Construction of Terminal Conjugated Enynes: Regio- and Stereoselective Syntheses of 3-Alken-1-ynes and 1-Trimethylsilyl-3-alken-1-ynes from Alkenyldialkylboranes and (Trimethylsilyl)ethynyl Bromide

Abstract

The cross-coupling reaction of (E)- and (Z)-1-alkenyldialkylboranes with (trimethylsilyl)ethynyl bromide proceeds in the presence of a base and a catalytic amount of Cu(acac)₂ under very mild conditions to provide conjugated enynes whose carbon-carbon triple bond is in distal position. The use of 1 M NaOMe as a base exclusively affords both (E)- and (Z)-3-alken-1-ynes with high regio- and stereoselectivity, while the use of LiOH·H₂O instead of 1 M NaOMe preferentially gives both (E)- and (Z)-1-trimethylsilyl-3-alken-1-ynes regio- and stereoselectively.

cross-coupling - 3-alken-1-yne - 1-trimethylsilyl-3-alken-1-yne - alkenyldialkylborane - (trimethylsilyl)ethynyl bromide

References

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2a Stille JK. Simpson H. J. Am. Chem. Soc.  1987,  109:  2138 

2b Cabezas JA. Oehlschlager AC. Synthesis  1999,  107 

3 For example, see: Tsushima K. Murai A. Tetrahedron Lett.  1992,  33:  4345 ; and references therein

4 For example, see: Kobayashi S. Reddy R. Sugiura Y. Sasaki D. Miyagawa N. Hirama M. J. Am. Chem. Soc.  2001,  123:  2887 ; and references therein

For the cross-coupling reaction of organocopper, see:

5a Normant JF. Commercon A. Villieras J. Tetrahedron Lett.  1975,  16:  1465 

5b Commercon A. Normant JF. Villieras J. Tetrahedron  1980,  36:  1215 

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6a Palmisano G. Santagostino M. Synlett  1993,  771 

6b Palmisano G. Santagostino M. Tetrahedron  1993,  49:  2533 

6c Palmisano G. Santagostino M. Helv. Chim. Acta  1993,  76:  2356 

6d Untiedt S. de Meijere A. Chem. Ber.  1994,  127:  1511 

6e Suzenet F. Parrain J.-L. Quintard J.-P. Eur. J. Org. Chem.  1999,  2957 

6f Siegel K. Brückner R. Synlett  1999,  1227 

For the cross-coupling reaction of organozirconium, see:

7a Kasai K. Liu Y. Hara R. Takahashi T. Chem. Commun.  1998,  1989 

7b Liu Y. Xi C. Hara R. Nakajima K. Yamazaki A. Kotora M. Takahashi T. J. Org. Chem.  2000,  65:  6951 

7c For Heck reaction, see: Jeffery T. Synthesis  1987,  70 

For example, see:

8a Miyaura N. Suzuki A. Chem. Rev.  1995,  95:  2457 

8b Suzuki A. In Metal-Catalyzed Cross-coupling Reactions   Diederich F. Stang PJ. Wiley-VCH; Weinheim: 1998. 

8c Suzuki A. J. Organomet. Chem.  1999,  576:  147 

9

To a stirred solution of (E)-1-octenylbis(1,2-dimethyl-propyl)borane (4 mmol) in THF (12 mL) at -15 °C, Cu(acac)₂ (0.052 g, 0.2 mmol) was added under an argon flow. (Trimethylsilyl)ethynyl bromide (0.474 g, 2.68 mmol) and 1 M NaOMe (4 mL, 4 mmol) were then added dropwise to the solution, and the resulting mixture was allowed to warm gradually to room temperature and to stir overnight. The reaction mixture was treated with 3 M NaOH (4 mL) and 30% H₂O₂ (2 mL) at 0 °C and stirred for 1 h at the same temperature to decompose the residual organoboron compound. The resultant mixture was extracted with ether, washed with brine, and dried over anhydrous Na₂SO₄. The solvent was removed on a rotary evaporator under reduced pressure, and the crude product was purified by column chromatography on silica gel, with n-pentane as eluent, to give product 2a (0.255 g, 70% yield) as a colorless liquid. Compound 2a: ¹H NMR (CDCl₃) δ: 0.88 (t, 3 H), 1.1-1.5 (m, 8 H), 2.0-2.2 (m, 2 H), 2.76 (dd, J = 2.2, 0.4 Hz, 1 H), 5.47 (ddt, J = 16.0, 2.2, 1.5 Hz, 1 H), 6.22 (dtd, J = 16.0, 6.8, 0.4 Hz, 1 H); ¹³C NMR (CDCl₃) δ: 14.04, 22.60, 28.58, 28.79, 31.68, 33.02, 75.49 (CH), 82.66 (C-), 108.52
(CH-), 146.96 (=CH-); IR(neat) 3315, 3024, 2956, 2927, 2856, 2104, 1629, 1465, 1436, 954, cm^-1; HRMS (EI) C₁₀H₁₆: requires 136.1252; found 136.1254.

