9-Boraanthracene, 5-Boranaphthacene, and 6-Borapentacene
(C7/10), 127.4 (C7/10), 126.3 (C8/9), 126.2 (C3), 125.7 (C11), 125.6 (C8/9), 46.9
FULL PAPER
m/z (%): 564 (5) [M+], 387.5 (20), 227.9 (100) [MÀH2IMes+H2]; HRMS
(EI+ TOF): m/z calcd for C38H37N211B [M+]: 532.3050; found: 532.3030;
elemental analysis calcd (%) for C38H37BN2: C 80.85, H 6.61, N 4.96;
found: C 80.11, H 7.18, N 4.80 (mix of TGT and O2 adduct).
(3J
N
(119Sn,C)=370, 1J
ACHUTGTNRENNUG ACHUTGNTREN(NUNG 117Sn,C)=
363 Hz, SnACHTUNGTRENNUNG
LRMS (EI): m/z (%): 366 (12, 8 lines) [M+], 351 (50, 8 lines) [M+
ÀCH3], 215 (100) [M+ÀSn
(CH3)2]; HRMS (EI+ TOF): m/z calcd for
ACHTUNGTRENNUNG
Synthesis of stannacycle 3c: Bis(3-bromo-naphthalen-2-yl)methane
(5.4 g, 12.7 mmol) was dissolved in THF (50 mL) and added dropwise to
a stirring slurry of Mg (1.85 g, mmol, activated by I2) in THF at reflux.
The rate of addition was such that the reaction maintained a steady
reflux. During this time the reaction turned dark green. After 1 h, GCMS
analysis of a quenched aliquot showed only one peak for debrominated
starting material. The reaction mixture was further diluted with an addi-
tional THF (30 mL), cooled to room temperature, and Me2SnCl2 (2.93 g,
mmol) dissolved in THF (40 mL) was added by slow dropwise addition.
After stirring for 2 h at room temperature, the dark solution was
quenched with dilute HCl and extracted with diethyl ether (3ꢃ50 mL)
dried over Na2SO4 to give a tan solid (5.14 g). All of this material was ex-
tracted overnight with hexane by using Soxhlet apparatus to give Sn-con-
taining material (1.11 g). This was further purified by flash chromatogra-
phy with hexane/diethyl ether (30:1) to give reasonably pure material
(1.05 g, 20%). Analytically pure material could be obtained by further
flash chromatography with hexane. 1H NMR (400 MHz, CDCl3): d=8.07
C19H18120Sn [M+]: 366.0430; found: 366.0428.
Synthesis of boracycle 4b: 5,12-Dihydro-5,5-dimethyl-5-stannanaphtha-
cene (750 mg, 2.05 mmol) was dissolved in dichloromethane and cooled
to À788C and excess BCl3 was condensed into the reaction flask. After
30 min at this low temperature the reaction was thick with precipitate
and the cold bath was removed and the reaction was allowed to warm to
room temperature overnight. The volatile compounds were removed in
vacuo and the residual Me2SnCl2 was removed by sublimation to give the
desired product as a white solid (340 mg, 60%). 1H NMR (400 MHz,
CDCl3): d=8.94 (s, 1H; H6), 8.38 (dd, 2J
G
ACHTUNGTRENUN(NG H,H)=1 Hz,
3
4
1H; H4), 8.06 (dd, J
ACHTUNGTRENNUNG(H,H)=8 Hz, JACHTNUGTRENNUNG
H11), 7.87 (d, 3J
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
13C{1H} NMR (100 MHz, CDCl3): d=148.5, 141.9, 138.2 (C6), 136.2, 135.8
(C4), 134.0 (C3), 131.7, 129.9 (C10), 128.7 (C8), 128.3 (C1), 127.4 (C7), 126.2
(C9), 126.0 (C11), 125.8 (C2), 37.8 ppm (C12); 11B{1H} NMR (128 MHz,
CDCl3): d=56.3 ppm; LRMS (EI): m/z (%): 262.1 (50) [M+], 226.1 (50)
[MÀHCl], 149 (100); HRMS (EI+ TOF): m/z calcd for C17H1211BCl [M+]:
262.0721; found: 262.0716.
