Bulletin of the Chemical Society of Japan

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1 Supporting Information Bulletin of the Chemical Society of Japan 1,4-Selective Diels Alder Reaction of 9,10-Diethynylanthracene with 3,6-Difluorobenzyne Yoshitaka Tsuchido, 1 Tomohito Ide, 2 Yuji Suzaki, 1 and Kohtaro Osakada* 1 1 Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa Corporate Research & Development Center, Toshiba Corporation, 1 Komukai-Toshiba-cho, Saiwai-ku, Kawasaki, Kanagawa (Received January 13, 2015; kosakada@res.titech.ac.jp) Copyright The Chemical Society of Japan

2 Contents S1. Materials and methods S2. Synthesis and characterization 9,10-Bis(3-hydroxy-3,3-dimethyl-1-propynyl)anthracene 2-Bromo-3,6-difluorophenol 2-(Trimethylsilyl)-3,6-difluorophenyltriflate General procedure of Diels-Alder reaction Large-scale synthesis of 1,4-addutcs Deprotection of 1,4-adducts S3. X-ray analysis S4. DFT calculations S1

3 S1. Materials and methods Anhydrous solvents were purchased and used without further purifications. 9,10-dibromoanthracene, 2,5-difluorophenol, 2-methyl-3-butyn-2-ol, TMS 2 NH, Tf 2 O and 2-(trimethylsilyl)phenyl triflate were purchased by TCI. Other materials are commercially available and used without further purification. 1 H and 13 C{ 1 H}, 19 F{ 1 H} NMR spectra were acquired on a Bruker AV-400M (400 MHz), AV-500 (500 MHz). The chemical sifts were referenced with respect to TMS (δ 0.00) for 1 H, and CDCl 3 (δ 77.16) or THF-d 8 (δ 67.21) for 13 C, C 6 F 6 (δ ppm) for 19 F as internal standards. High-resolution ESI-MS spectra were measured with a Bruker microtof II (Eluent, acetone contains 1%TFA or TFANa). X-ray crystal structure analyses were performed at a Bruker APEXII ULTRA/CCD diffractometer with graphite monochromated Mo-Kα radiation. S2. Synthesis and characterization 9,10-Bis(3-hydroxy-3-dimethyl-1-butynyl)anthracene A mixture of 9,10-dibromoanthracene (9.78 g, 30 mmol), Pd(PPh 3 ) 4 (0.696 g, 0.60 mmol), CuI (0.115 g, 0.60 mmol) and 2-methyl-3-butyn-2-ol (8.8 ml, 90 mmol) in THF (200 ml) and i-pr 2 NH (100 ml) was stirred at 70 o C for 24 h under argon atmosphere. After the mixture was cooled to room temperature, the solvent was concentrated under vacuum. The resulting solid was dissolved in CH 2 Cl 2 (300 ml) and washed with 10% HCl (100 ml x 1), water (100 ml x 2). The separated organic phase was dried over MgSO 4. The crude product was purified by reprecipitation (CH 2 Cl 2 /MeCN) to give 9, 10-bis(3-hydroxy-3-dimethyl-1-butynyl)anthracene (5.82 g, 17 mmol, 57% yield) as a red powder. 1 H NMR (400 MHz, CDCl 3, r.t.): δ (m, 4H, C 14 H 8 ), (m, 4H, C 14 H 8 ), 2.21 (s, 2H, OH), 1.85 (s, 12H, CH 3 ). 1 H NMR data are matched with reported S2

