Allylsilanes

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Scheme 30 Allylsilanes by Palladium(0)-Catalyzed Carbosilylation of Allenes [134] R 1 I + Bu3Sn SiMe3 + FOR PERSONAL USE ONLY 858 Science of Synthesis 4.4 Silicon Compounds R 2 R 3 Pd(dba)2 toluene R1 = H; R2 = R3 = Me 85% R1 = 2-OMe; R2 = R3 = Me 83% R1 = 4-Ac; R2 = H; R3 = Cy 80%; (E/Z) 92:8 Allylsilanes 65; General Procedure: [134] A 50-mL flask containing Pd(dba) 2 (0.0287 g, 0.05 mmol) was purged with N 2 (3 ”). Toluene (3 mL), the organic halide (1.00 mmol), the allene (2.00 mmol), and Bu 3SnSiMe 3 (360 mg, 1 mmol) were then added bysyringe to the flask. The mixture was heated with stirring at 808C for 7 h. The soln changed color rapidlyfrom purple-red to pale yellow in the first few min and maintained the same color for the rest of the reaction. As the reaction approached completion, a black precipitate of Pd(0) appeared graduallyon the wall of the flask. At the end of the reaction, the soln was filtered through Celite. The filtrate was concentrated, and the residue was purified bycolumn chromatography(silica gel, hexane). Trimethyl(3-methyl-2-phenylbut-2-enyl)silane (65, R 1 =H;R 2 =R 3 = Me); yield: 85%. [2-(2-Methoxyphenyl)-3-methylbut-2-enyl]trimethylsilane (65, R 1 = 2-OMe; R 2 =R 3 = Me); yield: 83%. 4.4.40.18 Method 18: From Lithium Allyl Alcoholates and Hexamethyldisilane A direct synthesis of terminally substituted allylsilanes from allyl alcohols involves the generation of lithium allyl alcoholates with methyllithium and follow-up treatment with hexamethyldisilane in hexamethylphosphoric triamide. For example, both allyl alcohols 66 and 67 give mixtures of the E- and Z-allylsilanes 11, in which the E-isomer predominates (Scheme 31). [135] Apart from allyl alcohols, carbonyl compounds can also be used as precursors to lithium allyl alcoholates; the latter are generated in situ by 1,2-addition of vinyllithium to saturated carbonyl compounds, or by addition of alkyllithium to á,â-unsaturated carbonyl compounds. This one-pot reaction occurs presumably by counterattack of the trimethylsilyl anion, generated by the reaction of alkoxide and hexamethyldisilane, on the silyl ether intermediate. This method does not work for the preparation of cyclic allylsilanes from cyclic allyl alcohols, such as cyclohex-2-en-1-ol. Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG R 2 R 3 65 R 1 SiMe3
Scheme 31 Allylsilanes from Allyl Alcoholates and Hexamethyldisilane [135] 66 67 OH 1. MeLi, Et2O 2. 80 o Me3Si SiMe3, HMPA C, 24 h 72%; (E/Z) 3:1 OH 1. MeLi, Et2O 2. 80 o Me3Si SiMe3, HMPA C, 24 h 75%; (E/Z) 2:1 Allylsilanes from Allyl Alcoholates; General Procedure: [135] An Et 2O soln of the allyl alcohol (e.g., 66 or 67) (1.0 equiv) was treated with MeLi (1.5 equiv) at 08C, followed byMe 3SiSiMe 3 (1.5 equiv) and HMPA (Et 2O/HMPA 1:4). After Et 2O was boiled off under N 2, the mixture was heated at 808C for 24 h. Aqueous workup followed bydistillation provided the desired allylsilane (e.g., 11). 