Spectroscopic and calorimetric studies on the mechanism of methylenecyclopropane rearrangements triggered by photoinduced electron transfer

Journal of the American Chemical Society
Hiroshi IkedaTsutomu Miyashi

Abstract

2-(dideuteriomethylene)-1,1-bis(4-methoxyphenyl)cyclopropane (d(2)-1) undergoes degenerate rearrangement in both singlet- and triplet-sensitized electron-transfer photoreactions. Nanosecond time-resolved absorption spectroscopy on laser flash photolysis of the unlabeled 1 with 9,10-dicyanoanthracene, 1,2,4,5-tetracyanobenzene, or N-methylquinolinium tetrafluoroborate as an electron-accepting photosensitizer gives rise to two transients with lambda(max) at 500 and 350 nm assigned to the dianisyl-substituted largely twisted trimethylenemethane cation radical (6.+) and the corresponding diradical (6..), respectively. These intermediates are also detected, respectively, by steady state and nanosecond time-resolved EPR with chloranil or anthraquinone as a sensitizer. The degenerate rearrangement of d(2)-1 thus proceeds via these two different types of intermediates in a cation radical cleavage-diradical cyclization mechanism. Energetics based on nanosecond time-resolved photoacoustic calorimetry support this mechanism. A comparison of the reactivities and the spectroscopic results of 1, 1,1-bis(4-methoxyphenyl)-2-methylenespiro[2.2]pentane (2), and 1-cyclopropylidene-2,2-bis(4-methoxyphenyl)cyclopropane (3) suggest that the reversib...Continue Reading

Citations

Apr 14, 2016·Chemical Reviews·Davide RavelliMaurizio Fagnoni
Apr 26, 2016·Chemical Reviews·Kazimer L SkubiTehshik P Yoon
Sep 19, 2007·Angewandte Chemie·Claire MadelaineOlivier Buriez
Jun 15, 2005·Chemistry : a European Journal·J Chris SlootwegKoop Lammertsma
Sep 24, 2013·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Heinz D Roth, Ronald S Sauers
Jan 24, 2014·Beilstein Journal of Organic Chemistry·Alexander O Terent'evValery M Dembitsky
Feb 8, 2005·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Virginie LatourSylvie Lacombe
Sep 20, 2011·Journal of the American Chemical Society·Yusuke InagakiAkira Sekiguchi
Oct 13, 2005·Journal of the American Chemical Society·Hiroshi IkedaTsutomu Miyashi

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