Oxazoline chemistry â Part IV: Synthesis and characterization of ...

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Barclay et al. 1489 15 min. This mixture was then filtered to remove any undissolved material. To the rapidly stirring (clear and colourless) solution was added (via syringe) 8.0 mL (94 mmol) of 1 in a single portion. A white precipitate began to form almost immediately. Stirring was continued for a further 12 h at RT, and the resulting solid was isolated by filtration. This material was then washed thrice with Et 2 O (35 mL) and then allowed to dry in air. Yield 8.0 g (84%) of a white, slightly hygroscopic solid. Crystals of 5, suitable for X-ray diffraction, grew after a CH 2 Cl 2 solution of 5, layered with Et 2 O, was left standing for several days at RT. mp > 105 °C (decomposition temperature (decomp.)). IR: 1650 (st). 1 H NMR (250 MHz) δ: 4.50 (t, 2H, J = 9.8, CH 2 O), 3.98 (t, 2H, J = 9.8, CH 2 N), 2.27 (s, 3H, CH 3 ). Calcd. for C 8 H 14 N 2 O 2 Cl 2 Zn·(H 2 O) (%): C 29.72, H 4.55, N 8.67; found: C 29.72, H 4.97, N 8.63. Synthesis of [dibromobis{η 1 -N-(2-methyl-2-oxazoline)}zinc] (6) In a reaction analogous to that used to produce 5, zinc bromide (1.0 g, 4.4 mmol) in Et 2 O was treated with 1 (2.1 equiv). Yield 1.6 g (92%, hygroscopic solid). mp > 72 °C (decomp.). IR: 1650 (st). 1 H NMR (250 MHz) δ: 4.50 (t, 2H, J = 9.8, CH 2 O), 4.00 (t, 2H, J = 9.8, CH 2 N), 2.29 (s, 3H, CH 3 ). Calcd. for C 8 H 14 N 2 O 2 ZnBr 2·0.5(H 2 O): C 23.76, H 3.74, N 6.93; found: C 23.53, H 3.63, N 6.85. Synthesis of [diiodobis{η 1 -N-(2-methyl-2-oxazoline)}zinc] (7) As for 5, zinc iodide (3.0 g, 9.4 mmol), suspended in Et 2 O–THF (60 mL : 10 mL), was treated with 2.4 mL (28 mmol) of 1. Yield 4.0 g (87%, hygroscopic white solid). Crystals, suitable for X-ray diffraction, were grown from a solution of 3 (CH 2 Cl 2 layered with Et 2 O) that had been left standing at RT for several days. mp > 94 °C (decomp.). IR: 1650 (st). 1 H NMR (250 MHz) δ: 4.50 (t, 2H, J = 9.8, CH 2 O), 4.02 (t, 2H, J = 9.8, CH 2 N), 2.29 (s, 3H, CH 3 ). Calcd. for C 8 H 14 N 2 O 2 ZnI 2·0.25(H 2 O): C 19.45, H 2.96, N 5.67; found: C 19.21, H 2.76, N 5.57. Synthesis of [dichlorobis{η 1 -N-(2,4,4-trimethyl-2- oxazoline)}zinc] (8) As for 5, zinc chloride (1.2 g, 8.8 mmol) in Et 2 Owas treated with 2 (2.2 mL, 17 mmol), and the solid was washed with Et 2 O (2 × 35 mL) and petroleum ether (50 mL); the product can be further recrystallized from a 1:1 mixture of CH 2 Cl 2 –Et 2 O. Yield 2.0 g (65%). mp > 124 °C (decomp.). IR: 1635 (st). 1 H NMR (250 MHz) δ: 4.17 (s, 2H, CH 2 O), 2.27 (s, 3H, N=C-CH 3 ), 1.61 (s, 6H, CH 3 ). Calcd. for C 12 H 22 N 2 O 2 Cl 2 Zn·0.5(CH 2 Cl 2 ): C 37.06, H 5.72, N 6.92; found: C 37.29, H 5.86, N 6.92. Synthesis of [dibromobis{η 1 -N-(2,4,4-trimethyl-2- oxazoline)}zinc] (9) As for 5, using ZnBr 2 (1.4 g, 6.2 mmol; ether suspension) and 2 (1.7 mL, 13 mmol). Yield 2.7 g (96%). mp > 172 °C (decomp.). IR: 1625 (st). 