Aminomethyl Transfer (Mannich) Reactions Between an O-Triethylsilylated Hemiaminal and Anilines, RnC6H5?nNH2 Leading to New Diamines, Triamines, Imines, or 1,3,5-Triazines Dependent upon Substituent R

Article abstract of DOI:10.1002/chem.201901877

The reactions of the Mannich reagent Et₃SiOCH₂NMe₂ (1) with a variety of anilines (mono-substituted RC₆H₄NH₂, R=H, 4-CN, 4-NO₂, 4-Ph, 4-Me, 4-MeO, 4-Me₂N; di-substituted R₂C₆H₃NH₂, R₂=3,5-(CH₃)₂, 3,5-(CF₃)₂; tri-substituted R₃C₆H₂NH₂, R₃=3,5-Me₂-4-Br and a “super bulky” aniline (Ar*NH₂) [Ar=2,6-bis(diphenylmethyl)-4-tert-butylphenyl]) led to the formation of a range of products dependent upon the substituent. With electron-withdrawing substituents, previously unknown diamines, RC₆H₄NH(CH₂NMe₂) [R=CN (2 a), NO₂ (2 b)] and R₂C₆H₃NH(CH₂NMe₂) [R₂=3,5-(CF₃)₂ (2 c)] were formed. Further reaction of 2 a, b, c with 1 yielded the corresponding triamines RC₆H₄N(CH₂NMe₂)₂ (R=CN (3 a), NO₂ (3 b) and R₂C₆H₃N(CH₂NMe₂)₂, R₂=3,5-(CF₃)₂ (3 c). The new polyamines were characterized by NMR spectroscopy, and for 2 a, 2 c_, and 3 c, by single crystal XRD. In the case of electron-donating groups, R=4-OMe, 4-NMe₂, 4-Me, 3,5-Me₂, 3,5-Me₂-4-Br, and for R=4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R=4-MeO (5 a), 4-Me₂N (5 b), 4-Me (5 c), 3,5-Me₂ (5 d), 3,5-Me₂-4-Br (5 e), 4-Ph (5 f), 4-Cl (5 g). The “super bulky” aniline rapidly produced a single product, namely the corresponding imine Ar*N=CH₂ (4) which was also characterized by single crystal XRD. Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are tempted to denote the reactions of 1 as examples of “Silick” chemistry.

Full text of DOI:10.1002/chem.201901877

A Journal of
Accepted Article
Title: Aminomethyl transfer (Mannich) reactions between an O-
triethylsilylated hemiaminal and anilines, RnC6H5-nNH2 leading
to new diamines, triamines, imines or 1,3,5-triazines dependent
upon substituent R
Authors: Anwar Jacintomoreno, Hemant K. Sharma, Alejandro Metta-
Magaña, and Keith H. Pannell
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10.1002/chem.201901877
Chemistry - A European Journal
Aminomethyl transfer (Mannich) reactions between an O-triethylsilylated
hemiaminal and anilines, RnC6H5-nNH2 leading to new diamines, triamines,
imines, or 1,3,5-triazines dependent upon substituent R
Anwar Jacintomoreno, Hemant K. Sharma, Alejandro Metta-Magaña, Keith H.
