Approach to Loschmidt's tetracyclic benzene isomer and related tetra- and tricyclic isomers by intramolecular carbene additions

作者：Roth Heinz D^*; Sauers Ronald R

来源：Journal of Physical Organic Chemistry, 2015, 28(2): 88-96.

DOI：10.1002/poc.3391

• foiled reaction carbenes
• intramolecular carbene addition
• strained-ring carbenes

Potential carbene precursors have been considered for three tetracyclic benzene isomers: carbene 13(..) for tetracyclo[3.1.0.0(1,3).0(3,5)]hexane, 11; carbene 19(..) for tetracyclo[3.1.0.0(1,4).0(2,3)]hexane, 10, considered by Loschmidt as a structure for benzene; and carbene 20(..) for Ladenburg's prismane, 4. The bicyclic (CH)(6) isomer, 20(..), avoids intramolecular cycloaddition; it is converted instead to Dewar benzene, 2; the system 13(..) - 11(..) is a foiled carbene system; finally, we were unable to characterize the putative precursor, 19(..), for Loschmidt's hydrocarbon; an attempt to generate it by adding an electron to the corresponding carbene cation, 19(.+), resulted in conversion to anti-10. The trajectory of this conversion indicates that 19(..) lies at or below the inflection point of the trajectory connecting a putative transition state with anti-10. The free energies of all six species lie in the range 120-165kcal/mol, well above any species that may be involved in the topomerization of benzene.

• 出版日期2015-2
• 单位rutgers