PMID: 11929249Apr 4, 2002Paper

Unusual temperature dependence in the cis/trans-oxetane formation discloses competitive syn versus anti attack for the Paternò-Büchi reaction of triplet-excited ketones with cis- and trans-cylooctenes. Conformational control of diastereoselectivity in the cyclization and cleavage of preoxetane diradicals

Journal of the American Chemical Society
Waldemar Adam, Veit R Stegmann

Abstract

Toluene-d(8) solutions of cis- and trans-cyclooctene (cis- and trans-1a) as well as (Z)- and (E)-1-methylcyclooctene (cis- and trans-1b) have been irradiated at temperatures between -95 and +110 degrees C in the presence of benzophenone (BP) to afford mixtures of the cis- and trans-configured oxetanes 2a,b and the regioisomeric 2b'. Correspondingly, benzoquinone (BQ) gave with cis- and trans-1a the cycloadducts cis- and trans-3a. The cis/trans diastereomeric ratios of the [2 + 2]-cycloadducts 2 and 3 display a strong temperature dependence; with cis- and trans-1a or cis-1b as starting materials, the diastereoselectivity of the oxetane formation is high at low temperature, under preservation of the initial cyclooctene configuration. With increasing temperature, the cis diastereoselectivity decreases continuously for the cis-cyclooctenes; in the case of the cis-1a, the diastereoselectivity is even switched to trans (cis/trans ca. 20:80) at very high temperatures. For the strained trans-1a, the trans-oxetanes are strongly preferred over the entire temperature range, with only minor leakage (up to 10%) to the cis-oxetanes at very high temperatures. Oxetane formation is accompanied by nonthermal trans-to-cis isomerization of the cyc...Continue Reading

Citations

Mar 31, 2011·Beilstein Journal of Organic Chemistry·Feng-Feng KongQin-Hua Song
Sep 18, 2013·Molecules : a Journal of Synthetic Chemistry and Natural Product Chemistry·Maurizio D'Auria, Rocco Racioppi
Mar 9, 2011·IEEE Transactions on Pattern Analysis and Machine Intelligence·Georgios PassalisIoannis A Kakadiaris
May 27, 2006·IEEE Transactions on Pattern Analysis and Machine Intelligence·Toni Tamminen, Jouko Lampinen
Feb 4, 2005·IEEE Transactions on Pattern Analysis and Machine Intelligence·Pedro F Felzenszwalb
Apr 19, 2008·Chemistry & Biology·Michael C PirrungBrad M Binder
Jul 22, 2008·Chemistry : a European Journal·Olaf Muehling, Pablo Wessig
Oct 30, 2008·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Feng-Feng KongQin-Hua Song
Sep 21, 2005·Angewandte Chemie·Pablo Wessig, Olaf Mühling
Jul 6, 2019·Photochemical & Photobiological Sciences : Official Journal of the European Photochemistry Association and the European Society for Photobiology·Maurizio D'Auria

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