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TS-Torquoselectivity from Global Conformational Profile
preprintsubmitted on 06.01.2021, 07:53 and posted on 07.01.2021, 05:12 by Veejendra Yadav, Arpita Yadav, Maddali L N Rao
From the global conformational profile and differential activation free energies of conrotatory outward and inward ring openings of all the conformers, it is shown that (a) 3-OMe-cyclobutene must open exclusively outward and (b) conformers exist for 3-CHO- and 3-COMe-cyclobutenes that will open outwards as well. All the conformers of 3-OMe-, 3-CHO- and 3-COMe-cyclobutenes are, respectively, within 5.6, 3.2 and 4.0 kcal/mol and, hence, abundantly available under the reaction conditions. 3-OMe-cyclobutene is experimentally known to open exclusively outward. 3-CHO-cyclobutene opens > 98% inward and < 2% outward. In contrast with 3-CHO-cyclobutene, 3-COMe-cyclobutene furnishes a 3:2 mixture of the outward and inward products, respectively.