N.,Lupton, David W.
experimental part, p. 1113 - 1124 (2012/03/10)
The N-heterocyclic carbene catalyzed (4 + 2) cycloaddition between α,β-unsaturated acid fluorides and TMS dienol ethers provides cyclohexene fused β-lactone intermediates stable below -20 °C. These can be intercepted reductively or with organolithium reag
Base-free mizoroki-heck reaction catalyzed by rhodium complexes
Martinez, Remi,Voica, Florina,Genet, Jean-Pierre,Darses, Sylvain
, p. 3213 - 3216 (2008/02/11)
A base-free rhodium-catalyzed Mizoroki-Heck (M-H) reaction using potassium aryltrifluoroborates as the arylating agent of alkenes and acetone as a green "oxidant" is described. Thanks to the ready availability of organoboranes, this reaction should consti
Bromide Ion Promoted β-Elimination in α-Bromo Ester Substrates. Evidence for an Intermediate in the E2C Reaction
Kwart, Harold,Gaffney, Anne
, p. 4502 - 4508 (2007/10/02)
The TDKIE criteria of transition state geometry in H-transfer reactions have been applied in the title reactions; a bent transition state consistent with the geometry of the E2C reaction has been verified by the results of intramolecular and intermolecular competition modes of determining kH/kD as a function of temperature.The extraordinary magnitude measured for the α secondary deuterium isotope effect in the E2C mechanism is reconciled with a very loose transition state and an acute angle of H-abstraction in the course of rearward approach to Cα by the promoter base.The virtual identity of the inter- and intramolecular isotope effects can be correlated by the assumption of a reaction intermediate of trigonal-bipyramid structure surrounding Cα and in which the abstractable H and D atoms are equally available to the action of the promoter base.The properties of this intermediate (4), by way of contrast with the transition state of an SN2 process, are discussed in detail.