4 literature (Dang, H.; Levitus, M.; Garcia-Garibay, M. A. J. Am. Chem. Soc. 2002, 124, ). 2-Bromo-3,6-difluorophenol To a THF (100 ml) solution of 2,5-difluorophenol (4.67 g, 36 mmol) and i-pr 2 NH (3.4 ml, 40 mmol) was slowly added N-bromosuccinimide (6.41 g, 36 mmol) at -40 o C. The mixture was stirred at for 30 min at -40 o C then warmed at r.t. and stirred for additional 30 min. After the reaction was quenched by 10% HCl aq. (50 ml), the mixture was diluted with Et 2 O (200 ml) and washed by water (50 ml x 2), brine (50 ml x 2). The organic phase was dried over MgSO 4. The crude product was purified by silica gel column chromatography (CHCl 3 ) to give 2-bromo-3,6-difluorophenol (4.31 g, 21 mmol, 57% yield) as a pale red oil. 1 H NMR (400 MHz, CDCl 3, r.t.): δ (m, 1H, C 6 H 2 F 2 ), (m, 1H, C 6 H 2 F 2 ), 5.66 (br s, 1H, OH); 19 F{ 1 H} NMR (376 MHz, CDCl 3, r.t.); δ (d, 1F, C 6 H 2 F 2, J = 15 Hz), (d, 1F, C 6 H 2 F 2, J = 15 Hz). NMR data were matched with the literature (Percec, V.; Imam, M. R.; Peterca, M.; Wilson, D. A.; Graf, R.; Spiess, H. W.; Balagurusamy, V. S. K.; Heiney, J. Am. Chem. Soc. 2009, 131, ). 2-(Trimethylsilyl)-3,6-difluorophenyltriflate To a THF (7.5 ml) solution of 2-bromo-3,6-difluorophenol (4.18 g, 20 mmol) was added TMS 2 NH (8.7 ml, 40 mmol) at r.t. and the mixture was refluxed for 2h. After the mixture was cooled to r.t., the solvent and unreacted TMS 2 NH was removed under vacuum. The resulting oil was dissolved in THF (15 ml) and the mixture was cooled to -100 o C. n-buli (40 mmol, 16 ml of 2.5 M hexane solution) was added dropwisely to the mixture and stirred for 30 min at -100 o C. Tf 2 O (6.6 ml, 40 mmol) was added S3

5 dropwisely to the mixture and stirred for 30 min at -100 o C. After the reaction was quenched by sat. NaHCO 3 (5 ml), the mixture was allowed to slowly warmed to r.t. The mixture was diluted with Et 2 O (150 ml) and then washed with water (50 ml x 2). The organic phase was dried over MgSO 4. The crude product was purified by silica gel column chromatography (Hexane) to give 2-(trimethylsilyl)-3,6-difluoro phenyltriflate (2.48 g, 7.4 mmol, 36% yield) as pale red oil. 1 H NMR (400 MHz, CDCl 3, r.t.): δ (m, 1H, C 6 H 2 F 2 ), (m, 1H, C 6 H 2 F 2 ), 0.45 (s, 9H, CH 3 ); 13 C{ 1 H} NMR (400 MHz, CDCl 3, r.t.): δ (d, C 6 H 2 F 2, J = 240 Hz), (d, C 6 H 2 F 2, J = 249 Hz), (q, CF 3, J = 130 Hz), (d, C 6 H 2 F 2, J = 39 Hz), (d, C 6 H 2 F 2, J = 319 Hz), (dd, C 6 H 2 F 2, J = 11, 22 Hz), (dd, C 6 H 2 F 2, J = 6, 30 Hz), 0.30 (d, CH 3, J = 4 Hz); 19 F{ 1 H} NMR (376 MHz, CDCl 3, r.t.); δ (s, 3F, CF 3 ), (s, 1F, C 6 H 2 F 2 ), (m, 1F, C 6 H 2 F 2 ). Figure S1. 1 H NMR spectrum of 2-(trimethylsilyl)-3,6-difluorophenyltriflate (400 MHz, CDCl 3, r.t.). S4

6 Figure S2. 13 C{ 1 H} NMR spectrum of 2-(trimethylsilyl)-3,6-difluorophenyltriflate (100 MHz, CDCl 3, r.t.). Figure S3. 19 F{ 1 H} NMR spectrum of 2-(trimethylsilyl)-3,6-difluorophenyltriflate (376 MHz, CDCl 3, r.t.). S5

7 General procedure of Diels-Alder reaction A mixture of anthracene derivative (0.10 mmol), benzyne precursor (0.15 mmol), CsF (24 mg, 0.15 mmol) in acetonitrile (2 ml) was stirred at 25 o C for 24 h under argon atmosphere. After the mixture was poured into water (50 ml), the resulting solid was corrected by suction filtration and dried under vacuum. The obtained reaction mixture was analyzed by 1 H NMR measurement. Run 1. Reaction of anthracene (R 1 = H) (18 mg, 0.10 mmol) with 2-(trimethylsilyl)phenyl triflate (R 2 = H) (45 mg, 0.15 mmol) afforded the reaction mixture (39 mg). Figure S4. 1 H NMR spectrum of the reaction mixture of run 1 (400 MHz, CDCl 3, r.t.). S6