4.4.40.19 Method 19: From Allyl Esters via Allylpalladium(0) Complexes Palladium-catalyzed silylation of allylic esters constitutes a useful protocol for the synthesis of allylsilanes. Two general procedures have been reported; in one, use is made of disilanes to introduce the organosilicon moiety, while in the other, trialkylhalosilanes are used in the presence of samarium(II) iodide and hexamethylphosphoric triamide. With geranyl acetates or neryl acetates, the latter procedure gives terminally substituted allylsilanes with complete control of regio- and stereoselectivity; this is not so in the procedure in which disilanes are used. 4.4.40.19.1 Variation 1: Using Disilanes FOR PERSONAL USE ONLY 4.4.40 Allylsilanes 859 Allylsilanes can be obtained by treatment of allyl trifluoroacetates with organodisilanes in the presence of a catalytic quantity of bis(dibenzylideneacetone)palladium(0) at room temperature. For example, allylsilane 68 is available in excellent yield from the corresponding trifluoroacetate (Scheme 32). [136] Similarly, terminal allylsilane 46 is available from either internal (69) or terminal (70) allylic trifluoroacetates. However, geranyl trifluoroacetate gives terminal allylsilanes with loss of alkene geometry. [136] Scheme 32 By Coupling via ç 3 -Allylpalladium(0) Complexes [136] 11 SiMe 3 1. Me3Si SiMe3 2. Pd(dba)2, THF, rt Ph OCOCF3 94% Ph SiMe3 68 (E/Z) 99:1 Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG for references see p 920
Page 1 and 2: 4.4.40 Product Subclass 40: Allylsi
Page 3 and 4: matching of both partners is approp
Page 5 and 6: pressure. Flash chromatography(sili
Page 7 and 8: Scheme 11 From Allylic Halides by E
Page 9 and 10: similar protocol starting with but-
Page 11 and 12: + PhMe2Si MgCl Cl Br (R,S)-PPFA = +
Page 13 and 14: Scheme 18 Allylsilanes from Vinyl T
Page 15 and 16: Trimethyl(non-2-enyl)silane (44); T
Page 17 and 18: complex which reacts with the carbo
Page 19 and 20: (2-Cyclohexylidenepropyl)trimethyls
Page 21: (2 ” 10 3 kPa)±depressurization
Page 25 and 26: mended for the synthesis of Z-allyl
Page 27 and 28: Allylsilanes 80; General Procedure:
Page 29 and 30: Scheme 39 Allylsilanes from Allyl C
Page 31 and 32: Scheme 42 2-Substituted Allylsilane
Page 33 and 34: FOR PERSONAL USE ONLY 4.4.40 Allyls
Page 35 and 36: Conversion of â-Hydroxy Acids 99 i
Page 37 and 38: Scheme 48 Allylsilanes by Carbocupr
Page 39 and 40: 119. [183,185] The trick for succes
Page 41 and 42: the mixture was washed with sat. aq
Page 43 and 44: (+)-(3R,4E)-N,N-Dimethyl-3-(trimeth
Page 45 and 46: Scheme 57 From Alkenyl Fischer Carb
Page 47 and 48: 4.4.40.37 Method 37: From Allyl Sul
Page 49 and 50: Allyltris(trimethylsilyl)silane (15
Page 51 and 52: the Z-isomer; very little, if any,
Page 53 and 54: Pd2(dba)3 CHCl3 (cat.) (R)-MOP-phen
Page 55 and 56: Scheme 70 An Alk-2-enylsilane by Ca
Page 57 and 58: (E)-Trimethyl[3-(4-tolyl)allyl]sila
Page 59 and 60: FOR PERSONAL USE ONLY 4.4.40 Allyls
Page 61 and 62: Scheme 77 2-Substituted Allylsilane
Page 63 and 64: stream of argon, which was passed t
Page 65 and 66: Z-Vinylsilanes carrying a (tributyl
Page 67 and 68: 1-tert-Butyl-1-vinylcyclohexane (21
Page 69 and 70: 4.4.40.59 Method 59: Allylation of
Page 71 and 72: (5SR,6SR,9RS,10RS)-6,9-Divinyltetra
Page 73 and 74:
Scheme 97 Synthesis of Homoallylic
Page 75 and 76:
Scheme 102 Synthesis of Enantiomeri
Page 77 and 78:
Scheme 106 Diastereoselective Synth
Page 79 and 80:
stirred for 18 h at ±78 8C, and 5
Page 81 and 82:
shaken with some solid K 2CO 3 and
Page 83 and 84:
FOR PERSONAL USE ONLY 4.4.40 Allyls
Page 85 and 86:
FOR PERSONAL USE ONLY References 92
Page 87 and 88:
Page 89 and 90:
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Allylsilanes

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