1 H NMR (250 MHz) δ: 4.18 (s, 2H, CH 2 O), 2.29 (s, 3H, N=C-CH 3 ), 1.68 (s, 6H, CH 3 ). Calcd. for C 12 H 22 N 2 O 2 Br 2 Zn: C 31.92, H 4.91, N 6.20; found: C 32.16, H 4.59, N 6.21. Synthesis of [diiodobis{η 1 -N-(2,4,4-methyl-2- oxazoline)}zinc] (10) As for 5, ZnI 2 (3.3 g, 10 mmol; ether suspension) was treated with 2 (2.7 mL, 21 mmol). Yield 4.9 g (90%). Crystals, suitable for X-ray diffraction, grew from a sealed solution of 10 (CH 2 Cl 2 ) layered with Et 2 O, after standing at RT for several days. mp > 159 °C (decomp.). IR: 1630 (st). 1 H NMR (250 MHz) δ: 4.17 (s, 2H, CH 2 O), 2.27 (s, 3H, N=C- CH 3 ), 1.61 (s, 6H, CH 3 ). Calcd. for C 16 H 18 N 2 O 2 ZnI 2 (%): C 26.42, H 4.06, N 5.14, found: C 26.27, H 3.86, N 5.02. Synthesis of [dichlorobis{η 1 -N-(2-phenyl-2- oxazoline)}zinc] (11) As for 5, ZnCl 2 (2.0 g, 15 mmol) in Et 2 O (125 mL) was treated with 3 (3.9 mL, 30 mmol), and the resulting white solid was washed with Et 2 O (2 × 15 mL) and then air-dried. Yield 4.77 g (74%). mp > 179 °C (decomp.). IR: 1618 (st). 1 H NMR δ: 7.78 (d, 2H, J = 7.5, ArH), 7.61 (t, 1H, ArH), 7.41 (t, 2H, J = 7.6, ArH), 4.33 (m, 4H, CH 2 CH 2 ). Calcd. for C 16 H 18 N 2 O 2 Cl 2 Zn: C 50.20, H 4.21, N 6.51; found: C 50.47, H 4.26, N 6.68. Synthesis of [dibromobis{η 1 -N-(2-phenyl-2- oxazoline)}zinc] (12) As for 5, ZnBr 2 (2.1 g, 9.3 mmol) in Et 2 O (100 mL) was treated with 3 (2.5 mL, 19 mmol), and the solid was washed with Et 2 O (2 × 15 mL) and then air-dried. Yield 4.71 g (48%). mp > 170 °C (decomp.). IR: 1620 (st). 1 H NMR δ: 7.76 (d, 2H, J = 8.0, ArH), 7.58 (t, 1H, ArH), 7.35 (t, 2H, J = 7.9, ArH), 4.47 (m, 4H, CH 2 CH 2 ). Calcd. for C 16 H 18 N 2 O 2 ZnBr 2 : C 41.61, H 3.49, N 5.39; found: C 41.66, H 3.49, N 5.30. Synthesis of [diiodobis{η 1 -N-(2-phenyl-2-oxazoline)}zinc] (13) As for 5, ZnI 2 (1.4 g, 4.4 mmol) was suspended in Et 2 O (25 mL), and the mixture was then treated with 3 (1.1 mL, 8.4 mmol), and the light yellow solid was washed with Et 2 O (2 × 10 mL) and then air-dried. Yield 2.55 g (99%). mp > 193 °C (decomp.). IR: 1620 (st). 1 H NMR δ: 7.76 (d, J = 7.9, 2H, ArH), 7.61 (t, 1H, ArH), 7.38 (t, 2H, J = 8.0, ArH), 4.43 (m, 4H, CH 2 CH 2 ). Calcd. for C 16 H 18 N 2 O 2 ZnI 2 (%): C 35.24, H 2.96, N 4.57; found: C 34.90, H 2.97, N 4.43. Synthesis of [dichlorobis{η 1 -N-(4,4-dimethyl-2-phenyl-2- oxazoline)}zinc] (14) A sample of ZnCl 2 (2.25 g, 16.5 mmol) was dissolved in 100 mL of Et 2 O, and the solution was then filtered. Compound 4 (5.6 mL, 33 mmol) was added, and the mixture was then stirred at RT for 2 h. The resulting white solid was collected by filtration and washed with Et 2 O (2 × 25 mL). Yield 4.2 g (58%). mp > 174 °C (decomp.). IR: 1620 (st). 1 H NMR δ: 7.86 (m, 2H, ArH), 7.28 (m, 3H, ArH), 3.95 (s, 2H, CH 2 ), 1.25 (s, 6H, CH 3 ). Calcd. for C 22 H 26 N 2 O 2 Cl 2 Zn: C 54.29, H 5.38, N 5.76; found: a reproducible elemental analysis (±0.4%) could not be obtained for this material. Synthesis of [dibromobis{η 1 -N-(4,4-dimethyl-2-phenyl-2- oxazoline)}zinc] (15) As for 5, ZnBr 2 (2.0 g, 8.9 mmol) in Et 2 O (100 mL) was treated with 4 (3.0 mL, 18 mmol), then stirred for 2 h, and © 2003 NRC Canada
