Cycloaddition of Azapropellanes

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Synthesis and Properties of Tribenzocarbazoles via an Acidpromoted Retro (2+2)-Cycloaddition of Azapropellanes Naoki Ogawa, Yousuke Yamaoka, Hiroshi Takikawa, Kazunori Tsubaki, and Kiyosei Takasu J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b00870 • Publication Date (Web): 04 Jun 2018 Downloaded from http://pubs.acs.org on June 4, 2018

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The Journal of Organic Chemistry

Synthesis and Properties of Tribenzocarbazoles via an Acid-promoted Retro (2+2)-Cycloaddition of Azapropellanes Naoki Ogawa,a Yousuke Yamaoka,a Hiroshi Takikawa,a Kazunori Tsubaki,b and Kiyosei Takasua,*

a

Graduate School of Pharmaceutical Sciences, Kyoto University, Yoshida, Sakyo-ku, Kyoto 606-8501, Japan.

b

Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Shimogano, Sakyo-ku, Kyoto 606-8522, Japan.

E-mail: [email protected]

Fax: +81 75 753 4604; Tel: +81 75 753 4553

1 ACS Paragon Plus Environment

The Journal of Organic Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Abstract Graphic

Abstract.

We describe herein the development of a new method to synthesize tribenzocarbazoles via an acid-promoted retro (2+2)-cycloaddition of azapropellanes, which were prepared by potassium hexamethyldisilazide (KHMDS)-promoted (2+2) cyclo-addition. The tribenzocarbazoles showed strong fluorescence both in solution and solid-state. The structural, electronic and optical properties of the synthetic tribenzocarbazoles are also described.

Introduction The carbazole ring represents an important class of N-heterocyclic frameworks. This skeleton is frequently found in natural products and pharmaceuticals.1 Carbazoles and their related compounds exhibit diverse biological activities, such as antitumor, antimicrobial, anti-inflammatory, and neuroprotective effects. They have also attracted considerable attention in materials science, and a variety of carbazoles have proven 2 ACS Paragon Plus Environment

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useful in organic devices such as organic light-emitting diodes (OLEDs),2 organic field-effect transistors (OFETs),3 and solar cells.4 Therefore, much effort has been devoted to the development of new methods to construct carbazole skeletons. Because the introduction of extended π-systems into carbazoles can change the optoelectronic properties,5 the synthesis of benzo-fused carbazoles, mainly via transition metal catalysis, has been a particular focus.6,7,8 Although a number of methods to synthesize monobenzo- and dibenzo-carbazoles have been established, only a few synthetic methods are available to introduce more than three benzo-fused moieties onto the carbazole motif. So that, almost no information about the property of tri- and tetra-benzocarbazoles has been reported. In 2001, Kocovsky and co-workers reported the synthesis of tetrabenzo[a,c,g,i]carbazole via a copper(II)-mediated oxidative homocoupling of 9-aminophenanthrene.9 Ito, Itami et al. recently reported an elegant palladium-catalyzed annulative π-extension (APEX) reaction of heteroarenes,

leading

to

the

successful

synthesis

of

tetrabenzo[a,c,g,i]carbazole.10

Although

tribenzocarbazoles are of interest in organic electronic devices, methods for their synthesis are still limited, presumably because of their unsymmetric fused π-structures. To the best of our knowledge, PPh3-mediated reductive cyclization of nitroarenes is the only method utilized for the synthesis of tribenzo[a,c,g]carbazoles, but rather harsh conditions (typically 180-200 °C) are required for the successful cyclization.11,12 Thus, new methodologies to synthesize this class of carbazoles are desired. We recently reported the synthesis of hydroxyfluoranthenes 5 via a KHMDS-promoted domino reaction of biaryl compounds 1 bearing acyl and naphthylalkenyl moieties (Scheme 1a).13 We clearly showed that oxa-propellanes 3 were the intermediates in this reaction, which were formed via SNAr reaction of (2+2)-cycloadduct 2.14 The thus-formed oxapropellanes 3 underwent rearrangement to form carbopropellanes 4, followed by retro (2+2)-cycloaddition to give the fluoranthenes 5. In contrast, no retro (2+2)-cycloaddition



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of oxapropellanes 3 was observed under the conditions tested. However, the strained structures of heteropropellanes intrigue us as potential precursors of polyaromatic heterocycles if the retro cycloaddition can proceed prior to the rearrangement into 5. We envisaged that a similar (2+2)-cycloaddition and SNAr reaction of imine analogs 6 would give corresponding azapropellanes 7, which would be synthetic intermediates of carbazoles 8 (Scheme 1b). Herein we report a successful development of efficient methods to synthesize tribenzocarbazoles and their analogues. The structural and optical properties of the thus-obtained π-extended carbazoles are also described.

Scheme 1 (a) Our previous report on the synthesis of dibenzofluoranthenes 5 and (b) strategy toward the synthesis of tribenzocarbazoles 8


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Results and Discussion We began our studies by seeking suitable reaction conditions to synthesize azapropellanes 7 (Table 1). When oxime ether 6a was treated with three equivalents of KHMDS in DMF at ambient temperature, the desired azapropellane 7a was not formed (Table 1, entry 1). Alkylimine 6b were also found to be unsuitable (entry 2). In both cases, the resulting reaction mixtures were rather complicated, giving many unidentified side products. In contrast, when N-phenyl enamine 6c was subjected to the reaction conditions, the desired azapropellane 7c was produced in 40% yield (entry 3).15 Higher temperatures benefited this reaction, with 7c obtained in high yield at 110 °C (entries 4 and 5).

Table 1 Optimization of reaction conditions for the synthesis of azapropellanes 7a

a

entry

substrate 6

temp.

time (min)

yield of 7 (%)b

1

6a (R = OMe)

rt

30

0

2

6b (R = PMB)

rt

30

0

3

6c (R = Ph)c

rt

30

40

4

6cc

70 °C

10

61

5

6cc

110 °C

10

85 (82)d

Reaction conditions: 6 (0.050 mmol), KHMDS (3.0 equiv) in DMF (1.0 mL).

b

Yields were determined by 1H NMR using

triphenylmethane as an internal standard. cAn enamine tautomer of 6c was used. dIsolated yields in parentheses; KHMDS = potassium hexamethyldisilazide; DMF = N,N-dimethylformamide; PMB = p-methoxybenzyl.



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Next, we examined the retro (2+2)-cycloaddition to obtain tribenzo[a,c,g]carbazole 8c. When thermal conditions for the retro (2+2)-cycloaddition without any additive were tested, 8c was obtained in 64% yield (Table 2, entry 1). Photo-irradiated conditions16 also promoted the retro cycloaddition, but the yield of 8c was moderate because of side reactions (entry 2). In contrast, when radical-cation-mediated retro cycloaddition17 was examined using (4-BrC6H4)3N+·SbCl6- as an initiator,18 the yield of 8c was increased (entry 3). To our delight, when 7c was treated with a catalytic amount of HCl (5 mol %, 1 M solution in EtOH) in THF at ambient temperature, the carbazole 8c was obtained almost quantitatively (entry 4). Its structure was unambiguously determined by X-ray crystallography (vide infra). The detailed reaction mechanism of the acid-promoted retro reaction is still under investigation.

