A Facile Method for the Stereoselective Preparation of (1Z,3E)-Dienyl Ethers via 1,4-Elimination of 1,4-Dialkoxy-(2Z)-alkenes with n-Butyllithium

Abstract

Treatment of 1-alkoxy-4-methoxy-(2Z)-alkenes or 1-sil­oxy-4-methoxy-(2Z)-alkenes with n-butyllithium in diethyl ether is shown to afford the corresponding (1Z,3E)-dienyl, alkyl or silyl ethers, respectively, in high stereoselectivity via a facile 1,4-elimination. The scope and the regio- and stereochemical features of the synthetic method are described.

1,4-eliminations - dienyl ethers - dienyl acetals - stereoselective synthesis - precoordinations

References and Notes

For reviews, see:

1a Tomooka K. In The Chemistry of Organolithium Compounds   Vol. 2:  Rappoport Z. Marek I. John Wiley and Sons Ltd.; Chichester: 2004.  p.749-828  

1b Clayden J. In Organolithiums: Selectivity for Synthesis   Baldwin JE. Williams RM. Pergamon; Manchester: 2002.  Chap. 8.

1c Tomooka K. Yamamoto H. Nakai T. Liebigs Ann./Recl.  1997,  1275 

1d Nakai T. Mikami K. Org. React.  1994,  46:  105 

1e Brückner R. In Comprehensive Organic Synthesis   Vol. 6:  Trost BM. Fleming I. Pergamon; Oxford: 1991.  Chap. 4.6.

2a Casiraghi G. Zanardi F. Appendino G. Rassu G. Chem. Rev.  2000,  100:  1929 

2b Ishida A. Mukaiyama T. Bull. Chem. Soc. Jpn.  1977,  50:  1161 

3a Inui M. Hosokawa S. Nakazaki A. Kobayashi S. Tetrahedron Lett.  2005,  46:  3245 

3b Suzuki T. Inui M. Hosokawa S. Kobayashi S. Tetrahedron Lett.  2003,  44:  3713 

4 Danishefsky S. Kitahara T. J. Am. Chem. Soc.  1974,  96:  7807 

5 For a review of 1,3-dienyl silyl ethers (silyl dienol ethers), see: Brownbridge P. Synthesis  1983,  85 

Previous preparation of 1,3-dienyl silyl ethers:

6a Choi J. Imai E. Mihara M. Oderaotoshi Y. Minakata S. Komatsu M. J. Org. Chem.  2003,  68:  6164 

6b Janey JM. Iwama T. Kozmin SA. Rawal VH. J. Org. Chem.  2000,  65:  9059 

6c Moreno MJSM. Martins RMLM. Melo MLS. Neves ASC. Chem. Lett.  1997,  529 

6d Tominaga Y. Kamio C. Hosomi A. Chem. Lett.  1989,  1761 

6e Iqbal J. Khan MA. Synth. Commun.  1989,  19:  515 

6f Cazeau P. Duboudin F. Moulines F. Babot O. Dunogues J. Tetrahedron  1987,  43:  2089 

6g Colvin EW. Thom IG. Tetrahedron  1986,  42:  3137 

6h Casey CP. Jones CR. Tukada H. J. Org. Chem.  1981,  46:  2089 

6i Hirai K. Suzuki H. Morooka Y. Ikawa T. Tetrahedron Lett.  1980,  21:  3413 

6j Miller RD. McKean DR. Synthesis  1979,  730 

6k House HO. Czuba LJ. Gall M. Olmstead HD. J. Org. Chem.  1969,  34:  2324 

Previous preparation of alkyl 1,3-dienyl ethers:

7a Gilbert JC. Weerasooriya U. J. Org. Chem.  1983,  48:  448 

7b Hiranuma H. Miller SI. J. Org. Chem.  1982,  47:  5083 

7c Dowd P. Weber W. J. Org. Chem.  1982,  47:  4774 

7d Kluge AF. Cloudsdale IS. J. Org. Chem.  1979,  44:  4847 

7e Earnshaw C. Wallis CJ. Warren S. J. Chem. Soc., Perkin Trans. 1  1979,  3099 

8 A similar type of 1,4-elimination reaction has been reported using alkenyl acetals: Canepa C. Prandi C. Sacchi L. Venturello P. J. Chem. Soc., Perkin Trans. 1  1993,  1875 

9

Prepared in three steps: (i) t-BuMe₂SiOCH₂CºCH, n-BuLi, THF, -78 °C then n-BuCHO, -78 °C to r.t.; (ii) NaH, MeI, THF, 0 °C to r.t.; (iii) H₂ (1 atm), 5% Lindlar cat., quinoline, MeOH, r.t.

