E-Book, Englisch, 802 Seiten, PDF, Format (B × H): 170 mm x 240 mm
Reihe: Science of Synthesis
Compounds of Groups 13 and 2 (Al, Ga, In, Tl, Be...Ba)
E-Book, Englisch, 802 Seiten, PDF, Format (B × H): 170 mm x 240 mm
Reihe: Science of Synthesis
ISBN: 978-3-13-171771-9
Verlag: Thieme
Format: PDF
Kopierschutz: Adobe DRM (»Systemvoraussetzungen)
Science of Synthesis is a quality reference work developed by a highly esteemed editorial board to provide a comprehensive and critical selection of reliable organic and organometallic synthetic methods. This unique resource is designed to be the first point of reference when searching for a synthesis strategy.
- Contains the expertise of presently 400 leading chemists worldwide. - Critically evaluates the preparative applicability and significance of the synthetic methods. - Discusses relevant background information and provides detailed experimental procedures
For full information on the Science of Synthesis series, visit the Science of Synthesis Homepage
Series Editors: D. Bellus, S. V. Ley, R. Noyori, M. Regitz, E. Schaumann, I. Shinkai, E. J. Thomas, B. M. Trost, P. J. Reider
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Weitere Infos & Material
7.1 Product Class 1: Aluminum Compounds
7.1.1 Product Subclass 1: Zerovalent Aluminum and Its Alloys
7.1.2 Product Subclass 2: Aluminum Hydrides
7.1.3 Product Subclass 3: Aluminum Halides
7.1.4 Product Subclass 4: Aluminum Alkoxides and Phenoxides
7.1.5 Product Subclass 5: Aluminum Thiolates
7.1.6 Product Subclass 6: Aluminum Selenolates
7.1.7 Product Subclass 7: Aluminum Amides
7.1.8 Product Subclass 8: Aluminum Oxide (Alumina)
7.1.9 Product Subclass 9: Triorganoaluminum Compounds Involving Aluminum Alkyls, Alkenyls, Aryls, and Cyanides
7.2 Product Class 2: Gallium Compounds
7.3 Product Class 3: Indium Compounds
7.4 Product Class 4: Thallium Compounds
7.5 Product Class 5: Beryllium Compounds
7.6 Product Class 6: Magnesium Compounds
7.6.1 Product Subclass 1: Magnesium Metal
7.6.2 Product Subclass 2: Magnesium Hydride
7.6.3 Product Subclass 3: Magnesium–Metal Reagents
7.6.4 Product Subclass 4: Alkynyl Grignard Reagents
7.6.5 Product Subclass 5: Aryl Grignard Reagents
7.6.6 Product Subclass 6: Alkenyl Grignard Reagents
7.6.7 Product Subclass 7: Propargylic Grignard Reagents
7.6.8 Product Subclass 8: Benzylic Grignard Reagents
7.6.9 Product Subclass 9: Allylic Grignard Reagents
7.6.10 Product Subclass 10: Alkyl Grignard Reagents
7.6.11 Product Subclass 11: Grignard Reagents with Transition Metals
7.6.12 Product Subclass 12: Magnesium Halides
7.6.13 Product Subclass 13: Magnesium Oxide, Alkoxides, and Carboxylates
7.6.14 Product Subclass 14: Magnesium Amides
7.6.15 Product Subclass 15: Dialkyl- and Diarylmagnesiums
7.7 Product Class 7: Calcium Compounds
7.8 Product Class 8: Strontium Compounds
7.9 Product Class 9: Barium Compounds
7.1 Product Class 1: Aluminum Compounds
7.1.1 Product Subclass 1: Zerovalent Aluminum and Its Alloys
S. Saito General Introduction
Aluminum(0) is a typical one-electron-transfer agent, with a low first ionization potential of 5.986 eV, to give aluminum(III); this makes it one of the most reducing metals. This characteristic advantage is well featured, for example, not only in the reduction of several transition metals and organic molecules, but also in pinacol- or McMurry-type coupling. In addition, aluminum has the advantage of being readily available, inexpensive, stable, easy to handle, nontoxic, and resistant to water because it forms a thin film of insoluble alumina that protects against further reaction. Synthesis of Product Subclass 1
7.1.1.1 Method 1: Aluminum Treated with Mercury(II) Chloride