Table 2 Optimization of reaction conditions for retro (2+2)-cycloaddition of 7c to 8c

a

entry

conditions

yield of 8c (%)b

1a

diglyme, reflux, 24 h

64

2b

hν (Hg), toluene, 20 °C, 2 h

37

3c

(4-BrC6H4)3NSbCl6 (5 mol %), THF, rt, 2 h

78

4d

HCl (5 mol %), THF, rt, 1 h

99f

Conditions: 7c (0.050 mmol) in refluxing diglyme (2 mL). bConditions: 7c (0.050 mmol) in toluene (100 mL) at 20 °C. A

high-pressure mercury vapor lamp was used as the light source. cConditions: 7c (0.050 mmol) and (4-BrC6H4)3N+·SbCl6– (5 mol %) in THF (1 mL) at ambient temperature. dConditions: 7c (0.050 mmol) and HCl (5 mol %) in THF (1 mL) at ambient temperature. eYields were determined by 1H NMR using triphenylmethane as an internal standard. fIsolated yield.

With the appropriate conditions to obtain 7c and 8c in hand, a variety of π-extended carbazoles were synthesized from the corresponding biaryls 6 (Table 3). Note that the azapropellanes 7 obtained in the first step were used after aqueous workup and extraction in the next step without further purification. Carbazole 6 ACS Paragon Plus Environment

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8c was obtained in good yield over two steps. Both electron-donating and withdrawing substituents on the aromatic ring (ArA) of 6 were tolerated, giving carbazoles 8d and 8e, respectively, in good yields (entries 2 and 3). Carbazole 8f, possessing a methoxy substituent on the ArC moiety, was obtained in good yield, albeit elevated temperature was required for the retro (2+2)-cycloaddition (entry 4). Carbazole 8g, bearing a p-bromophenyl group on the nitrogen atom, was also obtained in moderate yield (entry 5). Our method was found to be applicable to the synthesis of tribenzo[a,c,h]carbazole 8h (entry 6). To our delight, further π-extended carbazoles 8i and 8j could be obtained in good yields (entries 7 and 8).

Table 3 Substrate scopea



a

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Reaction conditions for the first step: enamine (0.30 mmol) and KHMDS (3.0 equiv) in DMF (6 mL) at 110 °C, 10 min; second

step: crude azapropellane and HCl (5-10 mol %) in THF. Temperature and time are indicated. Isolated yields are given in parentheses. b5 mol % of HCl was used. c10 mol % of HCl was used. d1,2-dichloroethane was used instead of THF. eEnamine (0.72 g, 1.5 mmol) was used.

The crystallographic structures along with the packing modes of 8c and 8h, the control of which is crucial to the development of light-emitting devices,19 were analyzed by X-ray diffraction. 8c has a characteristic conformation and packing structure in the solid state. The compound consists of a planar naphthalene unit, a twisted [5]helicene moiety with dihedral angle of 21.9°, and an N-phenyl ring located nearly perpendicular to the carbazole moiety (Figures 1a and b). In the packing structure, the mutual π-π interaction between [5]helicene moieties results in dimeric stacking of enantiomeric pairs, with the two enantiomers alternating and aligned longitudinally (Figures 1c, d and Supporting Information). In Figure 1d, the upper and lower molecules show M and P chirality, respectively. The twisted structure results in a rather small overlapping of the aromatic rings. In addition, the distance of π-π stacking is long (ca. 3.8 Å), which indicates the weakness of these face-to-face π-π interactions in the solid state. On the other hand, 8h has a highly planar structure (Figures 1e and f). The overlapping of aromatic rings is greater and the distance of π-π stacking is much shorter (3.6 Å), in clear contrast to 8c.


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Fig. 1 X-ray crystallographic structures of 8c and 8h. Hydrogen atoms are omitted for clarity.

Fig. 2 HOMO and LUMO of carbazole 8c. Calculations were conducted at the B3LYP/6-31G(d) level of theory. 9 ACS Paragon Plus Environment


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To estimate the electronic properties of 8c, DFT calculations were carried out (Figure 2). The geometry was optimized at the B3LYP/6-31G(d) level of theory. The calculated structure was in good agreement with the crystal structure from X-ray diffraction. The HOMO was delocalized over the π-conjugated system and its energy level was –5.03 eV. The LUMO was also spread over the entire molecule, including the phenyl group at the nitrogen atom, and had an energy level of –1.11 eV. The optical properties of tribenzocarbazoles are affected significantly by the fusing of extra benzene rings to the carbazole skeleton, highlighting the importance of the controlled synthesis of tribenzocarbazoles. The UV-vis absorption spectrum of tribenzo[a,c,g]carbazole 8c had local absorption maxima at about 375, 360, and 345 nm (Figure 3). The absorption wavelengths of tribenzo[a,c,h]carbazole 8h were much longer than that of 8c, having local maxima at 409 and 390 nm. Red-shifts of about 40 nm relative to 8c were observed in both the further π-extended carbazoles 8i and 8j, but their spectral patterns differed significantly from each other as a result of the different positions of the added benzene rings. The observed trends for the absorption spectra of 8c, 8h, 8i and 8j could be well explained by theoretical electron transitions obtained by TD-DFT calculations (see Supporting Information).

In addition, 8c, 8h, 8i and 8j showed purple to blue fluorescence with high

quantum yields. The optical properties of carbazoles 8c, 8h, 8i and 8j are summarized in Table 4. The fluorescence spectra of these four carbazoles showed a similar tendency to those observed in the UV-Vis absorption spectra (Figure 4a). In addition, 8c, 8h, 8i and 8j showed violet to light green solid-state fluorescence (Figure 4c), suggesting potential applications in light-emitting devices. The fluorescence of tribenzo[a,c,g]carbazoles 8c, 8i and 8j in the solid state showed similar colors to those in solution (compare Figures 4b and 4c). On the other hand, tribenzo[a,c,h]carbazole 8h in the solid state exhibited a significant


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red-shift and weakening of fluorescence, presumably because of the stronger π-π interactions in the crystals (see Figure 1).

Fig. 3 UV-Vis absorption spectra of carbazoles (2.5 × 10–5 M in dioxane).



8c

8h

8i

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8j

Fig. 4 a) Fluorescence spectra of 8c, 8h, 8i, and 8j (2.5 × 10–6 M in dioxane, λex = 330 nm). b) Photographs of the fluorescence in solution (2.5 × 10–6 M in dioxane) and in the solid state of 8c, 8h, 8i, and 8j under UV irradiation (254 nm).

