Alkoxyamines by Reaction of 2,2,6,6-Tetramethylpiperidine-1-oxoammonium Tetrafluoroborate with Enolates

Abstract

Alkoxyamines are prepared from the oxoammonium salt of TEMPO and enolates in one step and metal free in 47-89% yield. One of these alkoxyamines (6b) was used to polymerize styrene with a polydispersity index (PDI) = 1.42 (125 °C) and 1.49 (105 °C).

alkoxyamines - radical reaction - polymerization - ­alkylation - oxoammonium salt

References

1 Hawker CJ. Bosmann AW. Harth E. Chem. Rev.  2001,  101:  3661 

2 Benoit D. Grimaldi S. Robin S. Finet JP. Tordo P. Gnanou Y. J. Am. Chem. Soc.  2000,  122:  5929 

3 Benoit D. Chaplinski V. Braslau R. Hawker CJ. J. Am. Chem. Soc.  1999,  121:  3904 

4 Braslau R. Burrill LC. Siano M. Naik N. Howden RK. Mahal LK. Macromolecules  1997,  30:  6445 

5 Braslau R. Burrill LC. Mahal LK. Wedekind T. Angew. Chem., Int. Ed. Engl.  1997,  36:  237 

6 Jahn U. J. Org. Chem.  1998,  63:  7130 

7 Matyjaszewski K. Gaynor S. Greszta D. Mardare D. Shigemoto T. Macromol. Symp.  1995,  98:  73 

8 Hammouch SO. Catala JM. Macromol. Rapid Commun.  1996,  17:  149 

9 Bergbreiter DE. Walchuk B. Macromolecules  1998,  31:  6380 

10 Dao J. Benoit D. Hawker CJ. J. Polym. Sci., Part A: Polym. Chem.  1998,  36:  2161 

11a Merbouh N. Bobbitt JM. Brückner C. Tetrahedron Lett.  2001,  42:  8793 

11b de Noy AEJ. Besemer AC. van Bekkum H. Synthesis  1996,  1153 

11c Schnatbaum K. Schäfer HJ. Synthesis  1999,  864 

11d Schämann M. Schäfer HJ. Eur. J. Org. Chem.  2003,  351 

12 Takata T. Tsujino Y. Nakanishi S. Nakamura K. Yoshida E. Endo T. Chem. Lett.  1999,  937 

13 Kobatake S. Harwood HJ. Quirk RP. Priddy DB. J. Polym. Sci., Part A: Polym. Chem.  1998,  36:  2555 

14 Hunter DH. Barton DHR. Motherwell WJ. Tetrahedron Lett.  1984,  25:  603 

15 Golubev VA. Miklyush RV. Rozantsev ZG. Izvest. Akadem. Nauk SSR, Ser. Khim.  1972,  656 ; Chem. Abstr. 1972, 77, 101344

16 Yoshida E. Ishizone T. Hirao A. Nakahama S. Takata T. Endo T. Macromolecules  1994,  27:  3119 

17 Sheinkman AK. Chmilenko TS. Vdovkina GG. Zhurnal Organicheskoi Khimii  1983,  19:  2218 ; J. Org. Chem. USSR 1983, 19, 1933

18 Bobbitt JM. Guttermuth CFM. Ma Z. Tang H. Heterocycles  1990,  30:  1131 

19

We thank the Degussa AG Hüls for a research sample of TEMPO.