Pannell
Department of Chemistry, University of Texas at El Paso, El Paso, TX. 79968-0513,
USA
Abstract The reactions of the Mannich reagent Et3SiOCH2NMe2 (1) with a variety of anilines, mono-substituted
RC6H4NH2, R = H, 4-CN, 4-NO2, 4-Ph, 4-Me, 4-MeO, 4-Me2N; R2C6H3NH2; di-substituted R2 = 3,5-(CH3)2, 3,5-
(CF3)2; R3C6H2NH2; tri-substituted R3 = 3,5-Me2-4-Br; and a “super bulky” aniline (Ar*NH2) [Ar* = 2,6-
bis(diphenylmethyl)-4-tert-butylphenyl], led to the immediate formation of a range of products dependent upon the
substituent. With electron-withdrawing substituents, previously unknown diamines, RC6H4NH(CH2NMe2) [R = CN
(2a), NO2 (2b)] and R2C6H3NH(CH2NMe2) [R2 = 3,5-(CF3)2 (2c)] were formed. Further reaction of 2a, b, c with 1
yielded the corresponding triamines RC6H4N(CH2NMe2)2 (R = CN (3a), NO2 (3b) and R2C6H3N(CH2NMe2)2, R2 =
3,5-(CF3)2 (3c). The new polyamines were characterized by NMR spectroscopy, and for 2a, 2c, and 3c, by single
crystal XRD. In the case of electron-donating groups, R = 4-OMe, 4-NMe2, 4-Me, 3,5-Me2, 3,5-Me2-4-Br, and for R
= 4-Ph, the reactions with 1 immediately led to the formation of the related 1,3,5-triazines, R = 4-MeO (5a), 4-Me2N
(5b), 4-Ph (5c), 3,5-Me2 (5d), 3,5-Me2-4-Br (5e), 4-Ph (5f), 4-Cl (5g). The “super-bulky” aniline rapidly produced a
single product, namely the corresponding imine Ar*N=CH2 (4) which was also characterized by single crystal XRD.
Imine 4 is both thermally and oxidatively stable. All reactions are very fast, thus based upon the presence of Si we are
tempted to denote the reactions of 1 as examples of Silick Chemistry.
Introduction
We recently reported that Et SiOCH NMe ( ) is a highly efficient Mannich reagent, with
1
3
2
2
the ability to transform a range of RE-H species, E = O, S, N, P, to the corresponding
dimethylamino derivatives, RE-CH2NMe2, under mild conditions, and generally without the need
for either a catalyst or activating co-reagent.1,2 In each case Et3SiOH is formed which is easily
removed under vacuum. In the case of the reaction of with aniline the final product obtained was
1
hexahydro-1,3,5-triphenyl-1,3,5-triazine, (PhNCH2)3. However, via NMR spectroscopy we were
able to observe the transience of the previously unreported triamine, (Me2NCH2)2NPh and to trap,
and characterize, its Mo(CO)4 derivative. The overall mechanism proposed for the 1,3,5-triazine
formation is outlined in Scheme 1.
1
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NH2
+ Et3SiOCH2NMe2
- Et3SiOH
Ph
N
5
CH2NMe2
1/3
N
N
N
2
H
Ph
Ph
- Et3SiOH
CH2NMe2
CH2NMe2
4
N
3
N=CH2
(Me2N)2CH2
Scheme 1
We now report the impact upon this chemistry effected by using variously-substituted
anilines, RnC6H5-nNH2, R = H, 4-CN, 4-NO2, 4-Me, 4-Ph, 4-MeO, 4-Me2N; R2C6H3NH2; R2 = 3,5-
(CH3)2, 3,5-(CF3)2; R3C6H2NH2, R3 = 3,5-Me2-4-Br; and a “super-bulky” aniline Ar*NH2 [Ar* =
2,6-bis(diphenylmethyl)-4-tert-butylphenyl].3 This group of amines range from significantly
electron-rich to electron-poor materials, coupled with a specific sterically demanding material.
Overall we observe that electron-withdrawing groups do not go through the complete pathway
1
to and yield only the previously unreported thermally stable diamine ( ) and triamine ( )
5
2
3
materials. On the other hand, the electron-donating substituents progress directly to the 1,3,5-
triazines ( ) with little or no observation of the intermediate diamines and triamines. All materials
5
were formed in good yield, have been characterized, and selected unreported diamines, triamines
and a triazine have been structurally characterized by single crystal XRD. In the case of the super
bulky aniline only a single product was obtained in high yield, the imine Ar*N=CH ( ) which we
4
2
2
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also characterized by single crystal XRD, thus completing the characterization of each of the
materials , , and suggested in Scheme 1.