Table 4 Optical properties in dioxane for 8c, 8h, 8i and 8j 12 ACS Paragon Plus Environment

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a


Compound

λabs, max (nm)a

ε (λabs, max)b

λemc

Φ Fd

8c

375

9560

384, 403

0.50

8h

409

12920

417, 443

0.67

8i

412e

3040

441, 458

0.41

8j

414

16760

432, 454

0.57

Wavelengths of the longest absorption maxima (2.5 × 10–5 M in dioxane). b Molar attenuation coefficient

of λabs, max. c Wavelengths of fluorescence maxima (2.5 × 10–6 M in dioxane, λex = 330 nm). d Fluorescence quantum yields with reference to quinine sulfate in 1 M aq. H2SO4. e The wavelength of absorption edge is indicated.

The relationship of the fluorescent property in solution and solid state of the aforementioned tribenzocarbazoles 8c and 8h can be explained by their three-dimensional structures. The conformation of 8 would be regulated by the three fused aromatic rings (ArA, ArB and ArC). In both cases of 8c and 8h, the ArA group fixes the phenyl ring (ArD) on the nitrogen atom perpendicular to the carbazole framework by the steric hindrance between their ortho hydrogen atoms (Figure 5). Inhibition of the free rotation of the N-ArD bond might reduce the nonradiative quenching of fluorescence of tribenzocarbazoles 8. The fusion manner of the ArC moiety of 8 would determine the planarity of the carbazole skeleton. In case of tribenzo[a,c,g]carbazole 8c, the fused ArB-carbazole-ArC system corresponds to a [5]helicene-like structure and, therefore, the steric hinderance between the ortho hydrogen atoms at the “bay-area” decreases the planarity of the carbazole skeleton. The non-planar structure benefits the solid-state fluorescence by weakening the intermolecular π-π stacking in the crystals. On the other hand, in case of tribenzo[a,c,h]carbazole, the pentacylic framework, ArB-carbazole-ArC, forms a highly planar structure and, therefore, stronger intermolecular π-π interaction was observed in the crystals. As the result, the solid-state fluorescence of 8h was red-shifted by intermolecular contact interactions in crystals. The conformationally 13 ACS Paragon Plus Environment


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rigid planar structure of 8h also makes it possible to have a higher fluorescence quantum yield in solutions compared with the helical carbazoles such as 8c (see Table 4).

Fig. 5 Effects of the aryl groups (ArA, ArB and ArC) to the structures of a) tribenzo[a,c,g]carbazoles and b) tribenzo[a,c,h]carbazoles.

Conclusion In summary, we developed an efficient method to synthesize tribenzocarbazoles by a (2+2)-cycloaddition of biaryls having an enamine moiety giving azapropellane compounds, followed by a retro (2+2)-cycloaddition under acidic conditions. A variety of tribenzocarbazoles possessing different π-conjugation systems, especially unsymmetrically fused ones, were prepared in good yields via this method. The tribenzocarbazoles showed characteristic fluorescence, suggesting potential applications in light-emitting materials. We made clear that the color of fluorescence of tribenzo[a,c,h]carbazole in solution is clearly different from the one in the solid state. In contrast, the fluorescence of tribenzo[a,c,g]carbazole is similar both in solution and the solid state. Strength of the intermolecular π-π interaction in the crystallographic packing structure, which is dependent on the benzo-fusion manner of tribenzocarbazoles, clearly explain rationale for the fluorescence difference.


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Experimental Section General Information. All non-aqueous reactions were carried out in dried glassware under an atmosphere of dry argon. Anhydrous solvents for the reactions were purchased and used without further desiccation. Aniline was purchased and distilled prior to use. All other reagents were purchased and used without further purifications. Analytical TLC was performed on pre-coated silica gel plate (Merck Silica Gel 60 F254). Flash column chromatography was performed on FuJi Silysia BW-200, unless otherwise stated. 1H,

13

C NMR

spectra were recorded on a JEOL JNM-LA 500 at 500 and 125 MHz, respectively. Chemical shifts (δ) and coupling constants (J) are presented in parts per million and hertz, respectively. Tetramethylsilane (δ 0.0 ppm) was used as internal standard for 1H NMR. Residual CDCl3 (δ 77.0 ppm) was used as internal standard for 13C NMR. Multiplicities are indicated as s (singlet), d (doublet), t (triplet), m (multiplet), and br (broad). High-resolution mass spectra were measured on a Shimadzu LCMS-IT-TOF fitted with an ESI or JEOL MS700 spectrometer (FAB). IR spectra were recorded on a Shimadzu IRAffinity-1, and the wave numbers of maximum absorption peaks are reported in cm−1. Melting points were determined on YANACO micro melting point apparatus. X-Ray single crystal diffraction analyses were performed on a Rigaku XtaLAB P200 apparatus. UV-Vis absorption spectra were recorded on a Shimazu UV-2600. Fluorescence spectra were recorded on a JASCO FP-8600 and quantum yields were determined by using quinine sulfate in 1M aq. H2SO4 as reference (ΦF = 0.54). Preparation of Biaryl Ketones (1) Biaryl ketones were prepared according to previously reported methods.12 1-{2'-[1-(2-Methoxynaphthalen-1-yl)vinyl]-(1,1'-biphenyl)-2-yl}-2-methylpropan-1-one (1c). 15 ACS Paragon Plus Environment


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White solids: mp. 115–116 °C 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.74–0.98 (br m, 6H), 2.67 (br s, 1H), 3.63 (s, 3H), 5.34 (s, 1H), 5.62 (s, 1H), 6.92–6.98 (m, 1H), 6.99–7.13 (br m, 3H), 7.13–7.41 (br m, 7H), 7.59–7.74 (m, 2H), 7.95 (d, J = 8.0 Hz, 1H) ppm;

13

C NMR (125 MHz, CDCl3, 50 °C): δ 17.9, 19.5, 38.9,

56.2, 113.8, 123.1, 123.3, 125.5, 126.1, 126.3, 126.6, 127.4, 127.6, 127.9, 129.1, 129.2, 130.2, 130.8, 131.2, 133.3, 138.7, 140.1, 140.4, 141.4, 142.8, 153.7, 210.4 ppm (two peaks missing); IR (neat): 3012, 2970, 1658 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C29H27O2, 407.2006; found, 407.2002. 1-{4-Methoxy-2'-[1-(2-methoxynaphthalen-1-yl)vinyl]-(1,1'-biphenyl)-2-yl}-2-methylpropan-1-one (1d). Pale yellow paste; 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.69–1.03 (br m, 6H), 2.47–2.80 (br s, 1H), 3.63 (s, 1H), 3.70 (s, 3H), 5.36 (s, 1H), 5.64 (s, 1H), 6.39–6.88 (br m, 2H), 6.95 (d, J = 7.2 Hz, 1H), 6.99–7.47 (br m, 7H), 7.61–7.76 (m, 2H), 7.94 (d, J = 8.0 Hz, 1H) ppm;