10

All stereoisomers were identified by ¹H NMR comparisons of the authentic samples prepared from (EtO)₂P(O)CH₂OP via the literature procedure (ref. 7d).

11

Prepared from POCH₂CºCH according to the same three-step procedure as described for 1b (ref. 9).

12

Typical Procedure for the Preparation of 1,3-Dienyl Ethers 2 To a solution of 1 (1.0 equiv, 0.25 M) in Et₂O was added a 1.6 M n-BuLi solution in n-hexane (1.5 equiv) at -40 °C to 0 °C and the mixture was stirred for 2-4 h at the same temperature. The resulting mixture was quenched with H₂O and extracted with Et₂O. The combined extract was washed with brine, dried over NaSO₄ and concentrated. The residue was purified by chromatography on silica gel to afford the corresponding 1,3-dienyl ether 2.
Selected Spectroscopic Data(2 Z )-1-( tert -Butyldimethylsilyloxy)-4-methoxy-2-butene ( 1a) Colorless oil. ¹H NMR (270 MHz, CDCl₃): δ = 5.70 (1 H, dtt, J = 11.1, 5.9, 1.4 Hz, 2- or 3-H), 5.57 (1 H, dtt, J = 11.1, 5.9, 1.4 Hz, 2- or 3-H), 4.24 (1 H, dd, J = 5.9, 1.4 Hz, 1-H), 3.99 (1 H, dd, J = 5.9, 1.4 Hz, 4-H), 3.33 (3 H, s, OCH₃), 0.90 [9 H, s, SiC(CH₃)₃], 0.07 [6 H, s, Si(CH₃)₂]. ¹³C NMR (68 MHz, CDCl₃): δ = 132.6, 126.7, 68.3, 59.5, 58.0, 26.0, 18.4, -5.0. IR (film): 3020, 2948, 2924, 2884, 2852, 1475, 1470, 1406, 1362, 1334, 1254, 1190, 1092, 1006, 956, 912, 838, 776 cm^-1. Anal. Calcd for C₁₁H₂₄O₂Si: C, 61.05; H, 11.18. Found: C, 61.17; H, 11.48.
(2 Z )-1-(Benzyloxymethoxy)-4-methoxy-2-octene ( 1f) Colorless oil. ¹H NMR (270 MHz, CDCl₃): δ = 7.40-7.27 (5 H, m, Ph), 5.82-5.72 (1 H, m, 2-H), 5.49-5.39 (1 H, m, 3-H), 4.78 (2 H, s, OCH₂O), 4.62 (2 H, s, OCH₂Ph), 4.27 (1 H, ddd, J = 12.4, 7.3, 1.4 Hz, 1-CH₂), 4.15 (1 H, ddd, J = 12.4, 6.1, 1.4 Hz, 1-CH₂), 3.94-3.85 (1 H, m, 4-H), 3.25 (3 H, s, OCH₃), 1.68-1.52 (1 H, m, 5-CH₂), 1.47-1.18 (5 H, m, 5-, 6-, and 7-CH₂), 0.88 (3 H, t, J = 6.8 Hz, 8-CH₃). ¹³C NMR (68 MHz, CDCl₃): δ = 137.6, 134.2, 128.7, 128.3, 127.7, 127.6, 93.8, 76.6, 69.3, 63.2, 56.1, 35.2, 27.4, 22.7, 14.1. IR (film): 3060, 3024, 2928, 2872, 2816, 1496, 1454, 1402, 1380, 1206, 1190, 1168, 1102, 1048, 962, 958, 736, 698 cm^-1. Anal. Calcd for C₁₇H₂₆O₃: C, 73.34; H, 9.41. Found: C, 73.42; H, 9.63.
(1 Z )-1-( tert -Butyldimethylsilyloxy)-1,3-butadiene ( 2a) [16]