2 3 4
5
Results and Discussion
Trimethylsiloxymethyl-N,N-dimethylamine, Me3SiOCH2NMe2, was first reported by the
Mironov Group in 1981, prepared from the reaction of Me2NSiMe3 and formaldehyde.4 They
further demonstrated that this material reacted with halosilanes, R3SiX, to form Me2NCH2X and
the corresponding disiloxane, (Me3Si)2O. More interestingly, they noted that its reaction with
excess silylamine led to the formation of diamines and disiloxane (presumably via condensation
of initially formed Me3SiOH), eq. 1a. Furthermore, its reaction with a hydroaminosilane,
BuNHSiMe3, led to a hexahydro-1,3,5-tributyl-1,3,5-triazine, eq. 1b.5
Me3SiOCH2NMe2 + Me3SiNMe2 → Me2NCH2NMe2 + Me3SiOSiMe3 (1a)
3 Me3SiOCH2NMe2 + 3 Me3SiNHBu → (BuNCH2)3 + 1.5 Me3SiOSiMe3 (1b)
These results suggested that could be an excellent CH NMe transfer agent, Mannich
1
2
2
reagent, toward a variety of E-H bonds, E = O, S, N, P and Csp2. Indeed we have reported such
chemistry where , which in our hands is preferably synthesized from the Mo-catalyzed reaction
1
of Et3SiH and DMF,6 can react rapidly and efficiently at low temperature, and without catalysts,
to perform such transfers. We have used the system with secondary amines to form a series of
unusual diamines and reported a single reaction with aniline.2 The latter reaction resulted in good
yields of the hexahydro-1,3,5-triphenyl-1,3,5-triazine, presumably via the transformation in
Scheme 1.
3
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There are many routes in the literature reporting efficient formation of triazines,7 and such
materials and their derivatives have considerable utility as organic synthons and reagents,8 polymer
precursors for resins,9 and materials with significant biological utility.10 Of particular interest was
a recent article from the IBM Almaden laboratory presenting both experimental and theoretical
studies on the formation of hexahydrotriazines.11 Using a high temperature (185o) reaction between
amines, paraformaldehyde and water, the authors clearly noted that depending upon the substituent
on the starting amines, either hexahydro-1,3,5-triazines or hemiaminals were produced. In the case
of p-Me2N-aniline a high yield (88%) of the triazine was obtained, whereas for aniline itself and
p-NO2-aniline only trace amounts of the triazine were noted, 2-3%, whereas 80% of the products
were the appropriate hemiaminals. The authors performed some computational studies on the
system to model the transformation mechanism and their calculations corroborated triazine vs
hemiaminal formation for electron-donating groups, and vice versa for the electron-withdrawing
groups. A similar behavior was reported by Rivera et al. for the formation of triazines via reaction
of anilines with 1,3,6,8-tetraazatricyclo[4.4.1.13,8]dodecane.7d
Given the very efficient chemistry we have observed for the CH2NMe2 transfer chemistry
using , it was of interest to observe the results of the reactions between and substituted anilines
1
1
to see if they also had a significant product distribution even though the chemistry pathway is very
different to the IBM chemistry. Thus, we have reacted with RC H NH , R = H, 4-CN, 4-NO , 4-
1
6
4
2
2
Ph, 4-Me, 4-MeO, 4-Me2N, the bis- and tris-substituted anilines, R2C6H3NH2, R2 = 3,5-CH3, 3,5-
(CF3)2, R3C6H2NH2, and the “super bulky” aniline (Ar*NH2) [Ar* = 2,6-bis(diphenylmethyl)-4-
tert-butylphenyl]. It is important to note that all reactions were fast: no heating was needed and no
catalytic system was added. In keeping with the theoretical predictions noted above, in the case of
the strong-electron-donating substiuents R = 4-MeO, 4-Me2N, 4-Me, R2= 3,5-Me2 and 3,5-Me2-4-
4
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Br, the approriate triazines were formed in high yield, eq. 2. The 4-Cl aniline also produced a
triazine contrary to expectation.
