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70 Science of Synthesis 1.1 Organometallic Complexes of Nickel Scheme 67 Tail-to-Tail Dimerization of Methyl Acrylate [5] MeO2C MeO 2C MeO 2C Ni PMe + 3 CO 2Me MeO2C MeO 2C MeO 2C MeO 2C Ni PMe + 3 CO 2Me MeO 2C MeO2C H + PMe3 Ni CO 2Me CO2Me RajanBabu has developed an asymmetric protocol for the heterodimerization of vinylarenes and ethene. [159] The use of Hayashi s novel, weakly chelating phosphine 91 is critical to the success of this asymmetric reaction (Scheme 68). 1,6-Dienes (e.g., 92) also undergo direct cycloisomerization in the presence of bis[allyl(bromo)nickel] to afford methylenecyclopentane products (e.g., 93; Scheme 69). The scope of the intramolecular process allows preparation of a variety of carbocyclic and heterocyclic ring systems. A reaction mechanism involving in situ generation of a nickel hydride catalyst, alkene hydrometalation, cyclization, and â-hydride elimination has been proposed. [160] Scheme 68 Asymmetric Hydrovinylation of Alkenes [159] H Ar 1 L ∗ = R 1 = Me, Bn + 91 OR 1 PPh2 [NiBr(H2C CHCH 2)] 2, NaBAr 4, L ∗ Scheme 69 Cycloisomerization of Dienes [160] R 1 R 1 92 Ar 1 O O [NiBr(H 2C CHCH 2)] 2, R 1 3P [NiHL n] + R 1 R 1 81% NiL n + R 1 R 1 NiL n + − [NiHLn] + 92% R 1 R 1 93
1.1.4 Nickel–Alkene Complexes 71 [5,5¢-Bi(bicyclo[2.2.1]hept-2-en)-6-yl-kC 6 -6¢-olato-kO](2,2¢-bipyridyl-k 2 N 1 ,N 1 ¢)nickel (84): [153] A sample of 83 (0.35 g, 0.94 mmol) and benzene (10 mL) were placed in a round-bottomed flask attached to a swivel-frit assembly. The soln was stirred under N 2O (1 atm) at 55 8C for 3 d, after which the soln was filtered and the filtrate was taken to dryness under vacuum. The resulting solid was washed with petroleum ether (3 ” 5 mL), and the blue product was collected on a filter frit to give microcrystalline 84; yield: 0.16 g (44%). exo-trans-endo-3-Oxapentacyclo[9.2.1.1 5,8 .0 2,10 .0 4,9 ]pentadeca-6,12-diene (85): [153] A sample of 84 (0.12 g, 0.31 mmol) and benzene (10 mL) were placed in a round-bottomed flask, to which I 2 (0.08g, 0.31 mmol) was added under an argon counterflow. There was an immediate color change from blue to brown. The soln was stirred for 30 min at rt and filtered, and the filtrate was evaporated using a rotary evaporator. The residue was chromatographed (silica gel, hexane/EtOAc 100:3) to give 85 as a colorless oil; yield: 0.03 g (47%). (1R*,2S*,3R*,5R*)-2-Benzoyl-3-phenylbicyclo[3.3.0]octane-3-ol (90, R 1 = Ph); Typical Procedure: [131] A mixture of 2.44 M BuLi in hexane (0.43 mL, 1.05 mmol) and 1.0 M ZnCl 2 in Et 2O (0.70 mL, 0.70 mmol) in THF (5 mL) was stirred for 1 h at 08C. A soln of [Ni(cod) 2] (2; 3mg, 0.01 mmol) in THF (2 mL) was added by syringe, and the resulting soln was immediately transferred by cannula to a soln of 89 (91 mg, 0.30 mmol) in THF (3 mL) at 08C. After stirring for 1.5 h at 0 8C the deep red mixture was quenched with sat. NaHCO 3 (20 mL), extracted with EtOAc (3 ” 25 mL), dried (Na 2SO 4), filtered, and concentrated. The residue was chromatographed (silica gel, Et 2O/pentane 1:15) to afford 90 (R 1 = Ph) as a white crystalline solid; yield: 56 mg (60%). Dimethyl 3-Methyl-4-methylenecyclopentane-1,1-dicarboxylate (93,R 1 =CO 2Me); Typical Procedure: [160] The catalyst precursor was prepared as follows. To a soln of [{Ni(allyl)Br} 2] (4.2 mg, 0.012 mmol, 2.5 mol%, 0.05 equiv in Ni) in CH 2Cl 2 (1 mL) was added tris(4-methoxyphenyl)phosphine (8.5 mg, 0.024 mmol) in CH 2Cl 2 (1 mL). The mixture was stirred for 30 min, after which AgOTf (6 mg, 0.024 mmol) was added in one lot. After 30 min of stirring, a precipitate was formed (AgBr), which was subsequently removed by filtration through a pipet containing a plug of Celite. The catalyst was cooled to –348C and introduced into a soln of 92 (100 mg, 0.47 mmol) in CH 2Cl 2 (2 mL) at rt. The soln was stirred at rt for 2 h, after which the reaction was stopped and the mixture was concentrated. Analysis of the crude product showed it to be 92% of the expected product 93 and 8% starting material. The crude product was chromatographed on a column (silica gel, hexane/Et 2O 9:1) to afford pure 93 (R 1 =CO 2Me); yield: 92 mg (92%). 