Reduction of mercury(II) chloride to mercury(0) with excess aluminum(0) gives aluminum amalgam,[1–5] which is a very useful reducing agent for many functional groups.[6] For example, sulfinyl and phosphorus ylide groups can be reduced by this reagent, presumably by electron transfer from mercury(0), and subsequent protonation gives the corresponding hydrocarbons. Aluminum amalgam is also used for the selective removal of sulfinyl and phosphorus ylide groups from ketones, for example, the conversion of methylsulfinyl ketone 1 into acetophenone (2) (? Scheme 1).[5] Aluminum amalgam is a shiny solid, which has been prepared by many different methods, and which generally reacts vigorously with water with liberation of hydrogen gas equivalent to the amount of aluminum present. It is therefore also used to dry organic solvents (e.g., diethyl ether, ethanol). It can be stored under dry diethyl ether. ? Scheme 1 Selective Removal of Sulfinyl and Phosphorus Ylide Groups from Ketones with Aluminum Amalgam[5] Aluminum Amalgam:[1,2] CAUTION: Mercury(II) chloride is a poison by ingestion and is toxic by skin contact. When heated to decomposition it emits toxic fumes of mercury. Al turnings (oil-free) were etched with dil NaOH to the point of rapid H2 evolution; the soln was then decanted, and the metal was superficially washed once with H2O so that some alkali was left behind. It was then treated with 0.5% aq HgCl2 for 1–2 min, and the entire process was repeated. The shiny amalgamated metal was washed rapidly in turn with H2O, EtOH, and Et2O and was used at once. This material reacted vigorously with H2O with liberation of H2 equivalent to the amount of Al present and could be used to dry Et2O or EtOH. Aluminum Amalgam:[3] CAUTION: Mercury(II) chloride is a poison by ingestion and is toxic by skin contact. When heated to decomposition it emits toxic fumes of mercury. A 25-mL flask was charged with Al chips (5 mm × 5 mm) cut from Al foil (360 mg, 13.3 mmol). A 2% aq soln of HgCl2 (15 mL) was added, the mixture was stirred by hand for 1 min, and then the aqueous phase was removed by a water-vacuum-aspirated pipet. The chips were washed successively with abs EtOH (5 × 20 mL), anhyd Et2O (5 × 15 mL), and dry THF (5 × 15 mL); the washings were removed each time by decantation. Fresh THF (20 mL) was added, and the mixture was ready for use in further reactions. Aluminum Trimethoxide Solution in Methanol:[4] CAUTION: Mercury(II) chloride is a poison by ingestion and is toxic by skin contact. When heated to decomposition it emits toxic fumes of mercury. A mixture of Al foil (2.70 g, 100 mmol), HgCl2 (51 mg, 0.19 mmol), and dry MeOH (50 mL) was refluxed until all the Al had dissolved to give a gray suspension. CCl4 (1 mL) (CAUTION: toxic), which acts as a catalyst, was added to the boiling mixture. After the mixture had cooled to rt, dry MeOH was added to adjust the volume of the soln to 100 mL, to give a 1M soln of Al(OMe)3 in MeOH. Acetophenone (2);Typical Procedure:[5] CAUTION: Mercury(II) chloride is a poison by ingestion and is toxic by skin contact. When heated to decomposition it emits toxic fumes of mercury. To prepare the Al/Hg amalgam, Al foil was cut into strips of approximately 10 cm × 1.0 cm, and these were immersed, all at once, into a 2% aq soln of HgCl2 for 15 s. After the strips had been rinsed with abs EtOH followed by Et2O, they were cut into 1.0 cm × 1.0 cm squares, directly into the reaction vessel. A mixture of methylsulfinyl ketone 1 (0.5 g, 2.75 mmol), the Al/Hg amalgam (28 mg), and aq THF (30 mL) was stirred at 0°C for 10 min. The mixture was then filtered, and the filtered solids were washed with THF. The filtrate was concentrated to remove most of the THF, Et2O was added, and the Et2O phase was separated from the aqueous phase. The Et2O soln was dried (Na2SO4) and concentrated; this left behind pure acetophenone (2); yield: 98%. 7.1.1.2 Method 2: Aluminum Treated with Potassium Hydroxide in Methanol
