Abstract
The reaction of 1,4,7-triazacyclononane with
tris(3-chloropropyl)amine affords the inside monoprotonated form
of the tricyclic amine 1,4,8,12-tetraazatricyclo [6.6.3.2 sup
4,12]nonadecane (3), which was isolated as the bromide salt,
[H[(2.3)sup 3]adz]Br (yield 38%). The crystal structure of
[H[(2.3)sup 3]adz]Br x 4H sub 2 O has been solved by X-ray
diffraction at T = 120 K. In the i sup +,i,i,i-H[(2.3) sup 3] adz
sup + cation (3a) the acidic hydrogen atom and the lone pairs of
the nitrogen atoms are oriented towards the inside of the cavity.
The acidic hydrogen atom is attached to the apical nitrogen atom
and both are positioned on a three-fold axis. The distances
between the nitrogen atoms are in the range of 2.73(2)-2.99(1) Å.
The inside coordinated proton in H[(2.3)sup 3]adz sup + cation
(3a) is unusually inert to reaction with base (k sub diss < 4 x 10 sup -9 s sup-1 at 25 degrees C in 0.01 M NaOD). From sup 1
H and sup 13C NMR it is concluded that in slightly acidic (pH
> 2) and in basic aqueous solutions the dominant form of
the cage has all four lone pairs pointing into the cavity. In
concentrated strong acid protonation occurs and is believed to
involve inversion at one or several of the bridgehead nitrogen
atoms. In concentrated boiling hydrochloric acid the cage
undergoes a slow cleavage of one trimethylene bridge to give the
bowl amine [(2.3) sup 2. 2 sup 1]adz (7),
1,5,9,12-tetraazabicyclo[7.5.2]hexadecane, which was isolated as
the triprotonated bromide dichloride salt, [H sub 3[(2.3) sup 2. 2
sup 1]adz]BrCl sub 2 x H sub 2 O (yield 40%).
| Original language | English |
|---|---|
| Journal | J. Chem. Soc., Perkin Trans. |
| Volume | 2 |
| Pages (from-to) | 2701-2706 |
| Publication status | Published - 1999 |