Colorless oil; purified by chromatography on silica gel (hexane-Et₂O = 100:1 to 20:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.76 (1 H, dddd, J = 17.3, 10.7, 10.3, 1.1 Hz, 3-H), 6.19 (1 H, ddd, J = 5.9, 1.1, 1.1 Hz, 1-H), 5.20 (1 H, dd, J = 10.7, 5.9 Hz, 2-H), 5.07 (1 H, m, J = 17.3, 2.0 Hz, 4 _cis -H), 4.89 (1 H, ddd, J = 10.3, 2.0, 1.1 Hz, 4 _trans -H), 0.94 [9 H, s, SiC(CH₃)₃], 0.16 [6 H, s, Si(CH₃)₂]. ¹³C NMR (68 MHz, CDCl₃): δ = 140.4, 129.8, 112.9, 111.1, 25.7, 18.4, -5.3. IR (film): 3080, 2952, 2928, 2884, 2856, 1642, 1594, 1472, 1438, 1392, 1362, 1254, 1174, 1080, 998, 928, 890, 840, 784 cm^-1.
(1 Z ,3 E )-1-( tert -Butyldimethylsilyloxy)-1,3-octadiene ( 2b) Colorless oil; purified by chromatography on silica gel (hexane-EtOAc = 100:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.40 (1 H, ddd, J = 15.6, 10.8, 1.1 Hz, 3-H), 6.09 (1 H, d, J = 5.9 Hz, 1-H), 5.55 (1 H, dt, J = 15.6, 6.8 Hz, 4-H), 5.13 (1 H, dd, J = 10.8, 5.9 Hz, 2-H), 2.14-2.02 (2 H, dt, J = 6.8, 6.8 Hz, 5-CH₂), 1.44-1.24 (4 H, m, 6-CH₂ and 7-CH₂), 0.94 [9 H, s, SiC(CH₃)₃], 0.89 (3 H, t, J = 7.0 Hz, 8-CH₃), 0.15 [6 H, s, Si(CH₃)₂]. ¹³C NMR (68 MHz, CDCl₃): δ = 138.2, 130.9, 122.8, 110.8, 32.7, 31.8, 25.7, 22.4, 18.4, 14.1, -5.2. IR (film): 3028, 2952, 2924, 2852, 1654, 1612, 1470, 1410, 1362, 1254, 1156, 1112, 1050, 1006, 972, 838, 780 cm^-1. Anal. Calcd for C₁₄H₂₈OSi: C, 69.93; H, 11.74. Found: C, 69.70; H, 12.03.
(1 Z ,3 E )-1-( tert -Butyldimethylsilyloxy)-4-methoxy-1,3-butadiene ( 2c) Pale yellow oil; purified by chromatography on silica gel (hexane-Et₂O = 30:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.55 (1 H, d, J = 13.0 Hz, 4-H), 6.06 (1 H, d, J = 5.9 Hz, 1-H), 5.84 (1 H, dd, J = 13.0, 10.8 Hz, 3-H), 5.05 (1 H, dd, J = 10.8, 5.9 Hz, 2-H), 3.59 (3 H, s, OCH₃), 0.94 [9 H, s, SiC(CH₃)₃], 0.15 [6 H, s, Si(CH₃)₂]. ¹³C NMR (68 MHz, CDCl₃): δ = 148.2, 136.6, 106.5, 98.9, 56.2, 25.7, 18.4, -5.2. IR (film): 2948, 2928, 2892, 2852, 1656, 1608, 1470, 1406, 1362, 1332, 1256, 1208, 1166, 1136, 1124, 1064, 938, 838, 780 cm^-1. Anal. Calcd for C₁₁H₂₂O₂Si: C, 61.63; H, 10.34. Found: C, 61.58; H, 10.61.
(1 Z ,3 E )-1-(1-Ethoxyethoxy)-1,3-octadiene ( 2d) Pale yellow oil; purified by chromatography on silica gel (hexane-EtOAc = 70:1 to 40:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.39 (1 H, ddd, J = 15.4, 10.8, 1.4 Hz, 3-H), 6.12 (1 H, d, J = 5.9 Hz, 1-H), 5.57 (1 H, dt, J = 15.4, 7.0 Hz, 4-H), 5.12 (1 H, dd, J = 10.8, 5.9 Hz, 2-H), 4.94 (1 H, q, J = 5.4 Hz, OCHO), 3.74 (1 H, dq, J = 9.5, 7.2 Hz, OCH₂CH₃), 3.49 (1 H, dq, J = 9.5, 7.2 Hz, OCH₂CH₃), 2.12-2.04 (2 H, dt, J = 7.0, 6.8 Hz, 5-CH₂), 1.43-1.25 (4 H, m, 6-CH₂ and 7-CH₂), 1.39 [3 H, d, J = 5.4 Hz, OCH(CH₃)O], 1.21 (3 H, t, J = 7.2 Hz, OCH₂CH₃), 0.89 (3 H, t, J = 7.0 Hz, 8-CH₃). ¹³C NMR (68 MHz, CDCl₃): δ = 138.9, 131.5, 122.8, 108.1, 100.9, 62.5, 32.7, 31.8, 22.4, 20.6, 15.2, 14.0. IR (film): 3036, 2956, 2924, 2872, 1656, 1618, 1444, 1382, 1342, 1276, 1226, 1150, 1134, 1112, 1080, 1052, 974, 880, 830, 748 cm^-1. Anal. Calcd for C₁₂H₂₂O₂: C, 72.68; H, 11.18. Found: C, 72.52; H, 11.47.
