Reduction of Olefins Using Ruthenium Carbene Catalysts and Silanes

Abstract

Ruthenium carbene complexes are able to mediate reduction of olefins in the presence of trialkylsilanes. Under these ­reduction conditions, when kinetically favorable ring-closing ­metathesis is possible, a one-pot cyclization-reduction sequence can be performed.

Key words

reduction - hydrosilylation - stereoselective synthesis

References

• References for selected reviews see:
• 1a Trnka TM. Acc. Chem. Res.  2001,  34:  18 
• 1b Fürstner A. Angew. Chem. Int. Ed.  2000,  39:  3012 
• 1c Buchmeiser MR. Chem. Rev.  2000,  100:  1565 
• 1d Schuster M. Blechert S. Angew. Chem., Int. Ed. Engl.  1997,  36:  2036 
• 1e Deiters A. Martin SF. Chem. Rev.  2004,  104:  2199 
• 1f Giessert AJ. Diver ST. Chem. Rev.  2004,  104:  1317 
• 1g Poulsen CS. Madsen R. Synthesis  2003,  1 
• 1h Mori M. In Handbook of Metathesis   Vol. 2:  Grubbs RH. Wiley-VCH; Weinheim: 2003.  p.176 
• 1i Connon SJ. Blechert S. Angew. Chem. Int. Ed.  2003,  42:  1900 
• 1j Schrock RR. Hoveyda AH. Angew. Chem. Int. Ed.  2003,  42:  4592 
• 1k Fürstner A. Angew. Chem. Int. Ed.  2000,  39:  3013 
• 1l Grubbs RH. Chang S. Tetrahedron  1998,  54:  4413 
• 1m Astruc D. New J. Chem.  2005,  29:  42 
• 2a Alcaide B. Almendros P. Chem.-Eur. J.  2003,  9:  1259 
• 2b For non-metathetic transformations of organic substrates catalyzed by various ruthenium complexes, see: Trost BM. Toste D. Pinkerton AB. Chem. Rev.  2001,  101:  2067 
• 2c See also: Ajamian A. Gleason JL. Angew. Chem. Int. Ed.  2004,  43:  3754 
• 2d

  Review on the interface of ruthenium-carbene and ruthenium-hydride chemistry:

• 2e Schmidt B. Eur. J. Org. Chem.  2004,  1865 
• 3 Tallarico JA. Malnick LA. Snapper ML. J. Org. Chem.  1999,  64:  344 
• 4 Peppers BP. Diver ST. J. Am. Chem. Soc.  2004,  126:  9524 
• 5a Mori M. Saito N. Tanaka D. Takimoto M. Sato Y. J. Am. Chem. Soc.  2003,  125:  5606 
• 5b Quayle P. Fengas D. Richards S. Synlett  2003,  1797 
• For other non-metathetic activities of Ru carbene complexes see:
• 5c Schmidt B. Angew. Chem. Int. Ed.  2003,  42:  4996 
• 5d Faulkner J. Edlin CD. Fengas D. Preece I. Quayle P. Richards SN. Tetrahedron Lett.  2005,  46:  2381 
• 5e Edlin CD. Faulkner J. Fengas D. Knight CK. Parker J. Preece I. Quayle P. Richards SN. Synlett  2005,  572 
• 6 Lopez F. Delgado A. Rodriguez JR. Castedo L. Mascarenas JL. J. Am. Chem. Soc.  2004,  126:  10262 
• 7a Alcaide B. Almendros P. Alonso JM. Aly MF. Org. Lett.  2001,  3:  3781 
• 7b Cadot C. Dalko PI. Cossy J. Tetrahedron Lett.  2002,  43:  1839 
• 7c Sutton AE. Seigal BA. Finnegan DF. Snapper ML. J. Am. Chem. Soc.  2002,  124:  13390 
• 7d Wipf P. Rector SR. Takahashi H. J. Am. Chem. Soc.  2002,  124:  14848 
• 7e Schmidt B. J. Org. Chem.  2004,  69:  7672 
• 7f Le Notre J. Touzani R. Lavastre O. Bruneau C. Dixneuf PH. Adv. Synth. Catal.  2005,  347:  783 
• 7g Bressy C. Menant C. Piva O. Synlett  2005,  577 
• 8a Maifeld SV. Miller RL. Lee D. Tetrahedron Lett.  2002,  43:  6363 
• Hydrosilylation of alkynes:
• 8b Aricó CS. Cox LR. Org. Biomol. Chem.  2004,  2:  2558 
• 8c Maifeld SV. Tran MN. Lee D. Tetrahedron Lett.  2005,  46:  105 
• 9a Louie J. Bielawski CW. Grubbs RH. J. Am. Chem. Soc.  2001,  123:  11312 
• 9b Cossy J. Bargiggia F. BouzBouz S. Org. Lett.  2003,  5:  459 
• 10 For the use of silanes in selective reduction of olefins see: Jurkauskas V. Sadighi JP. Buchwald SL. Org. Lett.  2003,  5:  2417  and references cited therein
• Selected conjugate reductions using metal catalysts:
• 13a Mahoney WS. Stryker JM. J. Am. Chem. Soc.  1989,  111:  8818 
• 13b Lipshutz BH. Keith J. Papa P. Vivian R. Tetrahedron Lett.  1998,  39:  4627 
• 13c Mori A. Fujita A. Kajiro H. Nishihara Y. Hiyama T. Tetrahedron  1999,  55:  4573 
• 13d Chiu P. Szeto C.-P. Geng Z. Cheng K.-F. Org. Lett.  2001,  3:  1901 
• 13e Lipshutz BH. Papa P. Angew. Chem. Int. Ed.  2002,  41:  4580 
• 13f Ito H. Ishizuka T. Arimoto K. Miura K. Hosomi A. Tetrahedron Lett.  1997,  38:  8887 
• 15 The relative stereochemistry of the major isomers was attributed on the basis of the J values observed in the ¹H NMR spectra. Moreover, 28 was transformed to the known β-hydroxy ester (TBAF, overnight), and the spectral data of the desilylated compound was compared with the literature data: Bouzide A. Org. Lett.  2002,  4:  1347 