R
NH2
N
+
3 Et3SiOCH2NMe2
(2)
3
- 3 Et3SiOH
N
N
R
R
R
R = 4-MeO (5a); 4-Me2N (5b); 4-Me (5c); 3,5-Me2 (5d); 3,5-Me2-4-Br (5e); 4-Ph (5f); 4-Cl (5g)
The structure of a new triazine material, hexahydro-1,3,5-(3,5-dimethyl-4-bromophenyl)-
1,3,5-triazine, 5e, is illustrated in Figure 1, and is the first of this class of material to exhibit a
Figure 1. Structure of 5e (CCDC 1891888)
boat conformation, with two of the substituents in an axial position and one in equatorial. All
previously reported 1,3,5-hexahydrotriazine structures exhibited a chair conformation.12 However,
for systems with substituted C atoms, e.g. trans-2,4,6-trimethoxy-1,3,5-trinitrotrihydro-1,3,5-
triazine a boat conformation was observed, although the cis isomer crystallized in a chair
conformation.13
5
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Diamine and triamine formtion
Using the anilines containing electron-withdrawing groups, R = 4-CN, 4-NO2, R2 = 3,5-
(CF3)2, we observed no significant hexahydro-1,3,5-triazine formation and only high yields of the
corresponding, and unknown, diamines and triamines, eq. 3.
Me
N
Me
N
H
N
NH2
Me
CH2
N
Me
N
1
Me
(3)
+ 1
CH2
- Et3SiOH
- Et3SiOH
Me
CH2
R
R
2
3
R
R = 4-CN (2a/3a), 4-NO2 (2b/3b), 3,5-(CF3)2 (2c/3c)
Since the occurrence of non-symmetrical diamines and triamines is not well-established,
we have examined the structural properties of selected compounds using single crystal XRD. The
structures of the diamines 4-(CN)C6H4NH(CH2NMe2) [2a], 3,5-(CF3)2C6H3NH(CH2NMe2) [2c],
and triamine 3,5-(CF3)2C6H3NH(CH2NMe2) [3c] are illustrated in Figure 2.
6
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Figure 2. Structure of 2a (top left, CCDC 1891885), 2c (top right, CCDC 1891887), and 3c
(bottom, CCDC 1891886). For 3c one conformer is shown and disorder is omitted for clarity.
For the diamine 2c we can observe the conjugation of N(1) with the ring as shown by the
C-N-C angle of 123.0(4)° and the shorter N-Caryl distance of 1.385(5)Å compared to the N-CH2
bond of 1.438(5)Å. The system is a little out of the plane with respect to the aryl group by 22.5(4)°
(C-C-N-C). Nirogen atom N(2) on the other hand is pseudo-tetrahedral with the distances N-C
averaging 1.467(9)Å. Compound 2a has geometrical parameters similar to those of 2c; however,
the dihedral angle (C-C-N-C) is significantly reduced to 5.7(6)° suggesting packing effects.
For the triamine 3c the N-aryl conjugation is again apparent as shown by the angles C-N-
C of 120.0(5)°, the C-N distances are also the same within the experimental error. However, the
steric congestion is increased, and although this is not reflected in the bond lengths and angles, it
does impact the crystal structure by including two conformers in the asymetric unit cell in
comparison to only one for 2c. The CF3 groups present a disorder that was not observed for 2c
indicating that the packing is more efficient for the latter, a fact corroborated by the calculated
density, 1.402 g/cm3 for 3c vs 1.549 g/cm3 for 2c.
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Imine formation
Finally we have been able to observe, isolate and structurally characterize an example the
supposed imine intermediates in this chemistry by reacting 1 with a “super bulky” aniline, Ar*NH2
[Ar* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl]. The reaction was fast and only a single
product was observable under our reaction conditions; i.e. neither diamine nor triamine could be
detected as a transient and no triazine product was observed. Clearly the extra bulk of the
substituents results in a kinetic stabilization of the imine, an example of such utility of bulky groups
across the chemistry of the elements of the Periodic Table.14 The structure of the imine is presented
in Figure 3.
Figure 3. Structure of 4 (CCDC 1891889).
As expected for the imine structure, the C-N methylene bond is significantly shorter than
the N-Caryl bond, 1.247 Å vs 1.431 Å. Because of the bulky susbtituents the imine is perpendicular
to the aryl plane at 93.6(2) thereby precluding any conjugation. Interestingly in the crystal
°
structure a H-π interaction is observed (3.261 Å) through the CH2 of the imine, generating a chain
on the b axis. The only other such imine structure reported, also with a bulky substituent on
nitrogen, CH2=NAr (Ar = 2,6-(2,4,6-Me3C6H2)2C6H3), also exhibits a similar NH2 group
8
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orthogonal to the aryl group with a similar C-N methylene bond length of 1.247 Å.15 In both the
reported imine and ours, the methylene protons can be noted by 1H NMR spectroscopy as a pair
of doublets, for at 6.12 (1J = 18 Hz) and 7.13 ppm (1JHH = 12 Hz), respectively. Immine ,
4
4
HH
unlike the previously reported example, is a very thermally and oxidatively stable material and its
possible chemical reactivity is currently under investigation.