(1 Z ,3 E )-1-(Methoxymethoxy)-1,3-octadiene ( 2e) Colorless oil; purified by chromatography on silica gel (hexane-EtOAc = 70:1 to 40:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.39 (1 H, ddd, J = 15.5, 10.9, 1.1 Hz, 3-H), 6.03 (1 H, d, J = 6.2 Hz, 1-H), 5.60 (1 H, dt, J = 15.5, 7.0 Hz, 4-H), 5.17 (1 H, dd, J = 10.9, 6.2 Hz, 2-H), 4.83 (2 H, s, OCH₂O), 3.42 (3 H, s, OCH₃), 2.16-2.02 (2 H, dt, J = 7.0, 6.8 Hz, 5-CH₂), 1.45-1.23 (4 H, m, 6-CH₂ and 7-CH₂), 0.90 (3 H, t, J = 7.0 Hz, 8-CH₃). ¹³C NMR (68 MHz, CDCl₃): δ = 141.2, 132.2, 122.4, 108.9, 96.4, 55.8, 32.7, 31.7, 22.4, 14.1. IR (film): 3036, 2952, 2920, 1658, 1618, 1464, 1386, 1306, 1242, 1160, 1114, 1042, 974, 924, 830, 750 cm^-1. Anal. Calcd for C₁₀H₁₈O₂: C, 70.55; H, 10.66. Found: C, 70.38; H, 10.75.
(1 Z ,3 E )-1-(Benzyloxymethoxy)-1,3-octadiene ( 2f) Colorless oil; purified by chromatography on silica gel (hexane-EtOAc = 80:1 to 50:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 7.37-7.27 (5 H, m, Ph), 6.40 (1 H, ddd, J = 15.4, 10.8, 1.1 Hz, 3-H), 6.10 (1 H, d, J = 6.2 Hz, 1-H), 5.61 (1 H, dt, J = 15.4, 7.0 Hz, 4-H), 5.19 (1 H, dd, J = 10.8, 6.2 Hz, 2-H), 4.95 (2 H, s, OCH₂O), 4.65 (2 H, s, OCH₂Ph), 2.16-2.06 (2 H, dt, J = 7.0, 6.8 Hz, 5-CH₂), 1.45-1.25 (4 H, m, 6-CH₂ and 7-CH₂), 0.90 (3 H, t, J = 7.0 Hz, 8-CH₃). ¹³C NMR (68 MHz, CDCl₃): δ = 141.2, 137.0, 132.2, 128.3, 128.0, 127.8, 122.4, 109.0, 94.3, 69.8, 32.7, 31.7, 22.4, 14.1. IR (film): 3032, 2952, 2924, 2868, 1658, 1618, 1496, 1454, 1380, 1300, 1226, 1172, 1116, 1042, 974, 904, 832, 744, 696 cm^-1. Anal. Calcd for C₁₆H₂₂O₂: C, 78.01; H, 9.00. Found: C, 78.16; H, 9.21.
(1 Z ,3 E )-1-(1-Methoxy-1-methylethoxy)-1,3-octadiene ( 2g) Pale yellow oil; purified by chromatography on silica gel (hexane-EtOAc = 80:1 to 60:1 as eluent). ¹H NMR (270 MHz, C₆D₆): δ = 6.83 (1 H, ddd, J = 15.5, 10.7, 1.1 Hz, 3-H), 6.32 (1 H, d, J = 6.2 Hz, 1-H), 5.61 (1 H, dt, J = 15.5, 7.0 Hz, 4-H), 5.30 (1 H, dd, J = 10.7, 6.2 Hz, 2-H), 3.01 (3 H, s, OCH₃), 2.13-2.01 (2 H, dt, J = 7.0, 6.5 Hz, 5-CH₂), 1.38-1.15 [10 H, m, OC(CH₃)₂O and 6, 7-CH₂], 0.81 (3 H, t, J = 7.0 Hz, 8-CH₃). ¹³C NMR (68 MHz, C₆D₆): δ = 137.0, 131.0, 124.2, 108.9, 101.9, 48.9, 33.2, 32.3, 25.0, 22.8, 14.3. IR (film): 3032, 2988, 2952, 2924, 2852, 1656, 1616, 1464, 1402, 1374, 1264, 1218, 1184, 1138, 1106, 1072, 1032, 974, 868, 782, 750 cm^-1. Anal. Calcd for C₁₂H₂₂O₂: C, 72.68; H, 11.18. Found: C, 72.55; H, 11.44.