13

C NMR (125 MHz, CDCl3, 50 °C): δ 18.0, 19.5,

39.0, 55.2, 56.2, 112.9, 113.9, 115.5, 122.8, 123.3, 125.6, 126.1, 126.4, 126.6, 127.3, 127.6, 129.0, 129.3, 130.3, 131.0, 132.3, 132.7, 133.2, 138.4, 141.1, 141.9, 143.1, 153.7, 158.1, 210.4 ppm; IR (neat): 3012, 2966, 1685 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C30H29O3, 437.2111; found, 437.2123. 1-{4-Chloro-2'-[1-(2-methoxynaphthalen-1-yl)vinyl]-(1,1'-biphenyl)-2-yl}-2-methylpropan-1-one (1e). White solids: mp. 83–85 °C 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.66–1.03 (br m, 6H), 2.32–2.79 (br m, 1H), 3.63 (s, 3H), 5.38 (s, 1H), 5.65 (s, 1H), 6.67–7.52 (br m, 10H), 7.58–7.78 (br m, 2H), 7.88 (d, J = 7.5 Hz, 1H) ppm;

13

C NMR (125 MHz, CDCl3, 50 °C): δ 17.9, 19.3, 38.9, 56.1, 113.6, 123.2, 123.4, 125.3,

125.9, 126.2, 126.8, 127.68, 127.72, 127.8, 129.2, 130.5, 132.5, 133.1, 137.5, 138.6, 141.3, 142.0, 142.8, 153.6, 208.8 ppm (four signals missing); IR (neat): 3012, 2970, 1689 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C29H26ClO2, 441.1616; found, 441.1626. 1-{2'-[1-(2,7-Dimethoxynaphthalen-1-yl)vinyl]-(1,1'-biphenyl)-2-yl}-2-methylpropan-1-one (1f).


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The spectroscopic data were in good agreement with those reported.12 1-{2'-[1-(3-Methoxynaphthalen-2-yl)vinyl]-(1,1'-biphenyl)-2-yl}-2-methylpropan-1-one (1h). Pale yellow paste: 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.50–0.83 (m, 6H), 2.29–2.40 (m, 1H), 3.64 (s, 3H), 5.39 (d, J = 1.7 Hz, 1H), 5.49 (d, J = 1.7 Hz, 1H), 6.87 (s, 1H), 7.03 (d, J = 7.7 Hz, 1H), 7.07–7.14 (m, 2H), 7.18–7.24 (m, 3H), 7.26–7.29 (m, 2H), 7.30–7.36 (m, 2H), 7.46 (d, J = 7.7 Hz, 1H), 7.51 (d, J = 8.0 Hz, 1H), 7.58 (d, J = 8.0 Hz, 1H) ppm;

13

C NMR (125 MHz, CDCl3, 50 °C): δ 18.1, 18.89, 18.93, 38.7, 54.9,

105.1, 120.6, 123.3, 125.9, 126.5, 126.9, 127.3, 127.4, 127.7, 128.3, 129.0, 129.7, 130.0, 130.4, 131.1, 132.3, 133.8, 138.5, 139.4, 140.0, 141.4, 146.9, 155.3, 210.2 ppm (four signals missing); IR (neat): 3055, 2970, 2870, 1685 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C29H27O2, 407.2006; found, 407.2003. 1-(3-{2-[1-(2-Methoxynaphthalen-1-yl)vinyl]phenyl}naphthalen-2-yl)-2-methylpropan-1-one (1i). White solids: mp. 156–157 °C; 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.72–1.04 (m, 6H), 2.61–2.96 (m, 1H), 3.62 (s, 3H), 5.33 (s, 1H), 5.71 (s, 1H), 6.93–7.13 (m, 4H), 7.16–7.32 (m, 2H), 7.33–7.66 (m, 7H), 7.71 (d, J = 7.2 Hz, 1H), 7.76–7.89 (m, 2H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 18.1, 19.7, 38.7, 56.2, 113.6, 123.0, 123.1, 125.3, 125.8, 126.1, 126.6, 127.18, 128.23, 127.4, 127.8, 128.2, 128.3, 129.0, 130.7, 131.4, 133.0, 133.5, 136.9, 138.2, 139.1, 141.9, 143.4, 153.7, 209.1 ppm (four signals missing); IR (neat): 3055, 2966, 1685 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C33H29O2, 457.2162; found, 457.2174. 1-{2'-[1-(2-Methoxyanthracen-1-yl)vinyl]-(1,1'-biphenyl)-2-yl}-2-methylpropan-1-one (1j). Pale yellow solids: mp. 178–180 °C 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.73–0.96 (br m, 6H), 2.50–2.77 (br s, 1H), 3.62 (s, 3H), 5.47 (s, 1H), 5.75 (s, 1H), 6.57–7.29 (br m, 8H), 7.32–7.48 (br m, 3H), 7.79–7.97 (m, 3H), 8.21 (s, 1H), 8.50 (s, 1H) ppm;

13

C NMR (125 MHz, CDCl3, 50 °C): δ 18.3, 19.3, 39.0, 56.5, 115.6,

123.1, 124.2, 124.6, 125.09, 125.14, 125.9, 126.1, 126.7, 127.5, 127.7, 127.8, 128.3, 128.6, 129.1, 129.7,



Page 18 of 32

130.1, 130.47, 130.54, 131.0, 131.4, 132.0, 138.9, 140.0, 140.2, 142.3, 143.4, 152.7, 210.4 ppm; IR (neat): 3012, 2970, 2931, 1681 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C33H29O2, 457.2162; found, 457.2164. 1-(2'-{1-[2-(Methoxymethoxy)naphthalen-1-yl]vinyl}-(1,1'-biphenyl)-2-yl)-2-methylpropan-1-one (1a). The spectroscopic data were in good agreement with those reported.12 Preparation of 6a. To a stirred solution of 1a (776 mg, 1.78 mmol) and MeONH3Cl (743 mg, 8.90 mmol) in dry nBuOH (9.0 mL) was added pyridine (0.71 mL, 8.9 mmol) and refluxed for 15 hours. After cooling to room temperature, the reaction mixture was quenched with 1N HCl. Phases were separated, and the aqueous layer was extracted three times with EtOAc. The combined organic layer was washed with brine, dried over MgSO4 and concentrated. The deprotection of MOM group was observed. To a stirred solution of the crude product above and K2CO3 (1.19 g, 8.60 mmol) in dry acetone (10 mL) was added Me2SO4 (0.82 mL, 8.6 mmol) and heated for 12 hours at 50 °C. After cooling to room temperature, the reaction mixture was quenched with 1N HCl and diluted with EtOAc. Phases were separated, and the aqueous layer was extracted three times with EtOAc. The combined organic layer was washed with brine, dried over MgSO4 and concentrated. The residue was purified by silica gel column chromatography (hexanes/EtOAc) to give 6a (434 mg, 58%) as pale yellow paste: 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.86 (br s, 3H), 0.95 (br s, 3H), 2.65 (br s, 1H), 3.60 (s, 3H), 3.78 (s, 3H), 5.28 (s, 1H), 5.58 (s, 1H), 6.89–7.36 (br m, 11H), 7.59–7.79 (m, 2H), 7.94 (d, J = 8.0 Hz, 1H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 18.6, 32.6, 56.3, 62.4, 114.0, 122.9, 123.3, 125.5, 126.1, 126.15, 126.23, 127.0, 127.1, 127.2, 127.5, 128.9, 129.2, 129.3, 130.0, 131.1, 131.8, 133.5, 137.0, 139.2, 140.8, 141.1, 142.7, 153.7, 164.5 ppm (one signal missing); IR


