Trimethylenemethane diyls

The generation of trimethylenemethane diyls [26] has been shown to effect DNA cleavage. Attachment of this group to a DNA binding molecule (Fig. 7) made the intramolecular hydrogen atom abstraction (DNA-drug being considered as one molecule) more efficient than the competitive dimerization of diyls. 

Fig. 7 Photogeneration of distamycin-bound trimethylenemethane diyls generated from a diazene precursor... 

AUan AK, Law Carroll G, Little RD. The versatile trimethylenemethane diyl. Diyl trapping reactions. Retrospective and new modes of reactivity. Eur J Org Chem. 1998 1-12. 

Reaction of linear compounds containing a ketone and diene functional groups with TMSC(Li)N2 produces alkylidene carbenes that undergo intramolecular cyclopropanation followed by formation of trimethylenemethane diyls and then [3 + 2]cyclo-addition, giving linearly fused triquinanes (eq 31). ... 

Interactions polarize bonds. Trimethylenemethane (TMM) and 2-buten-l,4-diyl (BD) dianions (Scheme 6a, b) are chosen as models for hnear and cross-conjngated dianions. The bond polarization (Scheme 7) is shown to contain cyclic orbital interaction (Scheme 6c) even in non-cyclic conjugation [15]. The orbital phase continnity-discon-tinnity properties (Scheme 6d, e) control the relative thermodynamic stabihties. 

There is a degree in the continuity and discontinuity of the orbital phase [20]. 2-Oxopropane-l,3-diyl (Scheme 10) is a hetero analog of trimethylenemethane (TMM) where the orbital phase is continuous in the triplet diradical (Sect. 2.1.5) and discontinuous in the singlet diradical (Sect. 2.1.6). The n and orbitals of carbonyl bonds are lower in energy than those of C=C bonds. The lowering strengthens the interaction of the radical orbitals (a, b) with and weakens that... 

Experimental evidence for the six electron systems has been described in Sect. 2.1.4. Skancke reproduced the relative stabihty of the cross conjugated systems relative to the linear isomers by calculating the trimethylenemethane and buta-l,4-diyl dianions [27] and their dilithio salts [28]. For the four electron systems butadiene is more stable than trimethylenemethane. Experimental examination of the relative stabihties of two electron systems using the trimethylenemethane and buta-14-diyl dications needs to overcome the intrinsic instabihties of dications dissatisfying the octet rule. 

Both the thermally and the photochemically initiated extrusion of nitrogen from bicyclic diazene (1) leads to the formation of a 1,3-diradical (diyl) which is structurally related to trimethylenemethane. As shown in the cascade mechanism illustrated, two forms of the diyl can be intercepted by alkenes bearing electron-withdrawing groups (diylophiles), viz. the open form of the singlet diyl and the triplet diyl which is formed via intersystem crossing from the singlet (Scheme 1). ... 

We recently reported tandem reaction strategies for obtaining triquinanes from linear substrates through trimethylenemethane (TMM) diyl [2+3]... 

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