Nitrogen, electron structure leaving group

Propylein, the other alkaloid of this group, appears to be the sole alkaloid of the beetle Propylaea quatuordecimpmctata Propylein is an amorphous, unstable, laevorotatory base of molecular formula C13H21N which affords precoccinellin on hydrogenation. Since the alkaloid contains one olefinic proton that is in an enamine system (n.m.r., i.r.), three dehydroprecoccinellin structures are possible for propyleia Two of these can be excluded, since propylein exhibits only end absorption in the u.v. It thus appears that in propylein the 7r-electron system of the double bond is so oriented that it cannot interact with the unshared electrons on the nitrogen atom. This leaves only one possible structure (32) for propylein [cf. conformation (33)]. ... 

From what has been written so far it follows that the initiation of nitramines by impact should be dominated by the key role of the aza-atoms carrying the primarily leaving nitro groups [6,7]. The dominant factor in the initiation by shock, electric spark, and in low-temperature thermolysis should be the electronic structure and surroimdings of the primarily leaving nitro group [6,7]. For nitramine molecules, whose nitrogen atoms are not isochronous, the said fact is documented in Scheme 6. 

Zollinger and coworkers (Nakazumi et al., 1983) therefore supposed that the diazonium ion and the crown ether are in a rapid equilibrium with two complexes as in Scheme 11-2. One of these is the charge-transfer complex (CT), whose stability is based on the interaction between the acceptor (ArNj) and donor components (Crown). The acceptor center of the diazonium ion is either the (3-nitrogen atom or the combined 7r-electron system of the aryl part and the diazonio group, while the donor centers are one or more of the ether oxygen atoms. The other partner in the equilibrium is the insertion complex (IC), as shown in structure 11.5. Scheme 11-2 is intended to leave the question open as to whether the CT and IC complexes are formed competitively or consecutively from the components. ... 

---