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(neat): 3055, 2962, 2873, 1739 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C30H30NO2, 436.2271; found, 436.2279. Preparation of 6b. To a stirred solution of 1c (203 mg, 0.50 mmol) and 4-methoxybenzylamine (0.32 mL, 2.5 mmol) in toluene (5.0 mL) was added TiCl4 (1M in toluene, 0.25 mL, 0.25 mmol) and refluxed for 11 hours. After cooling to room temperature, the reaction mixture was filtered through a pad of Celite®, washed with brine, and dried over MgSO4. After evaporation, the residue was purified by silica gel column chromatography (hexanes/EtOAc/Et3N) to give the title compound (158 mg, 60%) as pale yellow paste: 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.60–1.11 (br m, 6H), 2.26 (s, 1H), 3.67 (s, 3H), 3.80 (s, 3H), 4.51 (br s, 2H), 5.33 (s, 1H), 5.45 (s, 1H), 6.58–7.24 (br m, 11H), 7.26–7.64 (br m, 4H), 7.67–7.82 (m, 2H), 7.93 (br s, 1H) ppm;

13

C

NMR (125 MHz, CDCl3, 50 °C): 18.9, 21.2, 37.1, 55.3, 55.9, 56.3, 113.8, 113.9, 123.0, 123.4, 125.3, 125.9, 126.4, 126.6, 126.7, 127.2, 127.4, 127.8, 128.3, 129.2, 129.4, 130.4, 130.7, 131.9, 133.3, 133.6, 137.8, 138.3, 138.9, 140.6, 142.9, 153.8, 158.3, 178.2 ppm (one signal missing); IR (neat): 3059, 2958, 2835, 1647 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C37H36NO2, 526.2741; found, 526.2755. Preparation of Enamines 6c-j. General Procedure: To a stirred solution of biaryl ketone 1 (1.0 equiv) and aniline (5.0 equiv) in dry benzene (0.1 M) was added TiCl4 (1M in toluene, 1.5 equiv) and refluxed for 12 hours. After cooling to room temperature, the reaction mixture was filtered through a pad of Celite®, washed with brine, and dried over MgSO4. After evaporation, the residue was purified by silica gel column chromatography (hexanes/EtOAc/Et3N) to give the desired enamines. 6c: The general procedure using 1c (5.0 mmol scale) gave the title compound (1.74 g, 72%) as white solids:



Page 20 of 32

mp. 137–139 °C; 1H NMR (500 MHz, CDCl3, 50 °C): δ 1.56 (s, 3H), 1.63 (s, 3H), 5.12 (s, 1H), 5.15 (s, 1H), 5.27 (br s, 1H), 6.33 (d, J = 7.7 Hz, 2H), 6.40–6.52 (m, 1H), 6.60 (t, J = 7.0 Hz, 1H), 6.71 (t, J = 7.5 Hz, 1H), 6.90–7.08 (m, 5H), 7.11–7.19 (m, 3H), 7.20–7.25 (m, 3H), 7.61–7.76 (m, 3H); 13C NMR (125 MHz, CDCl3, 50 °C): δ 20.3, 21.3, 56.1, 113.5, 114.6, 117.2, 123.2, 125.5, 125.8, 126.09, 126.13, 126.4, 126.5, 127.2, 127.7, 128.4, 128.7, 129.2, 129.7, 129.9, 130.4, 130.6, 132.2, 133.5, 139.2, 139.7, 140.6, 141.2, 142.2, 145.6, 153.4 ppm (two signals missing); IR (neat): 3363, 3051, 2904, 2839 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C35H32NO, 482.2479; found, 482.2475. 6d: The general procedure using 1d (4.9 mmol scale) gave the title compound (948 mg, 38%) as pale yellow paste; 1H NMR (500 MHz, CDCl3, 50 °C): δ 1.55 (s, 3H), 1.64 (s, 3H), 3.55 (s, 3H), 3.71 (s, 3H), 5.13 (s, 1H), 5.19 (s, 1H) 5.27 (br s, 1H), 6.23 (d, J = 7.7 Hz, 1H), 6.27–6.42 (m, 3H), 6.60 (t, J = 7.3 Hz, 1H), 6.78 (d, J = 1.4 Hz, 1H), 6.89–6.98 (m, 1H), 6.98–7.07 (m, 3H), 7.08–7.30 (m, 5H), 7.56–7.76 (m, 3H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 20.3, 21.3, 55.2, 56.1, 111.6, 113.4, 114.7, 116.0, 117.2, 123.1, 123.2, 125.5, 126.1, 126.4, 126.7, 127.0, 127.7, 128.4, 128.7, 129.2, 129.7, 130.7, 130.9, 132.1, 133.4, 133.6, 139.4, 140.3, 141.1, 142.5, 145.6, 153.3, 157.6 ppm (one signal missing); IR (neat): 3363, 3051, 3005 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C36H34NO2, 512.2584; found, 512.2584. 6e: The general procedure using 1e (5.0 mmol scale) gave the title compound (1.49 g, 58%) as white solids: mp. 133–135 °C; 1H NMR (500 MHz, CDCl3, 50 °C): δ 1.51 (s, 3H), 1.58 (s, 3H), 3.53 (s, 3H), 5.20 (s, 1H), 5.26 (s, 1H), 5.43 (br s, 1H), 6.12 (d, J = 7.2 Hz, 1H), 6.30 (d, J = 8.0 Hz, 2H), 6.53 (d, J = 8.0 Hz, 1H), 6.62 (t, J = 7.3 Hz, 1H), 6.89 (d, J = 6.9 Hz, 1H), 6.96 (d, J = 8.9 Hz, 1H), 7.04 (t, J = 7.7 Hz, 2H), 7.11–7.31 (m, 6H), 7.58 (d, J = 8.3 Hz, 1H), 7.64–7.74 (m, 2H) ppm;

13

C NMR (125 MHz, CDCl3, 50 °C): δ 20.4, 21.3,

55.9, 113.1, 114.7, 117.5, 123.3, 123.4, 125.3, 125.9, 126.2, 126.5, 127.5, 127.7, 128.5, 128.9, 129.1, 129.8,


