Rearrangements of the Diels−Alder Cycloadducts Obtained from Acetylenic Sulfones and 1,3-Diphenylisobenzofuran Thomas G. Back Masood Parvez Huimin Zhai 10.1021/jo060598e.s006 https://acs.figshare.com/articles/dataset/Rearrangements_of_the_Diels_Alder_Cycloadducts_Obtained_from_Acetylenic_Sulfones_and_1_3_Diphenylisobenzofuran/3072022 1,3-Diphenylisobenzofuran afforded Diels−Alder cycloadducts <b>4a</b>,<b>b</b> with <i>n</i>-butyl- and phenyl-substituted acetylenic sulfones <b>3a</b>,<b>b</b>, respectively. The products underwent various types of rearrangements under pyrolytic, acid-catalyzed, and photochemical conditions. In the presence of acid, or upon heating in xylenes, they afforded the ketones <b>5a</b>,<b>b</b>. In addition, the dehydration product <b>7a</b> was produced from the pyrolysis of <b>4a</b>, and the unexpected transposed ketone <b>6b</b> was generated under acid-catalyzed or pyrolytic conditions from <b>4b</b> via a postulated epoxide intermediate. The photolysis of <b>4a </b>afforded ketone <b>5a</b> as the sole isolated product, whereas <b>5b</b> afforded oxepin <b>8b</b> and indenyl phenyl ketone <b>9b</b>. The formation of the latter two products can be rationalized by a series of pericyclic reactions. These include an intramolecular [2+2] cycloaddition, followed by a 1,3-dipolar cycloreversion, for the transformation of <b>4b</b> to <b>8b</b> and a series of electrocyclic and [1,3]sigmatropic reactions to convert <b>8b</b> into <b>9b</b>. 2006-07-07 00:00:00 series dehydration product 7 Diel 4 b 8 b ketone 6 b pyrolytic oxepin 8 b indenyl phenyl ketone 9 b