Experimental
General reaction of anilines and Et3SiOCH2NMe2: In a typical experiment, a Pyrex NMR tube
was charged with 0.200 g, 0.633 mmol of Et3SiOCH2NMe2, 0.316 mmol of NH2Ar-substituted
material, and 0.500 mL of CDCl3 or C6D6 under nitrogen gas atmosphere. The contents were
degassed via three freeze-pump-thaw cycles, and the tube sealed under vacuum. Initial 13C and
1H NMR spectra were obtained after thawing of reaction mixture and the reaction was monitored
at 25 °C by NMR and evaluated for formation of triazines, mono-substituted diamine, or di-
substituted triamines. In the event of formation of a triazine the contents of NMR tube were
decanted into a 5 mL round bottom flask, and solvents and volatile byproducts, (Me2N)2CH2 and
Et3SiOH) were removed by vacuum to leave behind pure triazine solids in 45 - 65% yields.
Hexahydro-1,3,5-(p-methoxyphenyl)-1,3,5-triazine,16 from the reaction of 4-
(methoxy)aniline with Et3SiOCH2NMe2: NMR in CDCl3, 13C: 55.7, 71.3, 114.6, 120.2, 142.8,
154.6. 1H: 3.77 (s, 9 H, CH3), 4.70 (s, 6 H, CH2), 6.79 (d, 6 H, CH), 7.05 (d, 6 H, CH). Melting
point: Melting point: 128 °C (lit. value 128-130 °C).
Hexahydro-1,3,5-(4-dimethylaminophenyl)-1,3,5-triazine),17 from the reaction of 4-
(dimethylamino)aniline with Et3SiOCH2NMe2: NMR in CDCl3, 13C: 4135, 71.7, 114.4, 120.3,
140.8, 146.3. 1H: 2.86 (s, 18 H, CH3), 4.60 (s, 6 H, CH2), 6.72 (d, 6 H, CH), 7.02 (d, 6H, CH).
Melting pointMelting point: 154 °C (lit. value 156 °C)
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Hexahydro-1,3,5-(4-methylphenyl)-1,3,5-triazine,17 from the reaction of 4-methyl-aniline
with Et3SiOCH2NMe2: NMR in C6D6, 13C: 20.6, 69.4, 118.3, 130, 147.2. 1H: 2.08 s, 4.62 s,
6.88 d. Melting point: Melting point: 125 °C (lit. value 126 °C).
Hexahydro-1,3,5-(3,5-dimethylphenyl)-1,3,5-triazine17 from the reaction of 3,5-
dimethylaniline with Et3SiOCH2NMe2: NMR in C6D6, 13C: 21.8, 68.7, 115.9, 122.9, 138.8,
149.4. 1H: 2.10 (s, 18 H, ), 4.66 (s, 6 H, ), 6.41 (d, 4H, ), 6.56 (d, 6H, ). Melting point: 128 °C
(lit. value 128 °C).
Hexahydro-1,3,5-(4-chlorophenyl)-1,3,5-triazine,17 from the reaction of 4-chloroaniline
with Et3SiOCH2NMe2: NMR in CDCl3, 13C: 68.9, 119.18, 126.5, 129.3, 147.2. , 13C: 68.9,
119.18, 126.5, 129.3, 147.2. 1H: 4.80 (s, 6H) 6.90 (d, 6H, ), 7.17 (d, 6H, ). Melting point: 148-
152 °C (lit. value 154 °C).
Hexahydro-1,3,5-(4-1,1’-biphenyl)-1,3,5-triazine:18 1H NMR:  4.94 (N-CH2), 6.64-6.74, 7.04-
7.07, 7.34-7.51 (Ph). 13C NMR: 68.3(CH2), 117.8, 126.6, 127.8, 128.6, 133.8, 140.7, 147.8 (Ph).
