138752-03-1Relevant articles and documents
Synthesis of cis,syndiotactic-A-alt-B Copolymers from Enantiomerically Pure Endo-2-Substituted-5,6-Norbornenes
Jang, Eun Sil,John, Jeremy M.,Schrock, Richard R.
, p. 5043 - 5046 (2017)
Cis,syndiotactic A-alt-B copolymers, where A and B are two enantiomerically pure endo-2-substituted-5,6-norbornenes with "opposite" chiralities of the endo-2-substituted-5,6-norbornene skeleton, can be prepared using Mo(N-2,6-Me2C6H3)(CHCMe2Ph)(OHMT)(pyrrolide) (1) as the initiator (OHMT = O-2,6-Mesityl2C6H3). Formation of a high percentage of A-alt-B dyads is proposed to rely on an inversion of chirality at the metal with each propagating step and a kinetically preferred diastereomeric relationship between a given chirality at the metal in propagating species and the chirality of the endo-2-substituted-5,6-norbornene skeleton. We also demonstrate that A-alt-B copolymers can be modified to give new variations which may not be accessible through direct copolymerization.
Silica and alumina modified by Lewis acids as catalysts in Diels-Alder reactions of chiral acrylates
Cativiela,Figueras,Garcia,Mayoral,Pires,Royo
, p. 621 - 624 (1993)
Silica and alumina, modified by treatment with AlClEt2 and TiCl4, are tested as catalysts in the reactions of cyclopentadiene (1) with (-)-methyl acrylate (2a), (R)-O-acryloyl pantolactone (2b) and (S)-O-acryloyl lactate (2c). Silica-modified systems are the most efficient heterogeneous catalysts described to date for this kind of reaction, leading to selectivities similar to those obtained with aluminium homogeneous catalysts. Whereas silica· AlClEt2 is better for the reaction of 2a and 2c, silica· TiCl4 is more suitable for the reaction of 2b.
High viscosity of ionic liquids causes rate retardation of Diels-Alder reactions
Kumar, Anil,Pawar, Sanjay S.
, p. 1633 - 1637 (2012/10/30)
Second order rate constants, k2 have been determined for three bi-molecular Diels-Alder reactions to demonstrate that the high viscosity of ionic liquids can be a detrimental property in carrying out Diels-Alder reactions, if ionic liquids are employed as solvent media. It is possible to enhance the reaction rates of the reaction if a co-solvent is mixed in pure ionic liquid used as a solvent. Science China Press and Springer-Verlag Berlin Heidelberg 2012.
Solvent effects on Diels-Alder reactions. the use of aqueous mixtures of fluorinated alcohols and the study of reactions of acrylonitrile
Cativiela, Carlos,Garcia, Jose I.,Gil,Martinez, Rosa M.,Mayoral, Jose A.,Salvatella, Luis,Urieta, Jose S.,Mainar,Abraham, Michael H.
, p. 653 - 660 (2007/10/03)
Rate, endolexo, regio- and diastereo-facial selectivities of several Diels-Alder reactions were measured in a series of fluorinated alcohol-water mixtures, whose solvophobicity has been determined by means of the solvophobic power (Sp) parameter. Solvophobicity is the main factor influencing the reaction rate, although in some reactions hydrogen bond donating (HBD) ability may also play a role. Both solvophobicity and HBD ability are important to account for changes in endolexo selectivity. HBD ability is the main factor responsible for the changes in regio- and diastereo-facial selectivities, induced by the reaction medium. On the other hand, the kinetic rate constants and endolexo selectivity of the reaction of acrylonitrile with cyclopentadiene, as well as the regioselectivity of the reaction of acrylonitrile with isoprene, have been determined in 23 reaction media. The analysis of the results using empirical solvent parameters show that the reaction rate depends on solvophobic, HBD and dipolarity interactions, whereas endolexo selectivity is influenced by solvophobic and dipolarity interactions, and the regioselectivity only by HBD effects.
