8
990 J . Org. Chem., Vol. 61, No. 25, 1996
Russell et al.
react. Perhaps the hydrogen abstraction is facilitated by
the electrophilicity of the attacking radical, as illustrated
with saturated aqueous Na
and extraction with CH Cl
and drying over MgSO
products were isolated by flash column chromatography on
silica gel (Merck grade 9385, 230-400 mesh) with hexane-
ethyl acetate as the eluent. Solids were recrystallized from
the same solvent.
2
2
S
2
O
3
, neutralization (if required),
2
, followed by washing with brine
4
. After concentration under vacuum,
in transition state 10 (X ) NCH(Ar)CMe
CMe ).
3
2
or CHCH -
3
ArX:- H• CH dCMe2 HgI+
2
N-(2,2-Dim eth yl-1-ph en ylpr opyl)ben zen am in e (2a). 1H
NMR: δ 0.995 (s, 9 H), 4.031 (s, 1 H), 4.245 (s, 1 H), 6.480 (d,
J ) 7.8 Hz, 2 H), 6.570 (t, J ) 7.2 Hz, 1 H), 7.010 (t, J ) 8.1
Hz, 2 H), 7.15-7.30 (m, 5 H). GC and HRMS: m/ z (relative
1
0
Azobenzene is converted to the hydrazine 11 by pho-
tolysis with t-BuHgCl/KI (reaction 4). The reaction does
intensity) 239.1678 (4, calcd for C17
H
21N, 239.1679), 182 (100),
21N: C, 85.31;
hν
104 (10), 77 (19), 57 (2). Anal. Calcd for C17
H
PhNdNPh + t-BuHgI/HI
9
8
H, 8.84; N, 5.85. Found: C, 85.20; H, 8.91; N, 5.83.
0
PhN(t-Bu)NHPh + Me CdCH + Hg + HgI (4)
4-[2,2-D im e t h y l-1-(p h e n y la m in o )p r o p y l]b e n zo n i-
2
2
2
1
1
1
tr ile (2b). Mp: 159-160 °C. H NMR: δ 0.99 (s, 9 H), 4.08
(
d, J ) 5.4 Hz, 1 H), 4.26 (br d, J ) 5.1 Hz, 1 H), 6.43-6.40
not appear to be promoted by PTSA, and the best yield
of 11 (90%) is achieved by photolysis of a mixture of 4
(m, 2 H), 6.62 (t, J ) 7.2 Hz, 1 H), 7.07-7.02 (m, 2 H), 7.43 (d,
13
J ) 8.4 Hz, 2 H), 7.57 (d, J ) 8.1 Hz, 2 H). C NMR: δ 26.93
(
(
q), 34.93 (s), 67.07 (d), 110.73 (s), 113.08 (d), 117.54 (d), 118.91
s), 129.10 (d), 129.14 (d), 131.56 (d), 146.89 (s), 147.20 (s). GC
equiv each of t-BuHgI and KI with 2 equiv of K
p,p′-Dicyanoazobenzene is more reactive, and good yields
of 12 are obtained upon photolysis in Me SO with 4 equiv
of t-BuHgI in the presence of 4 equiv of KI (87% in 19 h),
while addition of 2 equiv of K gives a 97% yield of
2 in 5 h of photolysis. Di-tert-butylated products are
2 2 8
S O .
and HRMS: m/ z (relative intensity) 264.1627 (5, calcd for
, 264.1632), 207 (100), 104 (5), 77 (10). Anal. Calcd
: C, 81.78; H, 7.62; N, 10.60. Found: C, 82.12;
2
18 20 2
C H N
for C18
20 2
H N
2
2 8
S O
H, 7.79; N, 10.40.
1
N-[1-(4-Ch lor op h en yl)-2,2-d im et h ylp r op yl]b en zen a -
1
m in e (2c). Mp: 95-96 °C. H NMR: δ 0.96 (s, 9 H), 4.00 (s,
1
H), 4.20 (s, 1 H), 6.45 (d, J ) 8.1 Hz, 2 H), 6.60 (t, J ) 8.1
13
Hz, 1 H), 7.04 (t, J ) 8.1 Hz, 2 H), 7.23 (br s, 4 H). C NMR:
δ 26.97 (q), 34.82 (s), 66.62 (d), 113.13 (d), 117.15 (d), 127.87
(
d), 129.01 (d), 129.71 (d), 132.39 (s), 169.69 (s), 147.32 (s). GC
and HRMS: m/ z (relative intensity) 273.1291 (2, calcd for
20ClN, 273.1284), 216 (100), 104 (10), 77 (18). Anal. Calcd
for C17 20ClN: C, 74.57; H, 7.36; N, 5.12. Found: C, 73.45;
17
C H
not observed, even under conditions that would favor a
high flux of t-Bu , i.e., with I and S
of radicals such as ArCH(t-Bu)NPh and ArN(t-Bu)NPh
with t-Bu appear to form only the disproportionation
products in which the anilino radical has been reduced.
On the other hand, 5-methylbenzimidazole gives rise to
the oxidative tert-butylation product 13 under all condi-
tions employed. Photolysis of the imidazole with t-
H
•
-
2-
2
•
O
8
. The reactions
H, 7.14; N, 4.90.
