The Journal of Organic Chemistry
ARTICLE
Synthesis of 4d. A solution of free carbene 1 (87.1 mg, 0.20 mmol)
and 4-cyanophenyl azide (34.6 mg, 0.24 mmol) in dry THF (2 mL) was
stirred at 23 °C for 12 h. The residual solvent was then removed under
reduced pressure, and the crude product was purified by column
chromatography (SiO2; CH2Cl2) to afford the desired product as a
dark red solid (84.8 mg, 73% yield). Mp: 248-250 °C. Td = 277 °C. 1H
NMR (300 MHz, CDCl3): δ 7.99 (dd, J = 2.4, 8.8 Hz, 2H), 7.70 (dd,
J = 2.4, 9.2 Hz, 2H), 7.34 (d, J = 8.4 Hz, 2H), 7.05 (s, 4H), 6.68 (d, J = 8.8
Hz, 2H), 2.40 (s, 6H), 2.15 (s, 12H). 1H NMR (400 MHz, CD2Cl2): δ
8.02 (dd, J = 2.4, 8.8 Hz, 2H), 7.76 (dd, J = 2.4, 9.2 Hz, 2H), 7.41 (d,
J = 8.4 Hz, 2H), 7.13 (s, 4H), 6.69 (d, J = 8.8 Hz, 2H), 2.47 (s, 6H), 2.18
(s, 12H). 13C NMR (100 MHz, CD2Cl2): δ 174.3, 154.0, 153.0, 140.0,
135.0, 134.5, 132.7, 132.4, 131.9, 129.7, 129.0, 126.7, 122.7, 119.4, 110.2,
21.3, 18.0. HRMS: m/z calcd for C36H31N6O2 [M þ H]þ 579.2514,
found 579.2503. FT-IR (KBr): νCO 1668 cm-1. Anal. Calcd for
C36H30N6O2: C, 74.72; H, 5.23; N, 14.52. Found: C, 74.48; H, 5.24;
N, 14.24.
Synthesis of 4e. To a Schlenk flask charged with a solution of free
carbene 1 (87.1 mg, 0.20 mmol) in dry THF (2 mL) was added in one
portion a solution of 4-(trifluoromethyl)phenyl azide (0.4 mmol) in dry
THF (2 mL). The resulting solution was then stirred at 23 °C for 4 h.
After the residual solvent was removed under reduced pressure, the
crude product was purified by column chromatography (SiO2; 1/2 v/v
hexanes/CH2Cl2) to afford the desired product as a dark red solid
(104.4 mg, 84% yield). Mp: 245-246 °C. Td = 257 °C. 1H NMR (300
MHz, CDCl3): δ 7.99 (dd, J = 2.4, 9.2 Hz, 2H), 7.69 (dd, J = 2.4, 9.2 Hz,
2H), 7.31 (d, J = 9.2 Hz, 2H), 7.05 (s, 4H), 6.73 (d, J = 8.8 Hz, 2H), 2.40
(s, 6H), 2.17 (s, 12H). 1H NMR (400 MHz, CD2Cl2): δ 8.03 (dd, J =
2.4, 9.2 Hz, 2H), 7.75 (dd, J = 2.4, 9.2 Hz, 2H), 7.95 (d, J = 9.2 Hz, 2H),
7.14 (s, 4H), 6.75 (d, J = 8.8 Hz, 2H), 2.47 (s, 6H), 2.20 (s, 12H). 13C
NMR (100 MHz, CD2Cl2): δ 174.3, 153.6, 153.0, 139.9, 135.1, 134.5,
132.5, 131.9, 129.7, 129.0, 128.9, 128.6, 126.7, 126.1, 125.7, 125.7, 123.4,
122.4, 21.3, 18.1. HRMS: m/z calcd for C36H31F3N5O2 [M þ H]þ
622.2420, found 622.2424. FT-IR (KBr): νCO 1668 cm-1. Anal. Calcd
for C36H30F3N5O2: C, 69.55; H, 4.86; N, 11.27. Found: C, 69.28; H,
4.87; N, 11.16.