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130.1, 131.1, 131.5, 133.3, 138.5, 139.5, 141.0, 141.3, 142.5, 145.2, 153.2 ppm (four signals missing); IR (neat): 3363, 3051, 3008, 2904 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C35H31ClNO, 516.2089; found, 516.2098. 6f: The general procedure using 1f (10.0 mmol scale) gave the title compound (2.73 g, 53%) as white solids: mp. 130–131 °C; NMR (500 MHz, CDCl3, 50 °C): δ 1.48 (s, 3H), 1.53 (s, 3H), 3.43 (s, 3H), 3.55 (s, 3H), 5.26 (s, 1H), 5.31 (s, 1H), 5.70 (br s, 1H), 6.11 (br s, 1H), 6.35 (d, J = 7.7 Hz, 2H), 6.56 (t, J = 7.0 Hz, 1H), 6.61 (t, J = 7.3 Hz, 1H), 6.68 (br s, 1H),. 6.85–6.91 (m, 2H), 6.93 (d, J = 7.5 Hz, 1H), 7.03 (t, J = 7.7 Hz, 2H), 7.11–7.22 (m, 3H), 7.35 (d, J = 6.6 Hz, 1H), 7.51 (d, J = 8.9 Hz, 1H), 7.56 (d, J = 9.5 Hz, 1H) ppm;

13

C

NMR (125 MHz, CDCl3, 50 °C): δ 20.4, 21.2, 54.8, 55.6, 103.6, 110.1, 114.6, 116.0, 117.0, 120.7, 123.2, 124.3, 124.5, 125.7, 125.8, 126.4, 127.0, 128.2, 129.2, 129.3, 129.6, 129.8, 130.3, 131.8, 134.2, 139.2, 139.6, 140.7, 141.4, 142.9, 145.5, 153.7, 157.6 ppm (one signal missing); IR (neat): 3363, 3008, 2904 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C36H34NO2, 512.2584; found, 512.2585. 6g: The general procedure using 1c (3.0 mmol scale) and 4-bromoaniline instead of aniline gave the title compound (850 mg, 51%) as a mixture of imine and enamine (0.4 : 0.6): 1H NMR (500 MHz, CDCl3, 50 °C): δ 0.60–1.26 (br m, 2.4H), 1.51 (s, 1.8H), 1.60 (s, 1.8H), 2.30–2.84 (br s, 0.4H), 3.55 (s, 1.8H), 3.66 (s, 1.2H), 4.86–5.65 (br m, 2.6H), 6.15 (d, J = 8.6 Hz 1.2H), 6.25–6.86 (br m, 2H), 6.87–7.06 (br m, 2.6H), 7.06–7.41 (br m, 8.6H), 7.43–7.84 (br m, 3H), 7.92 (d, J = 7.2 Hz, 0.4H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 19.5, 20.4, 21.3, 21.6, 37.7, 56.0, 56.2, 108.7, 113.2, 113.9, 115.8, 116.3, 122.4, 123.0, 123.2, 123.4, 125.3, 125.7, 125.8, 126.1, 126.5, 127.3, 127.4, 127.7, 127.8, 128.7, 129.1, 129.3, 129.6, 129.8, 130.3, 131.0, 131.3, 132.0, 132.2, 133.3, 133.6, 137.3, 138.0, 138.6, 139.1, 139.5, 140.5, 141.0, 141.1, 142.4, 144.4, 149.8, 153.1, 153.7, 178.3 ppm (12 signals missing); IR (neat): 3352, 3055, 3008, 2931, 2850, 1620 cm-1; HRMS–ESI



Page 22 of 32

(m/z): [M+H]+ calcd for C35H31NOBr, 560.1584; found, 560.1582. 6h: The general procedure using 1h (3.0 mmol scale) gave the title compound (667 mg, 46%) as white solids: mp. 119–120 °C; NMR (500 MHz, CDCl3, 50 °C): δ 1.53 (s, 6H), 3.59 (s, 3H), 5.12 (br s, 1H), 5.24 (d, J = 1.7 Hz, 1H), 5.44 (d, J = 1.7 Hz, 1H), 6.37 (d, J = 7.7 Hz, 2H), 6.57 (t, J = 7.3 Hz, 1H), 6.63–6.71 (m, 2H), 6.87 (s, 1H), 6.97–7.02 (m, 1H), 7.02–7.10 (m, 3H), 7.15 (s, 1H), 7.19–7.29 (m, 4H), 7.29–7.37 (m, 2H), 7.50 (d, J = 8.3 Hz, 1H), 7.60 (d, J = 8.3 Hz, 1H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 20.2, 21.5, 55.2, 105.6, 113.9, 116.9, 120.7, 123.6, 126.05, 126.12, 126.3, 126.7, 126.8, 127.6, 128.5, 128.7, 129.6, 129.9, 130.35, 130.40, 130.8, 131.4, 133.2, 133.8, 139.3, 140.5, 140.8, 141.8, 145.7, 146.2, 155.3 ppm; IR (neat): 3375, 3051, 3012, 2908 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C35H32NO, 482.2479; found, 482.2480. 6i: The general procedure using 1i (5.0 mmol scale) gave the title compound (2.28 g, 59%) as pale yellow solids: mp. 168–169 °C; NMR (500 MHz, CDCl3, 50 °C): δ 1.58 (s, 3H), 1.64 (s, 3H), 3.48 (s, 3H), 5.10 (s, 1H), 5.20 (s, 1H), 5.41 (br s, 1H), 6.32 (d, J = 8.0 Hz, 2H), 6.52–6.85 (br m, 3H), 6.92–7.00 (m, 1H), 7.02 (t, J = 7.7 Hz, 2H), 7.16–7.23 (m, 5H), 7.23–7.30 (m, 2H), 7.35 (t, J = 7.5 Hz, 2H), 7.57–7.76 (m, 4H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 20.6, 21.4, 55.9, 112.8, 114.9, 117.3, 123.1, 123.3, 125.2, 125.4, 125.5, 126.1, 126.3, 127.1, 127.3, 127.6, 127.7, 128.3, 128.8, 129.0, 129.1, 129.8, 130.6, 131.91, 131.94, 132.2, 133.2, 137.7, 138.9, 139.5, 140.8, 142.5, 145.3, 153.0 ppm (three signals missing); IR (neat): 3363, 3051, 2978 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C39H34NO, 532.2635; found, 532.2646. 6j: The general procedure using 1j (4.0 mmol scale) gave the title compound (685 mg, 32%) as pale yellow solids: mp. 119–120 °C; NMR (500 MHz, CDCl3, 50 °C): δ 1.57 (s, 3H), 1.61 (s, 3H), 3.59 (s, 3H), 5.19– 5.28 (m, 2H), 5.33 (br s, 1H), 6.33–6.45 (m, 2H), 6.64 (t, J = 7.0 Hz 2H), 6.95 (d, J = 7.5 Hz, 2H), 7.06–7.12


