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M. M. Oliveira et al. / Tetrahedron 61 (2005) 1681–1691
4.4.1. 4-Hydroxybenzo[a]carbazole 3a. Light brown
powder. Yield 94%. Mp O250 (lit20 266). 1H NMR
(acetone-d6): 6.92 (1H, dd, JZ7.5, 2.3 Hz), 7.13–7.17
(1H, m), 7.28–7.35 (2H, m), 7.52 (1H, d, JZ7.8 Hz, 7.86
(1H, d, JZ8.2 Hz), 7.96 (1H, d, JZ9.0 Hz), 8.06–8.09 (2H,
m), 9.00 (1H, s, –OH), 11.00 (1H, sl, –NH).
368.0 (6270), 386.0 (7090). 1H NMR: 6.53 (1H, d JZ
10.0 Hz, H-3), 7.07 (1H, t, JZ7,5 Hz), 7.11–7.14 (m, 2H),
7.20–7.26 0(0m,05H), 7.30 (1H, d, JZ8.9 Hz), 7.39–7.41 (4H,
m, H-20, 2 , 6 and 600), 7.45 (1H, d JZ10.0 Hz, H-4), 7.46
(1H, d, JZ8.0 Hz), 7.69 (1H, d, JZ8.9 Hz), 8.00 (1H, d,
JZ7.8 Hz), 8.07 (1H, d, JZ8.8 Hz), 8.26 (1H, d, JZ
8.9 Hz), 11.2 (1H, sl, NH). 13C NMR: 82.3 (C-4), 111.7 (d),
113.4 (d), 115.6 (s), 116.8 (s), 117.2 (d), 117.4 (s), 119.6 (d),
119.9 (d), 120.4 (d), 120.9 (d), 123.9 (s), 124.2 (d), 124.7
(d), 126.9 (4C, C-20, 2000, 60 and 600), 127.8 (2C, C-40 and 400),
128.6 (4C, C-30, 300, 5 and 5000), 128.8 (s), 128.9 (d), 136.7
(s), 139.5 (s), 145.4 (2C, C-1 and 100), 150.4 (s). MS: m/z
(%): 423 (100), 346 (81), 315 (5), 257 (6), 211 (7), 173 (15),
165 (9). Exact mass for C31H21NO: 423.1623. Found
423.1639.
4.4.2. 3-Hydroxybenzo[a]carbazole 3b. Light brown
powder. Yield 94%. Mp O250 (lit23 265).1H NMR
(acetone-d6): 7.22–7.29 (2H, m, H-2 and H-8), 7.38 (1H,
dt, JZ7.5, 1.2 Hz, H-9), 7.42 (1H, d, JZ2.4 Hz, H-4), 7.51
(1H, d, JZ8.7 Hz, H-5), 7.62 (1H, dl, JZ8.1 Hz, H-10),
8.13–8.16 (2H, m, H-6 and H-7), 8.38 (1H, d, JZ9.0 Hz,
H-1), 8.67 (1H, s, –OH).
4.4.3. 2-Hydroxybenzo[a]carbazole 3c. Light brown
powder. Yield 65%. Mp 237–239 (lit23 246). 1H NMR
(acetone-d6): 7.10–7.17 (2H, m), 7.30 (1H, ta, JZ7.7 Hz,
H-9), 7.49–7.53 (2H, m), 7.71 (1H, sl, H-1), 7.84 (1H, dd,
JZ7.7 Hz, 1.1), 7.92 (1H, dd, JZ8.5 Hz, 1.3), 8.06 (1H, d,
JZ7.9 Hz), 8.68 (1H, s, –OH).
4.5.3. 3,13-Dihydro-3,3-diphenyl-1-benzopyran[5,6-
a]carbazole 6. White solid. Yield 77%. Mp 217.3–218.4.
IR: 3425 (NH), 3056, 1450, 1390, 1240, 809, 746, 699. UV–
Vis (closed form): 335.0 (7540), 351.1 (6950), 371.0 (5750),
390.1 (6350). 1H NMR: 6.51 (1H, d, JZ9.8 Hz, H-2), 7.23–
7.30 (3H, m, H-10 or H-11, H-40 and 400), 7.32–7.36 (5H, m,
H-30, 300, 50, 500 and H-7), 7.43 (1H, dt, JZ8.0, 1.2 Hz, H-11
or H-10), 7.59 (1H, d, JZ8.5 Hz, H-5), 7.61–7.64 (4H, m,
H-20, 200, 60, 600), 7.71 (1H, d, JZ8.0 Hz, H-12), 7.91 (1H, d,
JZ8.8 Hz, H-8), 7.99 (1H, d, JZ9.8 Hz, H-1), 8.09 (1H, d,
JZ8.5 Hz, H-6), 8.18 (1H d, JZ8.0 Hz, H-9), 10.82 (1H, sl,
N–H). 13C NMR: 82.2 (C-3), 112.6 (d), 115.3 (s), 117.6 (d),
118.0 (d), 119.8 (s), 120.4 (d), 120.5 (d), 121.5 (s), 121.7
(d), 1020 3.7 (d), 124.1 (s0), 125.7 (d), 127.7 (4C, 0C-20, 200, 0060
and 6 ), 128.3 (2C, C-4 and 400), 128.9 (4C, C-3 , 300, 50, 5 ),
129.0 (d), 129.9 (s), 132.1 (d), 135.1 (d), 140.8 (d), 145.7
(2C, C-10 and 100), 151.9 (s). MS: m/z (%): 423 (100), 346
(40), 315 (5), 257 (9), 228 (6), 212 (7), 191 (6), 173 (8), 165
(11), 77 (5). Exact mass for C31H21NO: 423.1623. Found
423.1610.