(d, J = 8.8 Hz, 4H), 2.41 (s, 12H), 2.15 (s, 24H). 13C NMR (100 MHz,
CD2Cl2): δ 165.2, 155.5, 152.9, 146.5, 140.4, 134.8, 131.6, 129.9, 125.7,
124.3, 122.5, 21.3, 18.2. HRMS: m/z calcd for C56H53N12O6 [M þ H]þ
989.4199, found 989.4206. FT-IR (KBr): νCO 1671 cm-1. Anal. Calcd
for C56H52N12O6: C, 68.00; H, 5.30; N, 16.99. Found: C, 68.16; H, 5.43;
N, 16.48.
Synthesis of 5b. To a Schlenk flask charged with a solution of free
carbene 2 (50.0 mg, 0.076 mmol) in dry THF (2 mL) was added in one
portion a solution of phenyl azide (0.22 mmol) in dry THF (2 mL). The
resulting solution was then stirred at 23 °C for 12 h. After the solvent was
removed under reduced pressure, the crude product was purified by
column chromatography (SiO2; 3/1 v/v hexanes/EtOAc) to afford
the desired product as a red-brown solid (60 mg, 88% yield). Mp:
1
244-246 °C. Td = 268 °C. H NMR (300 MHz, CDCl3): δ 7.06
(m, 6H), 6.91 (s, 8H), 6.64 (m, 4H), 2.29 (s, 12H), 2.12 (s, 24H). 1HNMR
(400 MHz, CD2Cl2): δ 7.11-7.09 (m, 6H), 7.05 (s, 8H), 6.59 (dd, 4H),
2.40 (s, 12H), 2.16 (s, 24H). 13C NMR (100 MHz, CD2Cl2): δ 165.6,
152.4, 150.7, 139.9, 135.0, 132.1, 129.7, 128.6, 127.9, 125.4, 122.3, 21.2,
18.2. HRMS: m/z calcd for C56H55N10O2 [M þ H]þ 899.4502, found
899.4504. FT-IR (KBr): νCO 1665 cm-1. Anal. Calcd for C56H54N10O2: C,
74.81; H, 6.05; N, 15.58. Found: C, 75.03; H, 6.06; N, 15.51.
Synthesis of 5c. To a Schlenk flask charged with a solution of free
carbene 2 (35.0 mg, 0.053 mmol) in dry THF (2 mL) was added in one
portion a solution of 4-methoxyphenyl azide (0.28 mmol) in dry THF
(2 mL). The resulting solution was then stirred at 23 °C for 12 h. After
the solvent was removed under reduced pressure, the crude product was
purified by column chromatography (SiO2; first 3/1 v/v hexanes/
EtOAc to remove impurities then 3/2/1 v/v/v hexanes/EtOAc/
CH2Cl2) to afford the desired product as a brown solid (21 mg, 41%
yield). Mp: 260-262 °C. Td = 237 °C. 1H NMR (300 MHz, CDCl3): δ
6.90 (s, 8H), 6.60-6.58 (m, 8H), 3.73 (s, 6H), 2.29 (s, 12H), 2.11 (s,
24H). 1H NMR (400 MHz, CD2Cl2): δ 7.04 (s, 8H), 6.61 (m, 4H), 6.56
(m, 4H), 3.74 (s, 3H), 2.39 (s, 12H), 2.15 (s, 24H). 13C NMR (100
MHz, CD2Cl2): δ 165.7, 159.7, 151.9, 144.5, 139.8, 135.1, 132.0, 129.6,
125.3, 123.6, 113.7, 55.6, 21.2, 18.2. HRMS: m/z calcd for C58H59N10O4
Synthesis of 4f. To a Schlenk flask charged with a solution of free
carbene 1 (87.1 mg, 0.20 mmol) in dry THF (2 mL) was added in one
portion a solution of 4-chlorophenyl azide (0.4 mmol) in dry THF
(2 mL). The resulting solution was then stirred at 23 °C for 12 h. After
the residual solvent was removed under reduced pressure, the crude
product was purified by column chromatography (SiO2; CH2Cl2) to
afford the desired product as a dark violet solid (108.4 mg, 92% yield).
