With a nitrogen content of 93.3 %, “perazidomethane” (CN12) is highly explosive but nevertheless isolable. The title compound, which is accessible from commercially available trichloroacetonitrile in one step, undergoes simple dissociation and trapping reactions as well as more‐complex transformations (for example, in the presence of norbornene; see scheme).
Small is beautiful: spectroscopic proof or any other indication for the existence of formyl azide (HC(O)N3) has until now been lacking. Although it liberates dinitrogen much more rapidly than homologous acyl azides, it has been prepared for the first time by four different methods (see scheme).
The simplest acyl azide, HC(O)N3, has been prepared as the neat substance and characterized by IR and Raman spectroscopy and low‐temperature X‐ray crystallography (see solid‐state structure; C white, H gray, N blue, O red). Photolysis of the azide in CO‐doped solid noble‐gas matrices furnished the first experimental proof of the elusive parent acyl isocyanate HC(O)NCO.
Ten different processes (Methods A-J) were tested to prepare tertiary amines bearing bulky alkyl groups. In particular, S1 alkylation of secondary amines with the help of 1-adamantyl triflate (Method D) and reaction of N-chlorodialkylamines with organometallic reagents (Method H), but also attack of the latter reagents at iminium salts, which were generated in situ by N-alkylation of imines (Method J), led to trialkylamines with unprecedented steric congestion. These products showed a restriction of the rotation about the C-N bond. Consequently, equilibration of rotamers was slow on the NMR time scale resulting in distinguishable sets of NMR data at room temperature. Furthermore, tertiary amines with bulky alkyl substituents underwent Hofmann-like elimination when heating in toluene to form an olefin and a secondary amine. Since the tendency to take part in this decay reaction correlated with the degree of steric hindrance around the nitrogen atom, Hofmann elimination at ambient temperature, which made the isolation of the tertiary amine difficult, was observed in special cases.
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