11

Product ratio was determined by GC-MS.

12

2,6-Dimethyl-8-triethylsilyloxyundec-2,6-diene (20).
To a solution of olefin 15 (200 mg, 1.03 mmol, 1 equiv) in degassed CH₂Cl₂ (2 mL) were added the silane reagent (0.65 mL, 4.12 mmol, 4 equiv) and catalyst 1 (21 mg, 25.7 µmol, 2.5 mol%) at r.t. The reaction was stirred at reflux until total conversion of the starting material. The solution was concentrated under reduced pressure, and the crude product was purified by flash chromatography on silica gel using a gradient of eluent (pentane-EtOAc). Colorless oil (200 mg, 0.65 mmol, 63%); R _f = 0 .57 (pentane-EtOAc, 95:1). IR (neat): 1475, 1400, 1260, 1080, 760 cm^-1. ¹H NMR (300 MHz, CDCl₃, E- and Z-isomers): δ = 5.10-5.00 (m, 2 H), 4.30-4.20 (m, 1 H), 2.05-1.89 (m, 4 H), 1.61 (dd, J = 4.9, 1.1 Hz, 3 H), 1.54 (dd, J = 4.5, 1.5 Hz, 6 H), 1.35-1.15 (m, 4 H), 0.87 (t, J = 7.9 Hz, 9 H), 0.84 (t, J = 6.4 Hz, 3 H), 0.49 (q, J = 7.5 Hz, 6 H). ¹³C NMR (75 MHz, CDCl₃): E-isomer δ = 134.4, 131.4, 129.5, 124.1, 69.3, 40.9, 39.6, 26.3, 25.6, 18.6, 17.5, 16.4, 14.1, 6.8, 5.0. Z-Isomer: δ = 134.6, 131.7, 130.3, 124.1, 68.9, 41.2, 32.4, 26.5, 23.4, 18.8, 17.6, 16.4, 14.1, 6.8, 4.9. MS (EI, 70 eV): E-isomer m/z (%) = 310 (8) [M⁺], 267 (100), 173 (24), 75 (39), 69 (40). MS (EI, 70 eV): Z-isomer m/z (%) = 310 (20) [M⁺], 267 (25), 173 (97), 135 (59), 115 (38), 107 (32), 103 (100), 75 (54), 69 (45).

14

4-(4-Methoxyphenyl)butan-2-one (25).
To a solution of compound 21 (42 mg, 0.24 mmol, 1 equiv) in degassed CH₂Cl₂ (0.5 mL) at r.t. were added triethylsilane (0.10 mL, 0.70 mmol, 2.5 equiv) and catalyst 1 (5 mg, 7 mol, 2.5 mol%). The resulting solution was stirred until total conversion of the starting material. The solution was concentrated under reduced pressure, and the crude product was purified by flash chromatography on silica gel using a gradient of eluent (pentane-EtOAc). Colorless oil (30 mg, 0.17 mmol, 70%); R _f = 0.63 (pentane-EtOAc, 4:1). IR (neat): 1720, 1610, 1510, 1250, 1035 cm^-1. ¹H NMR (300 MHz, CDCl₃): δ = 7.05 (d, J = 8.7 Hz, 2 H), 6.75 (d, J = 8.7 Hz, 2 H), 3.70 (s, 3 H), 2.70 (m, 4 H), 2.05 (s, 3 H). ¹³C NMR (75 MHz, CDCl₃): δ = 208.0, 157.8, 132.9, 129.1, 113.8, 55.1, 45.3, 29.9, 28.7. MS (EI, 70 eV): m/z (%) = 178 (39) [M⁺], 121 (100).

16

As one of our referees pointed out, it is likely that hydrogenation occurred by the metathesis-inactive catalyst after the RCM reaction was completed, because the RCM was much faster than the modification of carbene catalyst by silanes or hydrogen, generated from dimerization of silanes.