Pericyclic reactions hydrophobic effect

Apart from the thoroughly studied aqueous Diels-Alder reaction, a limited number of other transformations have been reported to benefit considerably from the use of water. These include the aldol condensation , the benzoin condensation , the Baylis-Hillman reaction (tertiary-amine catalysed coupling of aldehydes with acrylic acid derivatives) and pericyclic reactions like the 1,3-dipolar cycloaddition and the Qaisen rearrangement (see below). These reactions have one thing in common a negative volume of activation. This observation has tempted many authors to propose hydrophobic effects as primary cause of ftie observed rate enhancements. [Pg.27]

Reviews describe several organic reactions that are successfully carried out in aqueous media (Li, 1993 Li, 2000). In some cases, notably in the Diels-Alder reaction and in other pericyclic reactions, the hydrophobic effect accelerates the reaction and... [Pg.160]

Hydrophobic Effects in Pericyclic Reactions 923 Pericyclic Reactions of Radical Cations 925... [Pg.1127]