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(m, 3H), 7.13–7.23 (m, 3H), 7.28–7.39 (m, 3H), 7.65 (br s, 1H), 7.81–7.94 (m, 2H), 8.20 (s, 1H), 8.29 (s, 1H) ppm; 13C NMR (125 MHz, CDCl3, 50 °C): δ 20.3, 21.3, 56.4, 114.6, 115.2, 117.2, 123.4, 123.9, 124.6, 125.1, 125.2, 125.8, 126.0, 126.1, 126.5, 127.2, 127.8, 128.4, 128.5, 128.6, 129.4, 129.85, 129.90, 130.0, 130.3, 130.5, 131.9, 132.0, 132.1, 139.3, 139.7, 140.97, 141.03, 142.6, 145.8, 152.4 ppm (one signal missing); IR (neat): 3367, 3051, 3012, 2978 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C39H34NO, 532.2635; found, 532.2642. Synthesis of Azapropellane 7c. To a stirred solution of enamines (0.30 mmol) in dry DMF (6.0 mL), KHMDS (1M in THF, 0.90 mL, 0.90 mmol) was added quickly at 110 °C. After stirring for 10 min, the reaction mixture was cooled to 0 °C and water was added. The aqueous layer was extracted three times with Et2O and the combined organic layer was washed twice with water followed by brine, dried over MgSO4, and concentrated. The resulting solids were washed with hexanes followed by Et2O to give the title compound as pale yellow solids: mp. 198–199 °C; 1H NMR (500 MHz, Acetone-d6): δ 0.73 (s, 3H), 1.36 (s, 3H), 2.22 (d, J = 11.2 Hz, 1H), 3.07 (d, J = 11.2 Hz, 1H), 6.36 (br s, 1H), 6.48 (d, J = 8.6 Hz, 1H), 6.78 (d, J = 7.7 Hz, 1H), 6.98 (t, J = 7.2 Hz, 1H), 7.05–7.18 (m, 2H), 7.23 (t, J = 7.9 Hz, 2H), 7.25–7.34 (m, 2H), 7.43–7.65 (m, 4H), 7.79 (d, J = 8.0 Hz, 1H), 7.98 (d, J = 8.0 Hz, 1H), 8.08 (d, J = 7.7 Hz, 1H), 8.15 (d, J = 8.0 Hz, 1H), 8.25 (d, J = 8.6 Hz, 1H) ppm; 13C NMR spectrum could not be measured due to the low stability; IR (neat): 3059, 3008, 2927 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C34H28N, 450.2216; found, 450.2210. Synthesis of Carbazoles 8c-j. General Procedure: To a stirred solution of enamines (0.30 mmol) in dry DMF (6.0 mL), KHMDS (1M in THF, 0.90 mL, 0.90 mmol) was added quickly at 110 °C. After stirring for 10 min, the reaction mixture was



Page 24 of 32

cooled to 0 °C and water was added. The aqueous layer was extracted three times with Et2O and the combined organic layer was washed twice with water followed by brine, dried over MgSO4, and concentrated. To the resulting solids were added dry THF (6.0 mL) and HCl (1M in EtOH, 5–10 mol %), and the resulting solution was stirred at indicated temperature. When the completion of the reaction was confirmed by 1H NMR, sat. aq. NaHCO3 was added. The aqueous layer was extracted three times with CHCl3, and the combined organic layer was dried over MgSO4 and concentrated. The residue was purified by silica gel column chromatography (hexanes/EtOAc) to give the desired carbazoles. 8c: The general procedure (1.5 mmol scale) using 6c and 5 mol % of HCl at room temperature gave the title compound (466 mg, 79%) as pale yellow prisms: mp. 241–243 °C; 1H NMR (500 MHz, CDCl3): δ 7.25–7.29 (m, 1H), 7.32 (d, J = 8.9 Hz, 1H), 7.42 (d, J = 8.3 Hz, 1H), 7.48–7.59 (m, 4H), 7.60–7.73 (m, 6H), 7.77 (d, J = 8.9 Hz, 1H), 8.01 (d, J = 8.0 Hz, 1H), 8.72–8.84 (m, 2H), 9.12 (d, J = 8.3 Hz, 1H), 9.18 (d, J = 8.0 Hz, 1H) ppm;

13

C NMR (125 MHz, CDCl3): δ 112.0, 116.8, 117.3, 122.6, 123.4, 123.6, 123.77, 123.82, 124.4,

125.2, 125.3, 125.4, 125.6, 126.0, 126.1, 126.3, 127.8, 128.6, 128.98, 129.01, 129.1, 130.3, 130.4, 130.7, 133.5, 139.3, 139.7 ppm (one signal missing); IR (neat): 2924, 2850 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C30H20N, 394.1590; found, 394.1591. 8d: The general procedure using 6d and 5 mol % of HCl at room temperature gave the title compound (116 mg, 91%) as pale yellow solids: mp. 238–239 °C; 1H NMR (500 MHz, CDCl3): δ 3.40 (s, 3H), 6.89 (d, J = 2.6 Hz, 1H), 7.14 (dd, J = 9.2, 2.6 Hz, 1H), 7.33 (d J = 8.6 Hz, 1H), 7.53 (t, J = 7.5 Hz, 1H), 7.58–7.68 (m, 6H), 7.68–7.74 (m, 2H), 7.78 (d, J = 8.9 Hz, 1H), 8.02 (d, J = 8.0 Hz, 1H), 8.67 (t, J = 9.0 Hz, 2H), 9.08– 9.22 (m, 2H) ppm;

13

C NMR (125 MHz, CDCl3): δ 54.5, 103.7, 111.9, 115.6, 117.3, 117.4, 123.2, 123.6,

124.4, 124.5, 124.6, 125.0, 125.2, 125.3, 125.4, 125.6, 126.3, 127.9, 128.6, 129.0, 129.1, 129.5, 130.2, 130.4,


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133.1, 139.3, 139.8, 157.6 ppm (one signal missing); IR (neat): 3016, 2920 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C31H22NO, 424.1696; found, 424.1699. 8e: The general procedure using 6e and 10 mol % of HCl at 60 °C gave the title compound (106 mg, 83%) as pale yellow solids: mp. >250 °C; 1H NMR (500 MHz, CDCl3): δ 7.30 (d, J = 2.0 Hz, 1H), 7.34 (d, J = 8.9 Hz, 1H), 7.47 (dd, J = 8.7, 1.9 Hz, 1H), 7.50–7.60 (m, 3H), 7.61–7.69 (m, 2H), 7.69–7.76 (m, 4H), 7.80 (d, J = 8.9 Hz, 1H), 8.02 (d, J = 7.7 Hz, 1H), 8.70 (t, J = 8.6 Hz), 9.10 (d, J = 8.3 Hz, 1H), 9.18 (d, J = 8.3 Hz, 1H) ppm;

13

C NMR (125 MHz, CDCl3): δ 112.0, 117.1, 117.7, 122.1, 123.7, 123.8, 124.3, 124.7, 125.2, 125.3,

