PET-oxidative reactions of siloxy-cyclopropanes

Rinderhagen H, Mattay J. PET-oxidative reactions of siloxy-cyclopropanes. JOURNAL OF INFORMATION RECORDING. 1998;24(3-4):261-264.The oxidative reaction of 1-trimethysiloxy-cyclopropanes has been investigated under PET conditions. The mechanism could be partially elucidated concerning the first reaction steps. The equilibrium of the mutual rearranging exo- and endo- radicals is determined by ring strain and radical-stability

Synthetic applications in radical/radical cationic cascade reactions

Rinderhagen H, Mattay J. Synthetic applications in radical/radical cationic cascade reactions. CHEMISTRY-A EUROPEAN JOURNAL. 2004;10(4):851-874.Oxidative photoinduced electron transfer (PET) reactions have been performed with various cyclic cyclopropyl(vinyl) silyl ethers bearing an olefinic or acetylenic side chain. The reactions result in bi- to tetracyclic ring systems via a fragmentation-radical/ radical cationic addition reaction pathway with well defined ring juncture. The mode of cyclisation (endo/exo) can be partially controlled by addition of nucleophiles due to the suppression of radical cationic reaction pathways. Quantum chemical calculation of the cyclisation transition states underline the experimentally found selectivities. Additional mechanistic studies concerning the saturation step reveal that the final radical is saturated mostly by the solvent and traces of water in the solvent

PET-oxidative generation of beta-ketoradicals. Optimisation of intermolecular radical addition reactions

Rinderhagen H, Grota J, Mattay J. PET-oxidative generation of beta-ketoradicals. Optimisation of intermolecular radical addition reactions. JOURNAL OF INFORMATION RECORDING. 2000;25(1-2):229-233.Siloxy cyclopropanes are easily oxidizable by photoinduced electron transfer (PET) reagents. The fragmentation of the resulting radical cations leads to beta -ketoradicals. The usability of these radicals in intermolecular addition reactions is limited by polymerisation or reduction. This disadvantage can be partially circumvented by studying the influence of the concentration of the reaction partners

Facile ring opening of siloxy cyclopropanes by photoinduced electron transfer. A new way to beta-keto radicals

Rinderhagen H, Waske PA, Mattay J. Facile ring opening of siloxy cyclopropanes by photoinduced electron transfer. A new way to beta-keto radicals. TETRAHEDRON. 2006;62(27):6589-6593.Siloxy cyclopropanes undergo ring opening and fragmentation of formal silyl cations under formation of beta-keto radicals. These reactive intermediates can be used in inter- and intramolecular addition reactions leading to complex ring systems if more than one unsaturated side chain is present in the starting material. Beside some synthetic examples mainly the mechanism will be discussed focusing on the structure of the primarily formed radical cations, the regioselectivity of cyclopropane cleavage (endo vs exo ring opening). leaving of the silyl group, and termination by H-transfer. (c) 2006 Elsevier Ltd. All rights reserved