There are several methods in which aluminum(0) is used under strongly basic conditions in an alcoholic solvent. Typically, aromatic ketones, e.g. acetophenone, undergo pinacol coupling in the presence of aluminum powder, potassium hydroxide, and methanol (? Scheme 2).[5] A novel, rapid, one-pot procedure for the reductive coupling of aldimines (e.g., 3) has been described, in which the inexpensive reagents aluminum powder and potassium hydroxide are used (? Scheme 2).[7,8] The vicinal diamines (e.g., 4) are generally obtained in excellent yields without the formation of side products. However, the rac selectivity is consistently found to be only moderate [(rac/meso) 60:40 to 85:15]. ? Scheme 2 Pinacol Coupling of an Aromatic Ketone or Imine Promoted by Aluminum with Potassium Hydroxide[5,7,8] N,N', 1, 2-tetraphenylethane-1, 2-diamine (4);Typical Procedure:[7,8] Benzylideneaniline (3; 1.8 g, 10 mmol) was dissolved in MeOH (10 mL). Al powder (0.27 g, 10 mmol) and KOH (1.7 g, 30 mmol) were added, and the mixture was stirred at rt. The reaction became vigorous immediately after the addition of KOH. After 10 min, the mixture was filtered to remove the Al powder, and H2O (40 mL) was added to the filtrate. The filtrate was then extracted with CHCl3 (3 × 20 mL), and the soln was dried (Na2SO4) and concentrated under reduced pressure; N,N', 1, 2-tetraphenylethane-1, 2-diamine (4) was obtained as a mixture of diastereomers [(rac/meso) 7:3]; yield: 90%. 7.1.1.3 Method 3: Aluminum as Reductant for Titanium(IV) Chloride
Aluminum metal is a good reducing agent for titanium(IV) chloride, and attempts to use a catalytic amount of low-valent titanium have proved successful. In combination with aluminum metal, titanium can be used catalytically to effect Barbier-type allylation of imines (? Scheme 3).[9] In the absence of titanium(IV) chloride, the reaction does not occur at all. The aluminum(III) salts that accumulate in the medium function as a Lewis acid to form iminium ions, which, in turn, undergo allylation, leading to homoallylamines, e.g. 5. The course of the reaction depends considerably on the titanium/aluminum ratio. For example, titanium/aluminum ratios of 3:1 and 3:2 (to 1 equivaldimine), formally corresponding to one- and two-electron reductions, provide suspensions of different colors: green [possibly due to Ti(III)] and blue [possibly due to Ti(II)]. Neither of the reagents on its own give coupling products, whereas titanium/aluminum ratios of 1:1 and 3:4 result in yields of 29 and 38%, respectively. The benzaldimine derived from L-valine undergoes an asymmetric version of this process. ? Scheme 3 Allylation of an Imine Catalyzed by a Low-Valent Titanium Reagent Generated from Titanium(IV) by Reduction by Aluminum[9] Benzyl(1-phenylbut-3-enyl)amine (5);Typical Procedure:[9] Into a mixture of N-benzylbenzylideneamine (0.195 g, 1 mmol) and finely cut Al foil (0.027 g, 1 mmol) in dry THF (4 mL) were successively added allyl bromide (0.27 mL, 3 mmol) and TiCl4 (5.4 mL, 0.05 mmol) at rt. After being stirred for 8 h, the mixture was poured into 5% aq NaOH, worked up, and purified by column chromatography [silica gel, hexane/benzene (CAUTION: carcinogen)]; yield: 0.17 g (83%). 7.1.1.4 Method 4: Aluminum–Lead System
An aluminum–lead bimetallic system can be used to carry out reductive addition of carbon tetrachloride, carbon tetrabromide, bromotrichloromethane, trichloroacetamide, or trichloroacetonitrile to aldehydes (? Scheme 4).[10] It is noteworthy that commercially available lead powder (>99.9% pure) alone is not effective at all for this reductive addition. This suggests that lead(0), freshly generated on the aluminum surface, is important for the coupling reaction. For example, in the presence of 1.2 equivalents of aluminum and catalytic lead(II) bromide (Al/PbBr2 12:1), 2, 2, 2-trichloro-1-(4-chlorophenyl)ethanol (6) is prepared in 94% yield from...