20

General Procedure for the Preparation of 6a,b,d-f: Sodium hydride (124 mg, 3.10 mmol) was stirred with 3.0 mmol of 4 in 8 mL anhyd THF at 0 °C. Compound 4g was deprotonated at -78 °C and LDA was used instead of sodium hydride. When the hydrogen evolution had ceased, the suspension was warmed up to r.t. and 781 mg (3.2 mmol) of 2 [18] were added. After stirring for 2 h, 1.5 mL H₂O were added and the organic phase was separated. The aq phase was washed with Et₂O (2 × 10 mL) and the combined organic phase was dried over MgSO₄. The Et₂O was evaporated and the crude product was purified by flash chromatography.
Compounds 6a,b,d-g were characterized by ¹H NMR (300 MHz, CDCl₃) and ¹³C NMR (75 MHz, CDCl₃), MS and elemental analysis.
6a: ¹H NMR: δ = 1.00-1.07 (m, 6 H, 2 × CH₃), 1.20 (s, 6 H, 2 × CH₃), 1.28 (t, J = 7.0 Hz, 3 H, CH₂ CH ₃ ), 1.46 (s, 6 H, 3 × CH₂), 2.30 (s, 3 H, CH₃), 4.20 (q, 2 H, OCH₂), 4.80 (s, 1 H, 2-H) ppm. ¹³C NMR: δ = 12.9 (q, CH₂ CH ₃ ), 15.8 (t, CH₂), 19.0 (2 q, CH₃), 25.3 (q, C-4), 31.4, 31.8 (2 q, CH₃), 38.9 (2 t, CH₂), 58.9 [2 s, C(CH₃)₂], 60.3 (t, OCH₂), 92.5 (d, C-2), 166.6 (s, C-1), 201.5 (s, C-3) ppm. MS (ESI, ES+): m/z (%) = 286 (77) [M + H⁺], 142 (20) [C₁₉H₁₈NH₂ ⁺], 141 (100) [C₉H₁₉N⁺], 126 (76) [C₉H₁₈ ⁺], 61 (17). Anal. Calcd for C₁₅H₂₇NO₄ (285.38): C, 63.13; H, 9.54; N, 4.91. Found: C, 63.03; H, 9.61; N, 4.94.
6b: Mp: 29-30 °C. R_f = 0.09 (PE-Et₂O 20:1). ¹H NMR: δ = 1.01, 1.20 (2 s, 12 H, 4 × CH₃), 1.26-1.31 (m, 6 H, 2 × CH₃), 1.42-1.46 (m, 6 H, 3 × CH₂), 4.17-4.30 (m, 4 H, 2 × OCH₂), 4.92 (s, 1 H, 2-H) ppm. ¹³C NMR: δ = 13.2 (2 q, CH₂ CH ₃), 16.1 (t, CH₂), 19.3 (2 q, CH₃), 31.7 (2 q, CH₃), 39.4 (2 t, CH₂), 59.4 [2 s, C(CH₃)₂], 60.7 (2 t, OCH₂), 86.0 (d, C-2), 166.4 (2 s, C-1, C-3) ppm. MS (ESI, ES+): m/z (%) = 316 (15) [M + H⁺], 192 (35), 141 (22) [C₉H₁₉N⁺], 126 (100) [C₉H₁₈]. Anal. Calcd for C₁₆H₂₉NO₅ (315.40): C, 60.93; H, 9.27; N, 4.44. Found: C, 61.01; H, 9.42; N, 4.40.
6d: R_f = 0.07 (PE-Et₂O 20:1). Mp 54-55 °C. ¹H NMR:
δ = 0.98 (s, 6 H, 3 × CH₂), 2.21 (2 s, 6 H, 1-H, 5-H), 4.92 (s, 1 H, 3-H), 1.20 (s, 6 H, 3 × CH₂), 1.45 (s, 6 H, 3 × CH₂) ppm. ¹³C NMR: δ = 16.8 (t, CH₂), 20.0 (2 q, CH₃), 26.9 (2 q, C-1, C-5), 32.8 (2 q, CH₃), 40.3 (2 t, CH₂), 59.9 [2 s, C(CH₃)₂], 101.4 (d, C-3), 203.6 (2 s, C-2, C-4) ppm. MS (ESI, ES+): m/z (%) = 256 (24) [M + H⁺], 156 (2) [C₉H₁₈N=O⁺], 142 (30) [C₉H₁₈NH₂ ⁺], 141 (97) [C₉H₁₉N⁺], 126 (100) [C₉H₁₈ ⁺], 70 (4), 60 (25), 43 (8) [CH₃CO⁺]. Anal. Calcd for C₁₄H₂₅NO₃ (255.35): C, 65.85; H, 9.87; N, 5.49. Found: C, 65.71; H, 9.98; N, 5.29.