Mp: 239-242 °C. Td = 267 °C. 1H NMR (300 MHz, CDCl3): δ 8.02
(dd, J = 2.4, 9.2 Hz, 2H), 7.73 (dd, J = 2.4, 8.8 Hz, 2H), 7.08 (s, 4H), 7.07
(d, J = 8.8 Hz, 2H), 6.63 (d, J = 8.8 Hz, 2H), 2.44 (s, 6H), 2.21 (s, 12H).
1H NMR (400 MHz, CD2Cl2): δ 8.00 (dd, J = 2.4, 9.2 Hz, 2H), 7.73 (dd,
J = 2.4, 8.8 Hz, 2H), 7.11 (s, 4H), 7.09 (d, J = 8.8 Hz, 2H), 6.58 (d, J = 8.8
Hz, 2H), 2.46 (s, 6H), 2.18 (s, 12H). 13C NMR (100 MHz, CD2Cl2): δ
174.3, 152.7, 149.5, 139.8, 135.2, 134.4, 133.0, 132.6, 131.9, 129.6, 129.0,
128.7, 126.6, 123.6, 21.3, 18.1. HRMS: m/z calcd for C35H31N5O2Cl
[M þ H]þ 959.4711, found 959.4715. FT-IR (KBr): νCO 1664 cm-1
.
Anal. Calcd for C58H58N10O4: C, 72.63; H, 6.10; N, 14.60. Found: C,
72.34; H, 6.21; N, 14.08.
’ ASSOCIATED CONTENT
S
Supporting Information. Figures giving cyclic voltam-
b
mograms, UV-vis spectroelectrochemical data, and NMR spec-
tra. This material is available free of charge via the Internet at
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: bielawski@cm.utexas.edu.
[M þ H]þ 588.2170, found 588.2161. FT-IR (KBr): νCO 1664 cm-1
.
Anal. Calcd for C35H30N5O2Cl: C, 71.48; H, 5.14; N, 11.91. Found: C,
71.46; H, 5.06; N, 11.67.
’ ACKNOWLEDGMENT
Synthesis of 5a. Free carbene 2 (50.0 mg, 0.076 mmol),
4-nitrophenyl azide (29.0 mg, 0.17 mmol), and dry THF (2 mL) were
added to an oven-dried Schlenk flask. The resulting solution was then
stirred at 23 °C for 12 h. The residual solvent was then removed under
reduced pressure, and the crude product was triturated with hexanes
(3 ꢀ 25 mL) and Et2O (3 ꢀ 25 mL) to afford the desired product as a
dark red orange solid (39 mg, 52% yield). Mp: 252-253 °C. Td =
294 °C. 1H NMR (300 MHz, CDCl3): δ 7.91 (d, J = 8.8 Hz, 4H), 6.95
This work was made possible by the generous financial
support of the National Science Foundation (Grant Nos.
CHE-0645563 and CHE-0749571 to C.W.B. and J.L.S., re-
spectively) and the Robert A. Welch Foundation (Grant Nos.
F-1621 and F-1018 to C.W.B. and J.L.S., respectively). Support
from the Korean WCU program (grant R32-2008-000-10217-0)
is also acknowledged. We thank Prof. A. G. Tennyson for
assistance with the spectroelectrochemical experiments and for
insightful discussions.
1
(s, 8H), 6.68 (d, J = 8.8 Hz, 4H), 2.32 (s, 12H), 2.11 (s, 24H). H
NMR (400 MHz, CD2Cl2): δ 7.93(d, J = 8.8 Hz, 4H), 7.07 (s, 8H), 6.66
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dx.doi.org/10.1021/jo200139f |J. Org. Chem. 2011, 76, 3239–3245