16429-05-3Relevant academic research and scientific papers
Stereoselective alkene isomerization over one position
Larsen, Casey R.,Grotjahn, Douglas B.
, p. 10357 - 10360 (2012/08/08)
Although controlling both the position of the double bond and E:Z selectivity in alkene isomerization is difficult, 1 is a very efficient catalyst for selective mono-isomerization of a variety of multifunctional alkenes to afford >99.5% E-products. Many reactions are complete within 10 min at room temperature. Even sensitive enols and enamides susceptible to further reaction can be generated. Catalyst loadings in the 0.01-0.1 mol% range can be employed. E-to-Z isomerization of the product from diallyl ether was only -6 times as fast as its formation, showing the extremely high kinetic selectivity of 1.
Highly active and selective platinum(II)-catalyzed isomerization of allylbenzenes: Efficient access to (E)-anethole and other fragrances via unusual agostic intermediates
Scarso, Alessandro,Colladon, Marco,Sgarbossa, Paolo,Santo, Claudio,Michelin, Rino A.,Strukul, Giorgio
experimental part, p. 1487 - 1497 (2010/05/15)
Terminal alkene isomerization reactions can be efficiently catalyzed by PtII complexes bearing a chelating diphosphine and an alkyl or, better, aryl moiety under mild experimental conditions. In particular diphosphines, such as dppb, characterized by a large bite angle in conjunction with a pentafiuorophenyl residue coordinated to Pt enable quantitative conversion of the reagent into internal, alkenes within few hours at 50 °C in CHCl3 as solvent. E/Z selectivity can be as high as 98:2 for allylbenzene, and the catalytic system can be fruitfully applied to the preparation of E fragrances derived by isomerization of substituted, allylbenzene derivatives. The selectivity increases during the progress of the reaction because of a subsequent catalytic step where the Z alkene coordinates to the Pt and is converted into the E isomer. NMR investigation on the catalyst showed formation of agostic Pt...H intermediate species derived by insertion of the substrate into the Pt-aryl bond followed by β-hydride elimination. Formation of such agostic species is promoted by the steric hindrance imparted by the diphosphine characterized by a large bite angle. Kinetic studies and DFT calculations on the possible agostic intermediates shed light on their structure and enable the formulation of a possible catalytic mechanism.