6e: R _f = 0.22 (PE-Et₂O 10:1). Mp 63 °C. ¹H NMR: δ = 0.83, 0.99 (2 s, 6 H, 2 × CH₃), 1.13 (t, J = 7.1 Hz, 3 H, CH₂ CH ₃), 1.18, 1.29 (2 s, 6 H, 2 × CH₃), 1.40-1.48 (m, 6 H, 3 × CH₂), 4.16 (q, 2 H, OCH₂), 5.41 (s, 1 H, 2-H), 7.43-7.60 (m, 3 H, CH_arom.), 8.13-8.16 (m, 2 H, CH_arom.) ppm. ¹³C NMR: δ = 13.9 (q, CH₂ CH ₃), 17.0 (t, CH₂), 20.2 (2 q, CH₃), 32.5, 33.1 (2 q CH₃), 40.1 (2 t, CH₂), 60.0, 60.4 [2 s, C(CH₃)₂], 61.6 (t, OCH₂), 92.9 (d, C-2), 128.4, 129.8, 133.5, (5 d, CH_arom.), 134.6 (s, C_arom.), 168.2 (s, C-1), 193.6 (s, C-3) ppm. MS (ESI, ES+): m/z (%) = 348 (38) [M + H⁺], 246 (5), 243 (12), 156 (8) [C₉H₁₈N=O⁺], 141 (75) [C₉H₁₉N⁺], 126(55) [C₉H₁₈ ⁺], 122 (50), 105 (100) [C₆H₅CO⁺]. Anal. Calcd for C₂₀H₂₉NO₄ (347.45): C, 69.14; H, 8.41; N, 4.03. Found: C, 69.16; H, 8.31; N, 3.91.
6f: R _f = 0.18 (PE-Et₂O 15:1). Mp 67 °C. ¹H NMR: δ = 0.83 (s, 3 H, CH₃), 1.06 (s, 6 H, 2 × CH₃), 1.26 (s, 3 H, CH₃), 1.40-1.47 (m, 6 H, 3 × CH₂), 2.24 (s, 3 H, 4-H), 5.59 (s, 1 H, 2-H), 7.43-7.59 (m, 3 H, CH_arom.), 8.03-8.10 (m, 2 H, CH_arom.) ppm. ¹³C NMR: δ = 16.9 (t, CH₂), 20.2, 20.3 (2 q, CH₃), 26.7 (q, C-4), 32.8, 33.0 (2 q, CH₃), 40.2 (2 t, CH₂), 60.0, 60.2 [2 s, C(CH₃)₂], 100.1 (d, C-2), 128.6, 129.9, 133.8, (5 d, CH_arom.), 134.6 (s, C_arom.), 195.3 (s, C-1), 203.5 (s, C-3) ppm. MS (ESI, ES+): m/z (%) = 318 (60) [M + H⁺], 276 (3) [M + H⁺ - OCCH₂], 246 (2), 184 (4), 156 (3) [C₉H₁₈N=O⁺], 141 (100) [C₉H₁₉N⁺], 126 (80) [C₉H₁₈ ⁺], 122 (30), 105 (100) [C₆H₅CO⁺], 60 (10). Anal. Calcd for C₁₉H₂₇NO₃ (317.42): C, 71.89; H, 8.57; N, 4.41. Found: C, 72.00; H, 8.56; N, 4.04.
6g: R_f = 0.30 (CH-EtOAc, 10:1). Mp 27 °C. ¹H NMR (400 MHz, CDCl₃): δ = 1.00-1.01 (m, 6 H, 2 × CH₃), 1.11-1.17 (m, 6 H, 2 × CH₃), 1.32-1.53 (m, 6 H, 3 × CH₂), 1.56-1.64 (m, 1 H, 4-H), 1.71-1.81 (m, 1 H, 5-H), 1.84-2.04 (m, 3 H, 3-H, 4-H, 5-H), 2.08-2.16 (m, 1 H, 3-H), 2.23-2.29 (m, 1 H, 6-H), 2.73-2.80 (m, 1 H, 6-H), 4.14-4.17 (m, 1 H, 2-H) ppm. ¹³C NMR (100 MHz, CDCl₃): δ = 17.1 (t, CH₂), 20.1 (2 q, CH₃), 22.0 (t, C-4), 28.4 (t, C-5), 34.8 (t, C-3), 33.5, 33.9 (2 q, CH₃), 40.2 (2 t, CH₂), 40.9 (t, C-6), 59.7 [2 s, C(CH₃)₂], 89.2 (d, C-2), 211.5 (s, C-1) ppm. MS (ESI, ES+): m/z (%) = 254 (100) [M + H⁺], 142 (55) [C₉H₁₈NH₂ ⁺], 126 (92) [C₉H₁₈ ⁺], 113 (30) [M + H⁺ - C₉H₁₉N], 85 (28) [113 - CO], 67 (80). Anal. Calcd for C₁₅H₂₇NO₂ (253.38): C, 71.10; H, 10.74; N, 5.53. Found: C, 70.96; H, 11.02; N, 5.39.
Monodeacetylated dehydrodimer of 5d: MS (ESI, ES⁺): m/z (%) = 155 (7) [M + H⁺]; Monodeacetylated dehydrodimer of 5f: MS (ESI, ES⁺): m/z (%) = 279 (5) [M + H⁺].

21a Howell BA. Priddy BC. Li IQ. Smith PB. Kastl PE. Polym. Bull.  1996,  31:  5955 

21b Dao J. Benoit D. Hawker CJ. J. Polym. Sci., Part A: Polym. Chem.  1998,  36:  2161 

22a Bordwell FG. Harrelson JA. Satish AV. J. Org. Chem.  1989,  54:  3101 

22b Kern JM. Federlin P. Tetrahedron Lett.  1977,  10:  837 

23

We thank the Zentrale Forschung der Bayer AG, Krefeld for the molecular weight determination.

24a Marque S. LeMercier C. Tordo P. Fischer H. Macromolecules  2000,  33:  4403 

24b Sobek J. Martschke R. Fischer H. J. Am. Chem. Soc.  2001,  123:  2849 

24c

A. Studer, University of Münster, personal communication.

25 Wetter C. Jantos K. Woithe K. Studer A. Org. Lett.  2003,  5:  2899