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Synlett 2008(20): 3153-3156  
DOI: 10.1055/s-0028-1087363
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Novel Synthetic Route to Dihydropyrenes

Kazufumi Chifuku, Tsuyoshi Sawada*, Takao Kihara, Kentaro Shimojo, Hidetoshi Sonoda, Yutaka Kuwahara, Hideto Shosenji, Hirotaka Ihara
Department of Applied Chemistry and Biochemistry, Kumamoto University, 2-39-1 Kurokami, Kumamoto-shi, Kumamoto 860-8555, Japan
Fax: +81(96)3423679; e-Mail: sawada@gpo.kumamoto-u.ac.jp;
Further Information

Publication History

Received 12 August 2008
Publication Date:
27 November 2008 (online)

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Abstract

We developed a new and short synthetic route to 2,7-di-tert-butyl-trans-15,16-dimethyldihydropyrene (DHP) via tetra­hydroxy[2.2]metacyclophane in four reaction steps with a total yield of 37%. 2,7-Di-tert-butyl-trans-15,16-dimethyldihydro­pyrene functionalized by acetoxy groups at 4-, 5-, 9-, 10-positions was synthesized via 5,13-di-tert-butyl-8,16-dimethyl-1,2,9,10-tetra­hydroxy[2.2]MCP in five reaction steps with a yield of 24%, and its DHP structure was determined by ¹H NMR spectroscopy and X-ray crystal-structure analysis.

Key words

cyclophanes - arenes - photochemistry - reduction - ­oxidations

8

Synthesis of 3 from 6
To a stirred suspension of 6 (100 mg, 0.24 mmol), imidazole (196 mg, 2.88 mmol), and chlorodiphenylphosphine (235 mg, 1.00 mol) in toluene (50 mL) was added iodine (243 mg, 1.00 mmol) portionwise at reflux temperature, and the mixture was refluxed for 1 h. Zinc powder (667 mg, 9.76 mmol) was added, and the mixture was refluxed for 8 h. The mixture was cooled to r.t. and washed with 1 M NaOH (50 mL), H2O (50 mL), and brine. The organic layer was dried over MgSO4, evaporated in vacuo, and purified by TLC to afford 3 (63 mg, 75%) and 7 (8 mg, 7%) as green powders.
Compound 3: mp (from n-hexane) 201-203 ˚C (lit. [4] mp 203-204 ˚C). ¹H NMR (400 MHz, 25 ˚C, CDCl3): δ = -4.04 (s, 6 H), 1.69 (s, 18 H), 8.46 (s, 4 H), 8.54 (s, 4 H).
Compound 7: mp (from n-hexane) 104-105 ˚C. FT-IR: 697, 732, 1026, 1109, 1130, 1161, 1236, 1360, 1437, 2861, 2906, 2926, 2967 cm-¹. ¹H NMR (400 MHz, 25 ˚C, CDCl3): δ =
-4.17 (s, 3 H), -4.10 (s, 3 H), 1.57 (s, 9 H), 1.60 (s, 9 H), 7.27-7.39 (m, 4 H), 7.40-7.58 (m, 4 H), 8.00-8.22 (m, 2 H), 8.33 (d, J = 7.80 Hz, 1 H), 8.38 (d, J = 7.84 Hz, 1 H), 8.43 (s. 1 H), 8.45 (s, 1 H), 8.49 (s, 1 H), 8.67 (s, 1 H), 8.82 (s, 1 H). ¹³C NMR (100 MHz, 25 ˚C, CDCl3): δ = 29.53, 29.68, 31.81, 31.86, 31.89, 31.96, 36.00, 36.03, 115.85, 120.48, 121.04, 121.59, 122.50, 122.80, 123.26, 124.51, 128.39, 128.70, 131.80, 132.26, 135.14, 136.54, 137.47, 142.10, 144,59, 146.91. HRMS-FAB+: m/z calcd for C38H41O2P + Na: 583.2775; found: 583.2776 [M+ + Na].

13

Oxidation of 6 to 11
A solution of 6 (1.00 g, 2.40 mmol) in DMSO (100 mL) was degassed in vacuo, Ac2O (10.0 ml, 97.2 mmol) was added, and the mixture was degassed in vacuo. The reaction mixture was stirred for 20 h under nitrogen at r.t. Then, H2O (100 mL) was added and the reaction mixture was neutralized by aq NH3. The reaction mixture was then filtered, and the precipitate was washed with H2O and cold MeOH, and dried in vacuo to afford 11 (959 mg, 98%) as a yellow powder; mp 233-240 ˚C (dec.); lit [¹¹] mp 230-240 ˚C (dec.). ¹H NMR (400 MHz, 25 ˚C, CDCl3): δ = 0.89 (s, 6 H), 1.29 (s, 18 H), 7.58 (s, 4 H).

15

Synthesis of 12 from 11
To a suspension of 11 (500 mg, 0.25 mmol) and zinc powder (1.61 g, 25.0 mmol) in dry CH2Cl2 (50 mL) was added Ac2O (2.5 mL, 24.3 mmol) and Et3N (5.0 mmol, 37.5 mmol). The mixture was stirred for 2.5 h under nitrogen at r.t., and then filtered through Celite. The filtrate was washed with 10 wt% aq HCl (50 mL) and sat. aq NaHCO3 (50 mL). The organic layer was dried over MgSO4 and evaporated in vacuo; the residue was recrystallized with hexane-CH2Cl2 to afford 12 (203 mg, 50%) as green needles.
Dihydropyrene 12: mp (from n-hexane-CH2Cl2): 257-258 ˚C. FT-IR: 1003, 1215, 1479, 1661, 2957, 3672 cm-¹. ¹H NMR (400 MHz, 25 ˚C, CDCl3): δ = -3.28 (s, 6 H), 1.61 (s, 18 H), 2.58 (s, 12 H), 8.45 (s, 4 H). ¹³C NMR (100 MHz, 25 ˚C, CDCl3): δ = 20.56, 29.90, 31.05, 31.70, 36.25, 116.00, 125.75, 134.93, 147.02, 169.15. MS-FAB+: m/z = 576 [M+]. Anal. Calcd for C34H40O8: C, 70.81; H, 6.99. Found: C, 70.55; H, 7.14.

17

Single crystals of 12 suitable for X-ray analysis were prepared by recrystallization from CHCl3. Diffraction data were collected on a Regaku AFC’R diffractometer at 25 ˚C with graphite monochromated Moκa (λ = 0.71069 Å) radiation. For structure analysis and refinement, computations were performed using the Crystal Structure crystallographic software package of Rigaku Corporation. The structure was solved by the direct method (SIR92). All nonhydrogen atoms were refined anisotropically. Hydrogen atoms were included, but not refined. The weighting scheme ω = 1/[σ² (Fo²) + (0.2000P)² + 0.0000P] where P = (Fo² - Fc²)². Supplementary data of 12 have been deposited with the CCDC in the CIF format (deposit No. CCDC671306).
X-ray analysis for 12: C36H42O8Cl6 (C34H40O8 + 2CHCl3), MW = 815.44, green needles, monoclinic, P21/n (# 14), Z = 2, a = 14.220 (4) Å, b = 10.2485 (19) Å, c = 14.012 (2) Å, β = 93.051 (17)˚, V = 2039.1 (7) ų, D calcd  = 1.328
g cm-³, T = 298 K, µ(Moκa) = 4.669 cm-¹, Rigaku AFC7R, Moκa (λ = 0.71069 Å), 254 parameters, R1 = 0.1193, wR2 = 0.4244, GOF = 0.901.