Chameleon catches in combinatorial chemistry: Tebbe olefination of polymer supported esters and the synthesis of amines, cyclohexanones, enones, methyl ketones and thiazoles
作者:Christopher P. Ball、Anthony G. M. Barrett、Delphine Compère、Cyrille Kuhn、Richard S. Roberts、Marie L. Smith、Olivier Venier、Alain Commerçon
DOI:10.1039/a805874a
日期:——
Tebbe olefination of supported esters R1CO2CH2–polymer gave the corresponding vinyl ethers R1C(CH2)OCH2–polymer which were released, under acidic conditions, to produce methyl ketones R1COMe; by reductive amination, to produce amines R1CH(Me)NHR2; by bromination and reaction of R1CBr(CH2Br)OCH2-polymer with thioureas to produce thiazoles; or, for supported dienyl ethers derived from α,β-unsaturated esters, by Diels–Alder reaction and acid mediated cleavage to produce cyclohexanone derivatives.
A Convenient Route to (<i>E</i>)-α,β-Unsaturated Methyl Ketones
作者:M. Bellassoued、J. Aatar、M. Bouzid、M. Damak
DOI:10.1080/10426500903348039
日期:2010.8.25
Aldehydes are converted into (E)-α,β-unsaturated methyl ketones in good yield and with a high E stereoselectivity using α,α-bis(trimethylsilyl) N-tert-butyl acetimine 3. The reaction was mediated by a catalytic amount of tetrabutylammonium fluoride (TBAF) under mild conditions. The disilylated reagent 3 is easily generated from N-tert-butylacetimine, lithium diisopropylamide (LDA), and chlorotrimethylsilane
In situ 1H-PHIP-NMR studies of the stereoselective hydrogenation of alkynes to ( E)-alkenes catalyzed by a homogeneous [Cp*Ru]+ catalyst
作者:Dana Schleyer、Heiko G. Niessen、Joachim Bargon
DOI:10.1039/b007201j
日期:——
The hydrogenation of internal alkynes using a [Cp*Ru(alkene)]+ complex leads to the formation of (E)-alkenes. This ruthenium complex represents one of the few homogeneous catalysts that trans-hydrogenate internal alkynes directly and stereoselectively. We have studied its stereoselectivity by in situ PHIP-NMR spectroscopy (PHIP = para-hydrogen
induced polarization). With this method the initially formed products can be identified and characterized even at very low concentrations and low conversions. Furthermore, their subsequent fate can be evaluated with high sensitivity and with time resolution. Different alkyne substrates were used to demonstrate the universal applicability of this catalyst. The catalyst is not active in combination with terminal alkynes, however, possibly due to the formation of a rather stable vinylidene complex. A mechanism
proceeding ia a binuclear complex is proposed to explain the formation of the (E)-alkenes.
Dynamic π-Bonding of Imidazolyl Substituent in a Formally 16-Electron Cp*Ru(κ<sup>2</sup>-<i>P</i>,<i>N</i>)<sup>+</sup> Catalyst Allows Dramatic Rate Increases in (<i>E</i>)-Selective Monoisomerization of Alkenes
作者:Erik R. Paulson、Curtis E. Moore、Arnold L. Rheingold、David P. Pullman、Ryan W. Sindewald、Andrew L. Cooksy、Douglas B. Grotjahn
DOI:10.1021/acscatal.8b04345
日期:2019.8.2
in κ2-P,N coordination. For the first time, we show direct experimental evidence that the PN ligand has accepted a proton from the substrate by characterizing the intermediate Cp*Ru[η3-allyl][κ1-P)P–N+H], which highlights the essential role of the bifunctional ligand in promoting rapid and selective alkene isomerizations. Moreover, kinetic studies and computations reveal the role of alkene binding in
Catalyst versus Substrate Control of Forming (<i>E</i>)-2-Alkenes from 1-Alkenes Using Bifunctional Ruthenium Catalysts
作者:Erik R. Paulson、Esteban Delgado、Andrew L. Cooksy、Douglas B. Grotjahn
DOI:10.1021/acs.oprd.8b00315
日期:2018.12.21
Here we examine in detail two catalysts for their ability to selectively convert 1-alkenes to (E)-2-alkenes while limiting overisomerization to 3- or 4-alkenes. Catalysts 1 and 3 are composed of the cations CpRu(κ2-PN)(CH3CN)+ and Cp*Ru(κ2-PN)+, respectively (where PN is a bifunctional phosphine ligand), and the anion PF6–. Kinetic modeling of the reactions of six substrates with 1 and 3 generated