1.1.4.4 Method 4: Alkene Carbonylation The carbonylation of alkenes proceeds readily upon treatment of an alkene with a nickel catalyst in the presence of carbon monoxide and an alcohol or water (Scheme 70). [7,11,104] Tetracarbonylnickel(0) is the most comm<strong>only</strong> used nickel catalyst, although it is highly toxic. [188] This process is very useful for the carbonylation of simple alkenes such as ethene, but it has seen little use with complex organic molecules. Scheme 70 Carbonylation of Alkenes [104] H 2C CH 2 + CO + H 2O Ni CO 2H for references see p 79
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Science of Synthesis Houben-Weyl Me
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Science of Synthesis Houben-Weyl Me
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8 Science of Synthesis Category 1:
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Volume 1: Compounds withTransition
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Table of Contents Volume 2 13 Volum
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Table of Contents 15 Volume 4: Comp
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Table of Contents 17 4.4.27 Product
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Page 37 and 38: 1.1.2 Nickel-Allyl Complexes 37 tra
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Page 79 and 80: References 79 References [1] Chetcu
Page 81 and 82: References 81 [98] Tsuda, T.; Mizun
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Page 86 and 87: 86 Biographical Sketches Rinaldo Po
Page 88 and 89: 88 2.6.4.2.2 Variation 2: Two-Elect
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Page 92 and 93: 92 Science of Synthesis 2.6 Complex
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120 Science of Synthesis 2.6 Comple
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141 Science of Synthesis Houben-Wey
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4.4.27 Product Subclass 27: Æ-Halo
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4.4.27 Æ-Haloalkylsilanes 147 Sche
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4.4.27 Æ-Haloalkylsilanes 149 dros
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4.4.27 Æ-Haloalkylsilanes 151 4.4.
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4.4.27 Æ-Haloalkylsilanes 153 In g
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4.4.27 Æ-Haloalkylsilanes 155 4.4.
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4.4.27 Æ-Haloalkylsilanes 157 Æ-H
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References 159 References [1] Haman
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References 161 [93] Bruno, J. W.; S
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166 Biographical Sketches Alan Spiv
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168 5.1.22 Product Subclass 22: Ary
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170 Science of Synthesis 5.1 German
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176 References [43] Eaborn, C.; Var
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178 Abbreviations Chemical (cont.)
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180 Abbreviations Ligands (cont.) 2
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182 Abbreviations General (cont.) q
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