Anal. Calcd. for C39H33N3: C, 86.15; H, 6.12. Found: C, 84.70; H, 6.63; Melting point: 148-152
°C
Hexahydro-1,3,5-(4-bromo-3,5-dimethylphenyl)-1,3,5-triazine from the reaction of 4-
bromo-3,5-dimethyl-aniline with Et3SiOCH2NMe2: NMR in CDCl3, 13C: 24.3, 68.7, 117.9,
119.2, 138.9, 147.2. 1H: 2.33 (s, 18 H, CH3), 4.75 (s, 6 H, CH2), 6.68 (s, 6 H, CH). 1H: 2.32 (s,
18 H, CH3), 4.74 (s, 6 H, CH2), 6.67 (s, 6 H, CH). Melting point: 134°C; HRMS 632.999; calcd.
632.9989.
A typical synthesis of a diamine.
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Reaction of Et3SiOCH2NMe2 with 4-cyanoaniline: A Pyrex NMR tube was charged with 0.17
g, 0.9 mmol of Et3SiOCH2NMe2, 0.106 g, 0.9 mmol, of 4-cyanoaniline in 0.5 mL CDCl3. The
tube was sealed under vacuum. An immediate reaction occurred and after 10 minutes monitoring
by 1H, 29Si and 13C NMR spectroscopy showed the formation of diamine and Et3SiOH. The sovent
and the triethylsilanol were removed under vacuum and the residue was extracted with 5 mL of
hexanes and concentrated. Leaving the solution in the refrigerator overnight resulted in the
formation of diamine 2a as a colourless crystals, 0.12 g (68 %).
Synthesis of triamine: Reaction of Et3SiOCH2NMe2 with 4-cyanoaniline (1:2 ratio): In a
typical experiment, a 10 mL round bottom flask was charged with 0.24 g (1.27 mmol) of
Et3SiOCH2NMe2, 0.301 g (2.54 mmol) of 4-cyanoaniline, in 3 mL of CDCl3. The reaction was
29
13
monitored by 1H, Si and C NMR spectroscopy, after 10 minutes of the stirring of reaction
mixture at room temperature, the 13C NMR spectra displayed a major resonance at 67.3 ppm due
to CH2 group indicating the formation of diamine 2a. After 4h of stirring, the resonance at 67.3
ppm due to methylene group of diamine was replaced with a new methylene resonance at 75.3
ppm indicating complete transformation of diamine to triamine 3a. The solvent and triethylsilanol
were removed under vacuum. The residue was extracted with 5 mL of hexanes, concentrated and
left in the refrigerator for recrystallization. A white solid triamine, 0.12 g (41%) yield was
obtained along with 2-3 % trace impurity of diamine. Recrystallization from hexane/CH2Cl2
produced pure material but upon standing in both the solid state and solution, trace amounts of 2a
would be observable. This process resulted in the C and H analyses for triamines to be poor.
Synthesis of triamine: Reaction of Et3SiOCH2NMe2 with 4-cyanoaniline diamine (1:1 ratio):
A Pyrex NMR tube was charged with 0.21 g, 1.1 mmol of Et3SiOCH2NMe2, 0.19 g (1.1 mmol)
of 2a in 0.5 mL CDCl3. The tube was sealed under vacuum. NMR monitoring after 20 minutes of
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reaction by 1H, 29Si and 13C NMR spectroscopy exhibited the complete transformation of diamine
to triamine. The sovent and the triethylsilanol were removed under vacuum. The residue was
extracted with 5 mL of hexanes and recrystallization from hexanes produced triamine, white solid
in 80% yield. All diamine and triamine NMR spectra were recorded in CDCl3.
1
Spectral data for {(3,5-trifluorophenyl)aminomethyl}-dimethylamine: H NMR:  2.27 (s,
6H, CH3), 3.75 (d, 6 Hz 2H, N-CH2), 4.63 (br, 1H, NH), 7.15, 7.04 (3H, Ph). 13C NMR:  43.3
(N-Me), 67.8 (CH2), 110.7 (d, 3.8 Hz), 112.6 (d, 2.8 Hz), 123.5 (q, J = 272.5 Hz).7, 132.0, 132.5
(q, J = 32.6Hz), 148.2 (Ph). Anal. Calcd. for C11H12F6N2: C, 46.15; H, 4.23. Found: C, 45.80; H,
4.18.