125.35, 125.44, 125.7, 126.2, 126.8, 127.2, 128.6, 128.9, 129.0, 129.1, 129.4, 130.4, 131.9, 132.2, 139.1, 139.5 ppm (two signals missing); IR (neat): 3032, 2920 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C30H18ClN 428.1201; found, 428.1201. 8f: The general procedure using 6f and 10 mol % of HCl at 60 °C gave the title compound (106 mg, 83%) as pale yellow solids: mp. 238–239 °C; 1H NMR (500 MHz, CDCl3): δ 4.01 (s, 3H), 7.15–7.22 (m, 2H), 7.27– 7.32 (m, 1H), 7.43 (d, J = 8.3 Hz, 1H), 7.50–7.60 (m, 3H), 7.61–7.76 (m, 6H), 7.91 (d, J = 8.9 Hz, 1H), 8.43 (d, J = 1.7 Hz, 1H), 8.79 (d, J = 8.3 Hz, 2H), 9.18 (d, J = 8.3 Hz, 1H) ppm; 13C NMR (125 MHz, CDCl3): δ 55.4, 105.6, 109.5, 115.4, 116.7, 116.9, 122.6, 123.4, 123.7, 123.9, 124.3, 125.2, 125.3, 125.5, 125.9, 126.0, 126.1, 127.8, 128.8, 129.0, 129.1, 129.6, 130.1, 130.4, 130.6, 133.4, 139.8, 139.9, 157.3 ppm; IR (neat): 3012, 2924 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C31H22NO, 424.1696; found, 424.1708. 8g: The general procedure using 6g and 10 mol % of HCl at 80 °C in 1,2-DCE gave the title compound (47.6 mg, 34%) as white solids: mp. >250 °C; 1H NMR (500 MHz, CDCl3): δ 7.29–7.38 (m, 2H), 7.41–7.49 (m, 3H), 7.51–7.60 (m, 2H), 7.62–7.69 (m, 2H), 7.71 (t, J = 7.5 Hz, 1H), 7.77–7.88 (m, 3H), 8.02 (d, J = 8.0 Hz, 1H), 8.73–8.85 (m, 2H), 9.10 (d, J = 8.3 Hz, 1H), 9.16 (d, J = 8.0 Hz, 1H) ppm;


13

C NMR (125 MHz,


Page 26 of 32

CDCl3): δ 111.6, 117.2, 117.6, 122.4, 123.0, 123.1, 123.79, 123.82, 123.9, 124.6, 125.3, 125.4, 125.5, 125.6, 126.1, 126.3, 126.5, 127.8, 128.5, 128.8, 129.0, 130.5, 130.65, 130.69, 133.2, 133.5, 138.8, 139.1 ppm; IR (neat): 3066, 3016 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C30H19BrN, 472.0696; found, 472.0688. 8h: The general procedure using 6h and 10 mol % of HCl at 80 °C in 1,2-DCE gave the title compound (40.6 mg, 34%) as pale yellow prisms: mp. >250 °C; 1H NMR (500 MHz, CDCl3): δ 7.29–7.35 (m, 1H), 7.40–7.50 (m, 2H), 7.55 (dd, J = 8.3, 0.9 Hz, 1H), 7.57–7.64 (m, 4H), 7.65–7.78 (m, 4H), 7.83–7.95 (m, 2H), 8.16–8.23 (m, 1H), 8.81–8.90 (m, 2H), 9.08–9.18 (m, 2H) ppm;

13

C NMR (125 MHz, CDCl3): δ 106.2, 113.7, 120.0,

122.8, 123.3, 123.6, 123.7, 123.76, 123.83, 124.0, 124.8, 125.7, 125.9, 126.3, 127.15, 127.24, 127.6, 128.6, 128.8, 129.2, 129.4, 129.8, 130.3, 131.1, 131.5, 137.8, 140.6, 142.5 ppm; IR (neat): 3082, 3051, 3012 cm-1; HRMS–ESI (m/z): [M]+ calcd for C30H19N, 393.1512; found, 393.1519. 8i: The general procedure using 6i and 5 mol % of HCl at room temparature gave the title compound (124 mg, 93%) as pale yellow solids: mp. >250 °C; 1H NMR (500 MHz, CDCl3): δ 7.33–7.43 (m, 2H), 7.43–7.57 (m, 3H), 7.69–7.83 (m, 6H), 8.02 (d, J = 8.3 Hz, 1H), 8.89 (d, J = 8.0 Hz, 1H), 9.11 (d, J = 8.3 Hz, 2H), 9.22 (s, 1H) ppm; 13C NMR (125 MHz, CDCl3): δ 112.0, 116.6, 117.7, 121.3, 122.45, 122.52, 123.7, 124.3, 124.7, 125.1, 125.4, 125.6, 125.66, 125.71, 126.1, 126.5, 128.0, 128.1, 128.4, 128.5, 129.0, 129.16, 129.23, 129.6, 130.3, 130.5, 130.7, 131.2, 133.2, 139.1, 139.7 ppm (one signal missing); IR (neat): 3051, 2920 cm-1; HRMS–ESI (m/z): [M+H]+ calcd for C34H22N, 444.1747; found, 444.1746. 8j: The general procedure using 6j and 10 mol % of HCl at 80 °C in 1,2-DCE gave the title compound (101 mg, 76%) as yellow solids: mp. >250 °C; 1H NMR (500 MHz, CDCl3): δ 7.20–7.33 (m, 2H), 7.40 (d, J = 8.3 Hz, 1H), 7.46–7.60 (m, 5H), 7.62–7.77 (m, 5H), 7.85 (d, J = 8.9 Hz, 1H), 8.06 (d, J = 8.0 Hz, 1H), 8.11 (d, J = 8.0 Hz, 1H), 8.53 (s, 1H), 8.72–8.85 (m, 2H), 9.37 (d, J = 8.0 Hz, 1H), 9.66 (s, 1H) ppm; 13C NMR (125


Page 27 of 32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


MHz, CDCl3): δ 113.3, 116.0, 117.6, 122.4, 123.2, 123.5, 123.8, 123.9, 124.66, 124.73, 125.1, 125.3, 125.6, 125.9, 126.2, 126.9, 127.2, 127.9, 128.0, 128.1, 129.0, 129.1, 129.2, 130.0, 130.1, 130.3, 130.5, 131.1, 132.7, 138.5, 139.6 ppm; IR (neat): 3051, 2920 cm-1; HRMS–FAB (m/z): [M+H]+ calcd for C34H22N, 444.1747; found, 444.1754.

Supporting Information. Crystallographic information for 8c and 8h, UV-vis and fluorescent spectra for 8, computational study for 8c, 8h, 8i, and 8j, and copies of 1H and 13C NMR spectra for all new compounds. This material is available free of charge via the Internet at http://pubs.acs.org. Acknowledgement. We thank JSPS KAKENHI Grant Number 16H05073, MEXT KAKENHI Grant Number JP16H01147 in Middle Molecular Strategy, and AMED Platform for Supporting Drug Discovery and Life Science Research. This work was supported by the Sasakawa Scientific Research Grant from The Japan Science Society.

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Cycloaddition of Azapropellanes

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