(s, 2H; H5,7), 7.87 (s, 2H; H12,14), 7.80 (m, 4H; H1,4,8,11), 7.44 (m, 4H;
2
H2,3,9,10), 4.32 (s, 2H H13), 0.72 ppm (m, J
G
N
13C NMR (50 MHz, CDCl3): d=143.6 (m, 2J
G
1
2
139.7 (m, 1J
A
N
(117Sn,C)=423 Hz, C5a,6a), 136.4 (m, J-
Synthesis of carbene adduct 5b: Toluene (20 mL) was condensed into a
flask containing 5-bora-5-chloro-5,12,dihydronaphthacene (320 mg,
1.22 mmol) and 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (448.3 mg,
1.46 mmol) at À788C. Following the addition of solvent, the cold bath
was removed and after stirring for 45 min the volume was reduced in
vacuo and the precipitate was isolated. The crude white solid was washed
with toluene and pentane followed by dichloromethane to give product
of analytical purity (613 mg, 89%). 1H NMR (400 MHz, CDCl3): d=7.58
(Sn,C)=8 Hz, C11a,14a), 132.1 (m, 3J-
ACHTUNGTRENNUNG
3
AHCTUNGTRENNUNG
(Sn,C)=31 Hz, C11,14), 125.6 (C2,10), 47.26 (C13), À9.49 ppm (CH3);
119Sn{1H} NMR (112 MHz, CDCl3): d=À99.0 ppm; LRMS (EI): m/z (%):
415.7 (1) [M+], 400.9 (12) [MÀCH3], 265.1 (35), 149 (50), 45 (100);
HRMS (EI): m/z calcd for C23H20120Sn [M+]: 416.05870; found:
416.05987; elemental analysis calcd (%) for C23H20Sn: C 66.55, H 4.86, N
0; found: C 66.97, H 4.96, N À0.03.
(dm, J
1H; H10), 7.18 (m, 2H; H8,9), 6.95 (dm, J
(dm, J (H,H)=7 Hz, J
(H,H)=8 Hz,1H; H4), 6.77 (dt, J
H2), 6.58 (s, 2H; m-MesH) 6.44 (tm, J(H,H)=8 Hz, 1H; H3), 6.33 (s, 2H;
m-MesH), 4.19 (d, 2J(H,H)=16 Hz, 1H; H12 cis to H2IMes), 3.85 (s, 4H;
NCH2CH2N), 3.81 (d, 2J(H,H)=16 Hz, 1H; H12 cis to Cl), 2.23 (s, 6H;
ACHTUNGTRENNUNG
N
Synthesis of boracycle 4c: Stannacycle (545 mg, 1.3 mmol) was dissolved
in CH2Cl2 (20 mL) on a swivel frit. Excess BCl3 gas was condensed in at
À788C and the reaction was left to stir for 30 min at low temperature. At
this time, the cold bath was removed and the reaction was allowed to
slowly warm to room temperature. During this time the reaction turned
grey as a precipitate became clearly visible. All volatile compounds were
removed in vacuo and hexane was condensed in. Sonication resulted in a
heterogeneous mixture that was separated by filtration. All solids were
washed with several portions of hexane to give a grey solid. Isolation of
the solid material afforded very pure product with traces of Me2SnCl2
(380 mg). Residual Sn impurities were removed under dynamic vacuum
to give the material (350 mg, 86%). 1H NMR (300 MHz, [D8]THF): d=
4.29 (s, 1H; H13), 7.36 (m, 4H; H2,3,9,10), 7.73 (s, 2H; H12,14), 7.75 (d, 3J-
A
R
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
MesCH3), 2.19 (s, 6H; MesCH3), 2.02 ppm (s, 6H; MesCH3);
13C{1H} NMR (100 MHz, CDCl3): d=142.2, 141.2, 134.2, 133.4 (C4), 133.2
(C6), 132.3, 132.1, 129.4 (m-MesC), 129.3, 129.1 (m-MesC), 128.5 (C10),
126.5 (C7), 125.3 (C1), 124.6 (C3), 124.5 (C2), 124.0 (C8/9), 123.4 (C8/9),
122.8 (C11), 51.1 (NCH2CH2N), 42.6 (C12), 20.9 (p-MesCH3), 18.3 ppm (o-
MesCH3); 11B{1H} NMR (128 MHz, CDCl3): d=À6.5; LRMS (EI): m/z
(%): 567.8 (25) [M+], 532.9 (30) [MÀCl], 446.8 (28) [MÀMes], 304.9
(100) [H2IMes]; HRMS (EI+ TOF): m/z calcd for C38H3811BN2Cl [M+]:
568.2817; found: 568.2790; elemental analysis calcd (%) for
C38H38BN2Cl: C 80.21, H 6.73, N 4.92; found: C 80.04, H 7.02, N 4.77.