•
N-[1-(4-Br om op h en yl)-2,2-d im et h ylp r op yl]b en zen a -
•
1
m in e (2d ). Mp: 91-92 °C. H NMR: δ 0.96 (s, 9 H), 3.98 (s,
1
H), 4.20 (s, 1 H), 6.42-6.45 (m, 2 H), 6.60 (t, J ) 7.2 Hz, 1
H), 7.04 (dd, J ) 8.4, 7.5 Hz, 2 H), 7.17 (d, J ) 8.4 Hz, 2 H),
7.39 (d, J ) 8.4 Hz, 2 H). GC and HRMS: m/ z (relative
intensity) 317.0780 (7, calcd for C17
H
20BrN, 317.0779), 260
20BrN: C, 64.16;
(100), 180 (15), 104 (46). Anal. Calcd for C17
H
H, 6.33; N, 4.40. Found: C, 63.78; H, 6.05; N, 4.27.
N-[2,2-Dim et h yl-1-(4-m et h ylp h en yl)p r op yl]b en zen a -
1
m in e (2e). Mp: 67-68 °C. H NMR: δ 0.95 (s, 9 H), 2.29 (s,
3
H), 4.00 (d, J ) 6.3 Hz, 1 H), 4.22 (d, J ) 6.0 Hz, 1 H), 6.47
(
dd, J ) 8.4, 0.9 Hz, 2 H), 6.56 (tt, J ) 7.5, 0.9 Hz, 1 H), 7.04
13
(
m, 4 H), 7.17 (d, J ) 8.1 Hz, 2 H). C NMR: δ 21.05 (q),
7.04 (q), 34.84 (s), 66.81 (d), 113.09 (d), 116.74 (d), 128.30
d), 128.33 (d), 128.93 (d), 136.11 (s), 137.94 (s), 147.73 (s).
HRMS: m/ z 253.1834 (calcd for C18 23N, 253.1830). Anal.
Calcd for C18 23N: C, 85.32; H, 9.15; N, 5.53. Found: C, 84.06;
2
(
BuHgCl (4 equiv, 7 h) yields only traces of 13, but with
4
2 2 8
equiv of KI the yield of 13 is 55%. Addition of K S O
H
does not increase the yield of 13, while the presence of 4
equiv of PTSA decreases the yield of 13 to 35%, possibly
because of electrophilic cleavage of t-BuHgI. If interac-
H
H, 9.07; N, 5.32.
N-[1-(4-Met h oxyp h en yl)-2,2-d im et h ylp r op yl]b en zen -
a m in e (2f). Mp: 102-103 °C. H NMR: δ 0.92 (s, 9 H), 3.79
•
tion of the adduct radical with t-Bu is important in the
1
formation of 13, it must now occur with transfer of the
(
s, 3 H), 3.98 (d, J ) 5.1 Hz, 1 H), 4.21 (d, J ) 5.1 Hz, 1 H),
•
hydrogen atom from the adduct radical to t-Bu with
6.47 (dd, J ) 8.7, 0.9 Hz, 2 H), 6.58 (tt, J ) 7.5, 0.9 Hz, 1 H),
6.81 (d, J ) 8.7 Hz, 2 H), 7.04 (dd, J ) 8.7, 7.5 Hz, 2 H), 7.20
(
rearomatization of the imidazole ring.
1
3
d, J ) 8.7 Hz, 2 H). C NMR: δ 26.98 (q), 34.91 (s), 55.03
q), 66.49 (d), 113.01 (d), 113.11 (d), 116.73 (d), 128.90 (d),
(
Exp er im en ta l Section
1
29.27 (d), 132.99 (s), 147.70 (s), 158.30 (s). GC and HRMS:
m/ z (relative intensity) 269.1787 (3, calcd for C18
269.1780), 212 (100), 197 (2), 168 (4), 104 (17). Anal. Calcd
H
23NO,
Gen er a l Meth od . NMR spectra were recorded in CDCl
3
1
at 300 MHz for H with TMS as an internal standard and at
1
3
for C H23NO: C, 80.25; H, 8.61; N, 5.20. Found: C, 80.09;
7
5.4 MHz for C with the central line of CDCl
3
the standard
18
H, 8.98; N, 5.11.
(77.00 ppm). GC/MS were recorded with Finnegan 4000 and
Magnum spectrometers and HRMS with a Kratos MS-50
spectrometer. Melting points are uncorrected. Elemental
analyses were performed by Galbraith Laboratories, Inc.
N-[1-(4-Cyan oph en yl)-2,2-dim eth ylpr opyl]-4-cyan oben -
1
zen a m in e (2g). Mp: 178-179 °C. H NMR: δ 1.01 (s, 9 H),
4.13 (d, J ) 6.3 Hz, 1 H), 4.78 (d, J ) 6.0 Hz, 1 H), 6.41 (d, J
) 9.0 Hz, 2 H), 7.31 (d, J ) 8.7 Hz, 2 H), 7.40 (d, J ) 8.4 Hz,
Reactions were monitored on a 0.05 mmol scale under N
in 0.5 mL of Me SO-d in Pyrex NMR tubes with irradiation
2
1
3
2
6
2 H), 7.61 (d, J ) 8.4 Hz, 2 H). C NMR: δ 26.68 (q), 34.81
(s), 66.30 (d), 98.68 (s), 110.94 (s), 112.69 (d), 118.61 (s), 120.22
(s), 128.94 (d), 131.65 (d), 123.34 (d), 145.65 (s), 150.12 (s).
by a 275 W Sylvania sun lamp ca. 25 cm from the reaction
tube. Toluene or diiodomethane was added as an internal
standard before the yield was measured by NMR integration.
Products were isolated on a 0.2 mmol scale from reactions
HRMS: m/ z 289.1575 (calcd for C19
Calcd for C19 : C, 78.86; H, 6.62; N, 14.52. Found: C,
78.58; H, 6.68; N, 14.25.
19 3
H N , 289.1579). Anal.
19 3
H N
2
in 2 mL of deoxygenated Me SO under nitrogen by treatment