(1 Z ,3 E )-1-(2-Tetrahydropyranyloxy)-1,3-octadiene ( 2h) Pale yellow oil; purified by chromatography on silica gel (hexane-EtOAc = 70:1 to 40:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.42 (1 H, ddd, J = 15.5, 10.9, 0.8 Hz, 3-H), 6.10 (1 H, d, J = 5.9 Hz, 1-H), 5.59 (1 H, dt, J = 15.5, 7.3 Hz, 4-H), 5.16 (1 H, dd, J = 10.9, 5.9 Hz, 2-H), 4.94 (1 H, t, J = 3.1 Hz, OCHO), 3.85 (1 H, ddd, J = 11.2, 9.5, 3.5 Hz, THP-6-CH₂), 3.62-3.52 (1 H, m, THP-6-CH₂), 2.16-2.04 (2 H, dt, J = 7.3, 6.8 Hz, 5-CH₂), 1.99-1.11 (10 H, m, THP-3,4,5-CH₂ and 6,7-CH₂), 0.90 (3 H, t, J = 7.3 Hz, 8-CH₃). ¹³C NMR (68 MHz, CDCl₃): δ = 140.8, 131.8, 122.6, 108.4, 98.5, 61.9, 32.7, 31.8, 29.7, 25.2, 22.4, 18.7, 14.1. IR (film): 3032, 2946, 2924, 2868, 1658, 1618, 1454, 1356, 1242, 1202, 1124, 1028, 970, 904, 872, 816, 750 cm^-1. Anal. Calcd for C₁₃H₂₂O₂: C, 74.24; H, 10.54. Found: C, 74.25; H, 10.78.
(1 Z ,3 E )-1-( tert -Butyldimethylsilyloxy)-6-methyl-1,3,5-heptatriene ( 2i) Colorless oil; purified by chromatography on silica gel (hexane-Et₂O = 50:1 to 20:1 as eluent). ¹H NMR (270 MHz, CDCl₃): δ = 6.48 (1 H, dd, J = 15.1, 10.5 Hz, 3-H), 6.30 (1 H, dd, J = 15.1, 10.8 Hz, 4-H), 6.17 (1 H, d, J = 5.7 Hz, 1-H), 5.93-5.86 (1 H, m, 5-H), 5.24 (1 H, dd, J = 10.5, 5.7 Hz, 2-H), 1.79 [3 H, s, C(CH₃)₂], 1.76 [3 H, s, C(CH₃)₂], 0.94 [9 H, s, SiC(CH₃)₃], 0.16 [6 H, s, Si(CH₃)₂]. ¹³C NMR (68 MHz, CDCl₃): δ = 139.5, 134.0, 125.9, 125.6, 123.2, 111.3, 26.2, 25.7, 18.4, -5.2. IR (film): 3028, 2952, 2924, 2856, 1646, 1628, 1584, 1470, 1408, 1274, 1256, 1236, 1140, 1066, 1032, 1006, 986, 964, 838, 780 cm^-1. Anal. Calcd for C₁₄H₂₆OSi: C, 70.52; H, 10.99. Found: C, 70.78; H, 11.23.

13

Use of s-BuLi or t-BuLi in Et₂O instead of n-BuLi gave the same results, which suggests that the aggregation states of n-BuLi under our reaction conditions are monomer or dimer, since t-BuLi becomes dimeric in Et₂O without substrates.

14

The complete 1Z-to-1E changeover was observed in the case of 1d. The reaction of silyl derivative 1b in THF under the same conditions gave a mixture of stereoisomers without any detectable retro-Brook rearrangement product:
(1Z,3E)/(1Z,3Z)/(1E,3E)/(1E,3Z) = 42:1:16:21 (yield, %).

15

Use of TMEDA-Et₂O instead of THF gave almost the same results.

16 Hartung J. Kneuer R. Eur. J. Org. Chem.  2000,  1677