ACHUTNGRENNUG CAHTUNGTRENNUGN
(H,H)= 7.8 Hz, 2H; H1,11), 7.84 (d, 3J(H,H)= 7.9 Hz, 2H; H4,8),
8.43 ppm (s, 2H; H5,7); 13C{1H} NMR (75 MHz, [D8]THF): d=41.4 (C13),
125.0 (C12,14), 125.4, 126.3, 127.8 (C1,11), 129.0 (C4,8), 132.9 (C5,7), 133.5,
134.8, 141.9 ppm, C5a/6a were not observed; 11B{1H} NMR (128 MHz): d=
11.1 ([D8]THF), 53.8 ppm (CDCl3); LRMS (EI): m/z (%): 312.1 (100)
[M+], 276.0 (60) [MÀCl]; HRMS (EI): m/z calcd for C21H14BCl [M+]:
312.0877; found: 312.0853; elemental analysis calcd (%) for C21H14BCl: C
80.69, H 4.51, N 0; found: C 78.08, H 4.45, N À0.03.
Synthesis of 5-boranaphthacene 6b: 5-Bora-5-chloro-5,12-dihydro-6-(3-
dimesityl-4,5-dihydroimidazol-2-ylidene)naphthacene
(300 mg,
0.53 mmol) was suspended in toluene (20 mL) and at À788C LiTMP
(100 mg, 0.8 mmol) dissolved in toluene was added. During the course of
1.5 h, the reaction turned from its initial color of pale yellow to blue-
green to black. At this time the volume was reduced and the blue black
solid was isolated by vacuum filtration. The solid was washed with
hexane and dried in vacuo to afford material of spectroscopic purity
Synthesis of carbene adduct 5c: CH2Cl2 (20 mL) was condensed into a
flask
containing
6-chloro-6,13-dihydro-6-bora-pentacene
(493 mg,
1
(266 mg, 90%). H NMR (400 MHz, CDCl3): d=8.66 (s, 1H; H6), 8.23 (s,
1.6 mmol) and 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene (532 mg,
1.7 mmol) at À788C. Following the addition of solvent, the cold bath was
removed and after stirring for 45 min the volume was reduced in vacuo
and the precipitate was isolated. The crude white solid was washed with
toluene and pentane followed by dichloromethane to give product of an-
alytical purity (911 mg, 92%). 1H NMR (Bruker Avance, 400 MHz, Pyri-
1H; H11), 8.04 (d, J
ACHTUNGTRENNUNG ACHTUNGTRENNUNG
(H,H)=8 Hz, 1H; H4), 7.85 (d, J
H7), 7.76 (d, J(H,H)=8 Hz, 1H; H10), 7.64 (d, J
A
A
7.52 (s, 1H; H12), 7.20 (m, 1H; H9), 7.15 (m, 1H; H8), 7.09 (m, 1H; H2),
6.70 (m, 1H; H3), 6.66 (s, 2H; m-MesH), 6.62 (s, 2H; m-MesH), 4.42 (m,
4H; NCH2CH2N), 2.49 (s, 6H; o-MesCH3), 2.45 (s, 6H; o-MesCH3),
2.01 ppm (s, 6H; p-MesCH3); 13C{1H} NMR (100 MHz, CDCl3): d=139.1,
138.9, 137.4, 135.6, 135.5, 134.9 (C4), 134.4, 133.0 (C6), 133.5, 130.3 (m-
MesCH), 130.1 (m-MesCH), 128.9 (C11), 128.8 (C7), 128.1 (C10), 125.8,
124.9 (C2), 124.7 (C11), 124.1 (C9), 121.7 (C8), 115.0 (C3), 112.3 (C12), 52.9
(NCH2CH2N), 21.0 (p-MesCH3), 20.0 (o-MesCH3), 19.6 ppm (o-
MesCH3); 11B{1H} NMR (128 MHz, CDCl3): d=27.6 ppm; LRMS (EI):
dine-d5): d=7.86 (s, 2H; H5,7) 7.80 (d, 3J
(s, 2H; H12,14), 7.45 (d, 3J(H,H)=7.8 Hz, 2H; H1,11), 7.34 (m, 4H;
(H,H)=15.4 Hz, 1H; H13),
(H,H)=15.4 Hz, 1H; H13), 3.91 (s, 4H; NCH2CH2N), 2.35 (s,
(H,H)=7.9 Hz, 2H; H4,8), 7.62
ACHTUNGTRENNUNG
H2,3,9,10), 6.37 (s, 4H; m-MesH), 4.61 (d, 2J
ACHTUNGTRENNUNG
4.15 (d, 2J
ACHTUNGTRENNUNG
11
12H; o-MesCH3), 1.87 ppm (s, 6H; p-MesCH3);
B{1H} NMR
(128.2 Hz, [D5]pyridine): d=À6.2 ppm; 13C{1H} NMR (100.6 Hz,
Chem. Eur. J. 2010, 16, 12199 – 12206
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
12205