Jc. Boni et al., Nitrosation of amines in nonaqueous solvents. 3. Direct observation of theintermediate in cyclohexane, J ORG CHEM, 64(24), 1999, pp. 8887-8892
The reactions of N-methylaniline (MeAn) with 2,2-dichloroethylnitrite (DCEN
) and 2,2,2-trichloroethylnitrite (TCEN) in cyclohexane, and N-methylmethox
yamine (MMA) with TCEN in the same solvent, all gave the expected N-nitrosa
mines. Spectrophotometric monitoring of the MeAn/DCEN and MMA/TCEN reaction
s showed accumulation of the reaction intermediate. These are the first nit
rosations of amines by alkyl nitrites in which observation of the intermedi
ate has been possible; this is attributed to the low basicity of these amin
es (a) having effectively eliminated the possibility of the intermediate de
composing by base catalysis and (b) having decreased the rate of spontaneou
s decomposition of the intermediate more than the rate of its formation. Be
cause of the scant capacity of cyclohexane to stabilize charge, it is assum
ed that both the formation and decomposition of the intermediate occur via
concerted mechanisms with four-center transition states: formation through
nucleophilic attack by the amine on the nitroso group accompanied by transf
er of the amine proton to this group, decomposition through simultaneous cl
eavage of the N-O bond, and protonation of the alkoxide leaving group.