1
Spectral data for 4-cyanophenyl diamine: H NMR:  1.78 (s, 6H, CH3), 3.28 (d, 6 Hz, 2H,
N-CH2), 4.29 (br, 1H, NH), 6.19, 6.94 (4H, Ph). 13C NMR:  42.3 (N-Me), 67.3 (CH2), 99.4 (CN),
112.9, 114.5, 133.6, 150.9 (Ph). Anal. Calcd. for C10H13N3: C, 68.54; H, 7.48. Found: C, 68.96;
H, 6.87.
1
Spectral data for 4-nitrophenyl diamine: H NMR:  2.28 (s, 6H, CH3), 3.81 (d, 6 Hz, 2H,
13
N-CH2), 5.03 (br, 1H, NH), 8.06, 8.08 (4H, Ph). C NMR:  42.3 (N-Me), 67.3 (CH2), 111.9,
126.2, 138.6, 153.0 (Ph). Anal. Calcd. for C9H13N3O2: C, 55.37; H, 6.71. Found: C, 54.97; H,
6.54.
Spectral data for 3,5-trifluorophenyl triamine: 1H NMR:  2.17 (s, 12H, CH3), 3.86 (s, 4H,
N-CH2), 7.15, 7.00 (3H, Ph). 13C NMR:  42.1 (N-Me), 76.1 (CH2), 110.6, 113.8, 123.8 (CF3, q,
268.4 Hz), 131.5 (q, J = 32.5 Hz), 148.2 (Ph).
Spectral data for 4-cyanophenyl triamine: 1H NMR:  1.88 (s, 12H, CH3), 3.88 (s, 4H, N-
12
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10.1002/chem.201901877
Chemistry - A European Journal
CH2), 6.44, 6.82 (4H, Ph). 13C NMR:  41.7 (N-Me), 75.3 (CH2), 100.6 (CN), 114.7, 120.1, 132.7
152.0 (Ph).
1
Spectral data for 4-nitrophenyl triamine: H NMR:  2.26 (s, 12H, CH3), 3.98 (s, 4H, N-
CH2), 6.98, 8.14 (4H, Ph). 13C NMR:  42.1 (N-Me), 75.8 (CH2), 111.9, 113.1, 125.4, 152.7 (Ph).
Synthesis of imine 5, Ar*N=CH2, Ar* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl.
A 25 mL round bottom flask was charged with 0.480 g (2.54 mmole) of Et3SiOCH2NMe2 and
0.612 g (1.27 mmol) of Ar*NH2 in 13 mL of methylene chloride at room temperature. The
reaction was stirred and monitored by 1H and 13C NMR spectroscopy. After 15 minutes the
reaction was heated to 60°C in an oil bath. After 3 hours the the reaction cooled to room
temperature and all volatiles were removed under vacuum. A white solid was obtained and
identified by NMR as the imine. Recrystallization from hexane/CH2Cl2 reflux produced pure
colorless crystals suitable for SC-XRD, 55% yield.. 13C NMR (CDCl3); δ 158.63 (N=CH2),
148.60, 145.85, 144.20, 131.87, 129.72, 128.25, 126.28, 125.42, 51.94 (Ar2C), 34.45 (Me3C),
31.36 (Me). 1H NMR δ 7.24, 7.19, 7.13 (d, 1JHH = 18 Hz) 7.07, 7.06, 6.85, 6.12 (d, 1JHH = 18 Hz),
5.44 (CH), 1.08 (Me). Melting Point: 132°C.
AUTHOR INFORMATION
Corresponding Author
kpannell@utep.edu
Notes
We declare no competing financial interest.
13
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10.1002/chem.201901877
Chemistry - A European Journal
We thank the Welch Foundation for support of this research via
ACKNOWLEDGEMENTS.
Grant # AH-0546. We thank Professor Skye Fortier for a sample of 2,6-bis(diphenylmethyl)-4-
tbutyl-aniline.
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