1490 Can. J. Chem. Vol. 81, 2003 then evaporated at RT. Yield 2.0 g (65%). mp > 168 °C (decomp.). IR: 1618 (st). 1 H NMR δ: 7.86 (m, 2H, ArH), 7.28 (m, 3H, ArH), 3.95 (s, 2H, CH 2 ), 1.25 (s, 6H, CH 3 ). Calcd. for C 22 H 26 N 2 O 2 ZnBr 2 : C 45.90, H 4.55, N 4.87; found: C 45.68, H 4.46, N 4.84. Single crystal X-ray structure determinations X-ray structure of 7 Suitable white crystals were obtained by slow diffusion of Et 2 O into a CHCl 3 solution of the complex. Diffraction data were collected on a Nonius Kappa-CCD diffractometer equipped with a 95 mm CCD camera and a k-goniostat, using graphite-monochromated Cu Kα radiation. Data were reduced to F o 2 values. A numerical absorption correction was applied using Gaussian integration (27), with max and min transmission factors of 0.024 and 0.009, respectively. The structure was solved by Patterson interpretation, using the program DIRDIF-96 (28). Isotropic and full matrix anisotropic least-squares refinements were carried out using SHELXL-97 (29). All non-H atoms were refined anisotropically, except N2, C5, and O2, which were isotropically refined. All the hydrogen atom positions were geometrically calculated and refined riding on their parent atoms. The molecular plots were made with the EUCLID program package (30). The WINGX program system (31) was used throughout the structure determinations. X-ray structures of 10–13 and 15 Suitable crystals were grown from solutions of the complexes in dichloromethane that had been layered with Et 2 O and allowed to stand at RT (or at –10 °C) for several days. Crystals were mounted on a glass fibre, covered in epoxy, and data was collected on a Smart 1000 CCD diffractometer using Mo Kα radiation (graphite monochromated). Isotropic and full matrix anisotropic least-squares refinements were carried out using SHELXL-97 (29). It should be noted that complex 15 has twofold imposed crystallographic symmetry. Acknowledgements The authors are indebted to the support of the Natural Science and Engineering Research Council (NSERC) (RAG), Acadia University (RAG), and MCYT (BQU2002–02623: IdR). Mr. Ramsey E. Beveridge is thanked for recording some NMR spectra. References 1. (a) S. Rahuel-Clermont and M.F. Dunn. The biological chemistry of zinc. In Copper and zinc in inflammatory and degenerative diseases. Edited by K.D. Rainsford, R. Milanino, J.R.J. Sorenson, and G.P. Velo. Kluwer Academic Publications, Boston. 1998. Chap 4, pp. 47–59; (b) J.F. Riordan. Med. Clin. N. Am. 60, 661 (1976); (c) B.L. Vallee and D.S. Auld. Biochemistry, 29, 5647 (1990); (d) C.L. Keen and M.E. Gershwin. Ann. Rev. Nutr. 10, 415 (1990); (e) B.L. Vallee and D.S. Auld. Acc. Chem. Res. 26, 543 (1993). 2. F.A. Cotton and G. Wilkinson. Advanced inorganic chemistry. 4th ed. John Wiley & Sons, Toronto. 1980. Chap 19, pp. 589– 616. 3. C. 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