10

To a stirred solution of (E)-1-octenyldicyclohexylborane (4 mmol) in THF (12 mL) at -15 °C, Cu(acac)₂ (0.052 g, 0.2 mmol) was added under an argon flow. (Trimethyl-silyl)ethynyl bromide (0.474 g, 2.68 mmol) was added dropwise to the solution, and then LiOH·H₂O (0.168 g, 4 mmol) was introduced into the solution under an argon flow. The resulting mixture was allowed to warm gradually to room temperature and to stir overnight. After the reaction mixture was neutralized with sat. NH₄Cl, the resultant mixture was treated with NaBO₃·4H₂O (1.846 g, 12 mmol) and H₂O (4 mL) at room temperature with vigorous stirring for 2 h to decompose the residual organoboron compound. Workup is the same as described in ref. 9. The crude product was purified by column chromatography on silica gel, with n-pentane as eluent, to give product 3a (0.401 g, 72% yield) as a colorless liquid. Compound 3a: ¹H NMR (CDCl₃) δ: 0.17 (s, 9 H), 0.88 (t, 3 H), 1.1-1.5 (m, 8 H), 2.0-2.2 (m, 2 H), 5.52 (dt, J = 15.8, 1.5 Hz, 1 H), 6.20 (dt, J = 15.8, 6.8 Hz, 1 H); ¹³C NMR (CDCl₃) δ 0.00 (Me × 3), 14.00, 22.55, 28.58, 28.78, 31.63, 33.06, 92.43 (C-), 104.28 (C-), 109.61 (=CH-), 146.26 (=CH-); IR(neat) 2958, 2927, 2856, 2175, 2133, 1249, 1085, 952, 842, 759 cm^-1; HRMS (EI) C₁₃H₂₄Si: requires 208.1647, found 208.1664.

11 Negishi E. Williams RM. Lew G. Yoshida T. J. Organomet. Chem.  1975,  92:  C4 

12

(Z)-3-Decen-1-yne(5a): ¹H NMR (CDCl₃) δ: 0.88 (t, 3 H), 1.1-1.55 (m, 8 H), 2.2-2.45 (m, 2 H), 3.05 (d, J = 2.2 Hz, 1 H), 5.45 (ddt, J = 11.0, 1.3, 0.9 Hz, 1 H), 5.98 (dtd, J = 11.0, 7.3, 0.9 Hz, 1 H); ¹³C NMR (CDCl₃) δ: 14.04, 22.60, 28.74, 28.87, 30.29, 31.68, 80.62 (C-), 81.11 (CH), 108.03 (=CH-), 146.22 (=CH-); IR(neat) 3313, 3024, 2956, 2927, 2856, 2358, 1465, 738 cm^-1; HRMS (EI) C₁₀H₁₆: requires 136.1252, found 136.1253.

13

(Z)-1-Trimethylsilyl-3-decen-1-yne(6a): ¹H NMR (CDCl₃) δ: 0.19 (s, 9 H), 0.88 (t, 3 H), 1.1-1.55 (m, 8 H), 2.2-2.45 (m, 2 H), 5.48 (dt, J = 11.0, 1.3 Hz, 1 H), 5.94 (dt, J = 11.0, 7.3 Hz, 1 H); ¹³C NMR (CDCl₃) δ: 0.00 (Me × 3), 14.00, 22.59, 28.66, 28.78, 30.25, 31.59, 98.41 (C-), 102.24 (C-), 109.16 (=CH-), 145.57 (=CH-); IR(neat) 3020, 2958, 2927, 2856, 2148, 1249, 842, 759 cm^-1; HRMS (EI) C₁₃H₂₄Si: requires 208.1647, found 208.1671.

14a Allred GD. Liebeskind LS. J. Am. Chem. Soc.  1996,  118:  2748 

14b Zhang S. Zhang D. Liebeskind LS. J. Org. Chem.  1997,  62:  2312 

15 Evans DA. Katz JL. West TR. Tetrahedron Lett.  1998,  39:  2937 

16 For example, see: Sonogashira K. In Metal-Catalyzed Cross-coupling Reactions   Diederich F. Stang PJ. Wiley-VCH; Weinheim: 1998. 

17 Mori A. Shimada T. Kondo T. Sekiguchi A. Synlett  2001,  649 

18

(E)-1-Phenyl-3-decen-1-yne: ¹H NMR (CDCl₃) δ: 0.88 (t, 3 H), 1.1-1.5 (m, 8 H), 2.05-2.3 (m, 2 H), 5.70 (dt, J = 15.8, 1.4 Hz, 1 H), 6.22 (dt, J = 15.8, 7.0 Hz, 1 H), 7.2-7.5 (m, 5 H); ¹³C NMR (CDCl₃) δ: 14.04, 22.60, 28.79(-CH₂- × 2), 31.68, 33.22, 87.91 (C-), 88.44 (C-), 109.57 (=CH-), 123.79 (=C<), 127.82 (=CH-), 128.22 (=CH- × 2), 131.44 (=CH- × 2), 145.16 (=CH-); IR (neat) 3080, 3055, 3020, 2954, 2927, 2854, 2202, 1596, 1571, 1488, 1463, 1454, 1442, 1379, 1303, 1068, 952, 912, 754, 690 cm^-1; MS (EI) m/z 212 (M⁺, 51%), 183(3), 169(6), 155(24), 141(78), 128(100), 115(41), 102(6), 91(13), 77(7), 63(4). (Z)-1-Phenyl-3-decen-1-yne: ¹H NMR (CDCl₃) δ: 0.88 (t, 3 H), 1.1-1.5 (m, 8 H), 2.25-2.55 (m, 2 H), 5.67 (dt, J = 10.8, 1.1 Hz, 1 H), 5.96 (dt, J = 10.8, 7.0 Hz, 1 H), 7.2-7.5 (m, 5 H); ¹³C NMR (CDCl₃) δ: 14.08, 22.64, 28.87(-CH₂- × 2), 30.41, 31.72, 86.57 (C-), 93.45 (C-), 109.05 (=CH-), 123.87 (=C<), 127.94 (=CH-), 128.27 (=CH- × 2), 131.40 (=CH- × 2), 144.31 (=CH-); IR (neat) 3080, 3058, 3020, 2956, 2927, 2856, 1595, 1571, 1488, 1467, 1456, 1440, 1398, 1377, 1068, 1028, 1014, 912, 754, 732, 690 cm^-1; HRMS (EI) C₁₆H₂₀: requires 212.1565, found 212.1559.