Trimethylenemethane radicals

Intra-complex TMS+ abstraction by F yields the trimethylenemethane radical anion 33. Similarly, a number of other (mostly aromatic) distonic radical anions have been generated. Using the same approach, several other highly unsaturated distonic negative ions, such as the benzyne radical anions, were also studied164. 

It is obvious that the isobutene unit provides a good starting point for the generation of trimethylenemethane radical anions. However, even isobutane units can be used to produce these more highly unsaturated species. In a preliminary work aimed at two-and three-fold deprotonation processes in solution, Kuck, de Meijere and coworkers165 have subjected triquinacene (41) and the tribenzotriquinacenes 44 to NCI conditions with... 

CH4/O2 and CF4 as the reactant gases and observed the formation of [M — 4 H] ions in the Cl plasma (Scheme 13)166. Thus, repeated deprotonation and electron transfer processes appear to offer an efficient access to more highly unsaturated and/or ring condensed trimethylenemethane radical anions. The [M — 4 H]- ion is considered identical to the molecular radical anion (42) of acepentalene (43), which was generated as a short-lived species from the former by neutralization-reionization mass spectrometry167. Efforts to apply Squires methodology to triquinacene 41 and the tribenzotriquinacenes 44 have been made168. 

The second example of triplet BET in radical ion pairs involves the (ring-opened, distonic) trimethylenemethane radical cation (24 ) generated in the... 

In the second group of radical cations to be discussed here, spin and charge are stabilized in two separate fragments of the molecule. In early examples of this family the charge was stabilized by diaryl or methoxy substitution. We mention the ring-opened trimethylenemethane radical cations (152), the various di-... 

The photooxygenation of 2,2-diaryImethylenecyclopropanes proceeds via trimethylenemethane radical cation intermediates, giving 1,2-dioxolanes [160,161]. When 1,1,2,2-tetracyanoethene (TONE) is used as an electron acceptor, the (3 + 2) cycloaddition between methylenecyclopropanes and... 

Scheme 13. Reactions of a substituted trimethylenemethane radical cation.

Furthermore, we deal with a stfuctural distortion of the trimethylenemethane radical cation (TMM+) [63], The neutfal TMM has a high symmetry of and is in a triplet state with a doubly degenerate c" HOMO in the ground electronic state [64], The Z)3h structure of TMM is expected to be distorted to a Civ structure with a lower symmetry in TMM+ due to the J-T effect, so as to split the original degenerate e" orbitals into ai and b orbitals. 

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