8 Run 2. Reaction of anthracene (R 1 = H) (18 mg, 0.10 mmol) with 2-(trimethylsilyl)-3,6- difluorophenyltriflate (R 2 = F) (49 mg, 0.15 mmol) afforded the reaction mixture (25 mg). Figure S5. 1 H NMR spectrum of the reaction mixture of run 2 (400 MHz, CDCl 3, r.t.). Run 3. Reaction of 9,10-bis(3-hydroxy-3-dimethyl-1-butynyl)anthracene (R 1 = -C CC(CH 3 ) 2 OH) (34 mg, 0.10 mmol) with 2-(trimethylsilyl)phenyl triflate (R 2 = H) (45 mg, 0.15 mmol) afforded the reaction mixture (31 mg). Figure S6. 1 H NMR spectrum of the reaction mixture run 3 (400 MHz, CDCl 3, r.t.). S7

9 Run 4. Reaction of 9,10-bis(3-hydroxy-3-dimethyl-1-butynyl)anthracene (R 1 = -C CC(CH 3 ) 2 OH) (34 mg, 0.10 mmol) with 2-(trimethylsilyl)-3,6-difluorophenyltriflate (45 mg, 0.15 mmol) (R 2 = F) afforded the reaction mixture (38 mg). Figure S7. 1 H NMR spectrum of the reaction mixtures of run 4 (400 MHz, CDCl 3, r.t.). Large-scale synthesis of 1,4-addutcs A mixture of 9,10-bis(3-hydroxy-3,3-dimethyl-1-propynyl)anthracene (1.55 g, 4.5 mmol), 2-(trimethylsilyl)-3,6-difluorophenyltriflate (1.95 g, 5.9 mmol), CsF (0.906 g, 6.0 mmol) in acetonitrile (100 ml) was stirred at 50 o C for 16 h under argon atmosphere. After the mixture was cooled to room temperature, the solvent was concentrated under vacuum. The resulting crude product was purified by silica gel column chromatography (CH 2 Cl 2 /acetone = 10:1) to give 1,4-adduct (242 mg, 0.53 mmol, 12% yield) as a red powder, which contains 9,10-adduct and anthracene derivative (1,4-adduct: 9,10-adduct: anthracene = 65: 23: 12). 1 H NMR (400 MHz, CDCl 3, r.t.): δ (m, 2H, C 6 H 4 ), (m, 2H, C 6 H 4 ), S8

10 (m, 2H, C 6 H 4 ), 6.69 (t, 2H, C 6 H 4 F 2, J = 5.8 Hz), (m, 2H, C 6 H 4 ), 2.19 (s, 2H, OH), 1.82 (s, 12H, CH 3 ); 19 F{ 1 H} NMR (376 MHz, CDCl 3, r.t.); δ (s, 2F, C 6 H 2 F 2 ); HRMS (ESI-TOF): Calcd. for C 30 H 2 F 2 +H + : , found: m/z ([M+H] + ). Figure S8. 1 H NMR spectrum of 1,4-adduct (400 MHz, CDCl 3, r.t.) Figure S9. 1 H- 1 H COSY spectrum of 1,4-adduct (400 MHz, CDCl 3, r.t.) S9

11 Deprotection of 1,4-adduct A mixture of 1,4-adduct (0.241 mg, 0.53 mmol) and KOH (291 mg, 5.3 mmol) in i-proh (10 ml) was stirred at 80 o C for 2 h. After the mixture was cooled to room temperature, the solvent was concentrated under vacuum. The resulting solid was dissolved in CH 2 Cl 2 (20 ml) and washed with water (10 ml) x 2. The separated organic phase was dried over MgSO 4. The crude product was purified by silica gel column chromatography (eluent; CHCl 3 ) and recrystallization (CH 2 Cl 2 /hexane) to give 1,4-adduct-dp (120 mg, 0.34 mmol, 66% yield) as a pale yellow powder which contains 9,10-adduct and anthracene derivative (1,4-adduct: 9,10-adduct: anthracene = 49: 20: 31). 1 H NMR (400 MHz, CDCl 3, r.t.): δ (m, 2H, C 6 H 4 ), (m, 2H, C 6 H 4 ), (m, 2H, C 6 H 4 ), 6.70 (t, 2H, C 6 H 4 F 2, J = 5.8 Hz), (m, 2H, C 6 H 4 ), 3.79 (s, 2H, -C CH); 19 F{ 1 H} NMR (376 MHz, CDCl 3, r.t.); δ (s, 2F, C 6 H 2 F 2 ). Figure S10. 1 H NMR spectrum of 1,4-adduct-dp (400 MHz, CDCl 3, r.t.) S10

