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M. Khandelwal, R.J. Wehmschulte / Journal of Organometallic Chemistry 696 (2012) 4179e4183
[DcpAlEt][CHB11H5Cl6] (Dcp ¼ 2,6-(2,6-Cl2C6H3)2C6H3e), 3 [17],
[Dipp*AlEt][CHB11H5I6] (Dipp* ¼ 2,6-Dipp2C6H3e, Dipp ¼ 2,6-
iPr2C6H3e), 4 [17], DcpAlEt2, 7 [17], and Dipp*AlEt2, 8 [17], were
synthesized according to the literature procedures.
the AlEt3 was consumed (2 d) (The reaction time for this reaction
was rather long due to the use of just an equimolar amount of AlEt3
and crystalline instead of microcrystalline or amorphous trityl
salt.). A small portion of the solution (110 mg, ca. 8
was taken into a separate J. Young type NMR tube, and hexame-
thylbenzene (3 mg, 18 mol) and 2,2-diphenyl-pent-4-en-1-amine
(19 mg, 78 mol) were added. The resulting mixture was heated at
mmol of catalyst)
m
2.2. N-benzyl-4-methyl-2,2-diphenylpent-4-en-1-amine, F
m
135 ꢁC for 70 h while the progress of the reaction was monitored by
1H NMR spectroscopy. Conversion 98% Yield 82% with respect to the
internal reference. For conversion and yield after 30 h see Table 2,
entry B9.
This compound was prepared in analogy to E [21] using A as
a precursor and obtained as a colorless, viscous oil. Yield: 0.58 g,
85%. 1H NMR (400.13 MHz, C6D6): 0.78 (br s, 1H, NH), 1.14 (s, 3H,
Me), 3.08 (s, 2H, CH2), 3.32 (s, 2H, CH2), 3.54 (s, 2H, CH2), 4.82 (s, 1H,
]CH2), 4.90 (s, 1H, ]CH2), 6.98e7.19 (m, 15H, Ph). 13C{1H} NMR
(100.62 MHz, C6D6): 25.1 (Me), 44.9(CH2), 50.8 (CPh2), 54.8(CH2Ph),
55.5(CH2), 115.9(]CH2), 126.6, 127.4,128.5, 128.8, 141.5, 143.3, 147.9.
2.5. [AlEt2{NH2CH2C(Ph)2CH2CHCH2}2][CHB11H5Cl6], 5
A J. Young valve fitted NMR tube was charged with [Ph3C]
[CHB11H5Cl6] (200 mg, 0.34 mmol) and AlEt3 (66 mg, 0.58 mmol) in
benzene (0.8 mL). The suspension was stirred at room temperature
until the red solid turned into a pale white solid. The solid was
washed with hexanes (3 ꢂ 1 mL) and dried (yield: 130 mg,
0.29 mmol, 85%). Benzene (0.8 mL) and NH2CH2C(Ph)2CH2CHCH2, B,
(138 mg, 0.58 mmol) were added to the dry solid. The mixture was
gently heated (80 ꢁC) to obtain a clear solution. The product
precipitated out of the solution upon cooling to room temperature.
Yield 126 mg (0.14 mmol, 50.5%). Mp 155e157 ꢁC. 1H NMR
(400.13 MHz, C6D6): ꢃ0.20 (q, J ¼ 8.2 Hz, 4H, AlCH2CH3), 0.70 (t,
J ¼ 8.1 Hz, 6H, AlCH2CH3), 1.58 (s, 1H, CH-carborane), 2.92 (d,
J ¼ 6.7 Hz, 4H, CH), 3.04 (s, 4H,NH2), 3.2 (s, 4H, CH2) 4.93 (d,
J ¼ 10.2 Hz, 2H, CH’), 5.21 (m, 2H, CH), 5.39 (d, J ¼ 17.0 Hz, 2H, CH),
6.95e6.99 (m, 12H, Ph), 7.07e7.11 (m, 8H, Ph). 13C{1H} NMR
(100.62 MHz, C6D6): ꢃ2.7 (AlCH2CH3), 8.7 (AlCH2CH3), 40.7 (CH2),
48.5 (CH2NH2), 50.9 (C(Ph2)), 120.6(]CH2), 128.9 (Ph), 129.7 (Ph),
130.2 (Ph),133.1(CH),143.4 (Ph).11B NMR (128.38 MHz, C6D6): ꢃ23.1
(d broad, 5B, BH), ꢃ5.3 (s, 5B, m-BCl), 1.1 (s, broad, 1B, p-BCl).
2.3. Hydroamination experiments
For a typical NMR scale experiment, 100
mol of catalyst, 2 mg of 2,6-di-tert-butylpyridine (10
known amount of hexamethylbenzene (2e4 mg,
mol) as internal standard were dissolved in C6D6
m
mol of aminoalkene,
10
and
12e25
m
m
mol)
a
m
(0.8 mL). The solution was transferred into a J. Young valve fitted
NMR tube. The sealed NMR tube was then heated in a tempera-
ture controlled silicone-oil bath at 135(ꢀ2) ꢁC for the specified
amount of time (see Tables 1 and 2), and the reaction progress
was monitored via 1H NMR spectroscopy. All product signals
were in good agreement with previously published data of
identical products [18,20,21,23].
2.4. Hydroamination with in situ generated 1 (entry B9, Table 2)
A mixture of AlEt3 (6 mg, 52
m
mmol), [Ph3C][CHB11H5I6] (62 mg,
54
mol), was heated at 80 ꢁC inside a J. Young type NMR tube until
Table 1
Catalytic hydroamination of aminoalkenes (AeD) by cationic aluminum species (1e4).
Entrya
A1
Substrate
Product
Catalyst
Time (h)
5
% Conversionb
% Yieldb
78
1
>99
A2
A3
2
3
5
86
74
85
34
>99
A4
4
1.5
>99
60
B1
B2
B3
B4
1
28
88
70 þ 15c
70 þ 10c
2
3
39
3
95
>99
83
4
0.25
>99
90
C1
C3
1
3
110
103
89
90
84
85
C4
4
1d
98
88
D1
1
70
0
0
1 ¼ [AlEt2][CHB11H5I6]; 2 ¼ [AlEt2][CHB11H5Cl6]; 3 ¼ [DcpAlEt][CHB11H5Cl6]; 4 ¼ [Dipp*AlEt][CHB11H5I6].
a
All reactions were carried out in C6D6 at 135 ꢁC and 10 mol% catalyst loading.
b
Determined by integration of 1H NMR signals of reactant and product versus an internal standard.
c
Isomerized product.
17.5 mol % catalyst loading in C6D6 at 135 ꢁC.
d