4.5. General method for the synthesis of compounds 4–6
A suspension of hydroxybenzo[a]carbazole 3a–c, (2.33 g,
10 mmol) in dry toluene (50 ml), under Ar, was stirred until
all the hydroxybenzocarbazole was dissolved. A solution of
titanium (IV) ethoxide (2.28 g, 10 mmol) in dry toluene
(40 ml) was added over a period of 10 min. The mixture was
refluxed for 30 min, and the ethanol formed was slowly
distilled (up to 1/3 of the initial volume). The mixture was
cooled to r.t. and a solution of b-phenylcinnamaldehyde
(2.08 g, 10 mmol) in 40 ml of dry toluene was added
dropwise. The mixture was refluxed for a period of 2–6 h,
cooled to r.t., quenched with NaOH (2M aq, 40 mL), and
extracted with CH2Cl2 (3!40 ml). The combined organic
extracts were dried (MgSO4), evaporated to dryness and the
residue was purified by CC on silica gel.
Acknowledgements
4.5.1. 5,13-Dihydro-5,5-diphenyl-1-benzopyran[7,8-
a]carbazole 4. Light brown solid. Yield 63%. Mp 230.5–
231.5. IR: 3424 (NH), 3056, 1517, 1490,1457, 1398, 1232,
821, 746, 700. UV–Vis (closed form): 314 (32210), 332
(14020), 347 (12040), 366 (10810), 385 (13860). 1H NMR:
6.46 (1H, d, JZ9.7 Hz,0H-4), 6.91 (1H, d, JZ9.7 Hz, H-3),
7.22–7.270(3H, m, H-4 , 400 and H-12), 7.32–7.42 (6H, m,
H-30, 30,050 , 500, H-10 and H-11), 7.61–7.63 (4H, m, H-20, 200,
60 and 6 ), 7.66 (1H, d, JZ8.3 Hz, H-1), 8.03 (1H, d, JZ
8.3 Hz, H-2), 8.18 (1H, d, JZ7.8 Hz, H-9), 8.22 (1H, d, JZ
8.8 Hz, H-7) and 8.27 (1H, d, JZ8.8 Hz, H-8) AB system,
11.30 (1H, sl, N–H). 13C NMR: 83.8 (C-5), 112.2 (d), 113.9
(d), 115.4 (d), 116.9 (d), 119.4 (s), 120.0(d), 120.3 (d), 120.5
(d), 123.5 (s0)0, 123.8 (s), 124.6 (s), 124.9 (d), 125.6 (d), 127.4
(4C, C-20, 2 , 600 and 6000), 128.3 (2C, C-40 and 400), 128.5 (d),
129.4 (4C, C-3 , 300, 5 and 500), 136.4 (s), 140.3 (s), 146.3
(2C, C-10 and 100), 149.4 (s). MS: m/z (%): 423 (100), 346
(43), 317 (6), 212 (7), 191 (7), 165 (6). Exact mass for
C31H21NO: 423.1623. Found 423.1635.
We are grateful to FCT and FEDER for financial support
through Project POCTI/Qui/38771/2001 and to R. Dubest
and J. Aubard (ESA CNRS 7086, University of Paris VII)
for the evaluation of spectrokinetic parameters by flash
photolysis.
References and notes
1. Bertelson, R. C. In Photochromism; Brown, G. H., Ed.; Wiley:
New York, 1971; Chapter 3, pp 45–431.
2. Van Gemert, B. In Crano, J. C., Guglielmetti, R. J., Eds.;
Organic Photochromic and Thermochromic Compounds;
Plenum: New York, 1999; Vol. 1, Chapter 3, pp 111–140.
3. Crano, J.; Flood, T.; Knowles, D.; Kumar, A.; Van Gemert, B.
Pure Appl. Chem. 1996, 68, 1395–1398.
4.5.2. 4,13-Dihydro-4,4-diphenyl-1-benzopyran[6,5-
a]carbazole 5. White solid. Yield 24%. Mp O 250. IR:
3429 (NH), 1633, 1448, 1384, 1259, 1209, 1058, 809, 750,
698. UV–Vis (closed form): 333.0 (6180), 350.0 (5770),
4. Kumar, A.; Van Gemert, B.; Knowles, D. B. Mol. Cryst. Liq.
Cryst. 2000, 344, 217–222.
5. Van Gemert, B. Mol. Cryst. Liq. Cryst. 2000, 344, 57–62.
6. Kolc, J.; Becker, R. S. J. Phys. Chem. 1967, 71, 4045–4047.