12 S3. X-ray analysis Single crystals of 1,4-adduct-dp suitable for the X-ray diffraction study were obtained by recrystallization from CH 2 Cl 2 /hexane. Crystallographic data and detailed results of refinement are summarized in Table S1. CCDC contains the supplementary crystallographic data. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via Solvents Color Table S1. Crystallographic dada CH 2 Cl 2 /Hexane Clear Formula C 30 H 24 F 2 F w Crystal size/mm 0.16 x 0.13 x 0.07 Crystal system monoclinic Space group P12 1 /c1 (#14) a/å (10) b/å (13) c/å (13) α/ o - ß/ o (13) γ/ o - V/Å (3) Z 4 D c /g cm No. of reflections measured 7677 No. of unique reflections 2864 No. observations 2520 (I > 2σ(I)) R R w GOF S11

(BHHLYP/6-31G(d)) Run R 1 R 2 Product ΔG ΔH /kcal mol -1

21 2 1,4-Adducts 19.13 7.28 3 -C CH F 9,10-Adducts 16.

92 5.08 6 1,4-Adducts 19.73 7.75 7 H F 9,10-Adducts 11.

12 (a) 9,10-Diethynylanthracene and benzyne

and 3,6-difluorobenzyne 9,10-position 1,4-position F2 F2

Anthracene and 3,6-difluorobenzyne 9,10-position

13 S4. DFT calculations Figure S2. Simulated activation parameters by DFT calculations (BHHLYP/6-31G(d)) Run R 1 R 2 Product ΔG ΔH /kcal mol -1 /kcal mol C CH H 9,10-Adducts ,4-Adducts C CH F 9,10-Adducts ,4-Adducts H H 9,10-Adducts ,4-Adducts H F 9,10-Adducts ,4-Adducts (a) 9,10-Diethynylanthracene and benzyne 9,10-position 1,4-position (b) 9,10-Diethynylanthracene and 3,6-difluorobenzyne 9,10-position 1,4-position F2 F2 F F1 1 4 (c) Anthracene and benzyne (d) Anthracene and 3,6-difluorobenzyne 9,10-position 1,4-position 9,10-position 1,4-position F2 F F F Figure S11. Transition state structures by DFT calculations (BHHLYP/6-31G(d)). S12

14 Benzyne C C C C C C H H H H Total energy = a.u. Number of imaginary frequencies = 0 3,6-Difluorobenzyne C C C C C C F F H H Total energy = a.u. Number of imaginary frequencies = 0 9,10-Diethynylanthracene C C C C C C C C C C C C H C H H C H H C H H C H C H C H Totel energy = a.u. Number of imaginary frequencies = 0 S13

15 TS of 9,10-diethynylanthracene and benzyne at 1,4-position C C C C C C C C C C C C C C C C H C H H C H H C H H C H H C H H C H C H C H Total energy = a.u. Number of imaginary frequencies = 1 ( 279i cm -1 ) TS of 9,10-diethynylanthracene and 3,6-difluorobenzyne at 1,4-positon C C C C C C C C C C C C C C C C F C H F C S14

16 H H C H H C H H C H H C H C H C H Energy = a.u. Number of imaginary frequencies = 1 ( 211i cm -1 ) TS of 9,10-diethynylanthracene and benzyne at 9,10-position C C C C C C C H H C H H C C C C H C H H C H C C C C C C H C H H C H C H C H Energy = a.u. Number of imaginary frequencies = 1 ( 226i cm -1 ) TS of 9,10-diethynylanthracene and 3,6-difluorobenzyne at 9,10-position S15

17 C C C C C C C H H C H H C C C C F C H F C H C C C C C C H C H H C H C H C H Energy = a.u. Number of imaginary frequencies = 1 ( 190i cm -1 ) TS of anthracene and benzyne at 9,10-position C C C C C C C H C C H C C C C C H C H H C H H C H H C S16

18 H H C H H C H Energy = a.u. Number of imaginary frequencies = 1 ( 232i cm -1 ) TS of anthracene and benzyne at 1,4-position C C C C C C C H H C H H C C C C H C H H C H H C C H C C H C H H C H Energy = a.u. Number of imaginary frequencies = 1 ( 287i cm -1 ) TS of anthracene and 3,6-difluorobenzyne at 9,10-position C C C C C C C H C C H C C C S17

19 C C F C H F C H H C H H C H H C H H C H Energy = a.u. Number of imaginary frequencies = 1 ( 126i cm -1 ) TS of anthracene and 3,6-difluorobenzyne at 1,4-position C C C C C C C H H C H H C C C C F C H F C H H C C H C C H C H H C H Energy = a.u. Number of imaginary frequencies = 1 ( 211i cm -1 ) S18

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