Allylsilanes

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4.4.40.28 Method 28: From Alkynes and á-Silyl Organocopper Reagents Functionalized allylsilanes have been prepared by carbocupration of alkynes with á-silylated organocopper reagents, generated in situ from silylated Grignard reagents such as [(trimethylsilyl)methyl]magnesium chloride or the corresponding organolithium reagents, followed bytrapping of the resultant ã-silylated vinylcopper intermediates with electrophiles. [172±176] Thus, allylsilane 106 [173] can be obtained bythe treatment of ethoxyalkyne 105 with an organocopper reagent (Scheme 47). Similar reactions on allenic sulfones give 2-[(trimethylsilyl)methyl]allylic sulfones. [177] However, in some specific cases, such as á-acetylenic and -allenic oxiranes, á-allenic methanesulfonates, or the disulfonate 107, the carbocupration reaction gives products resulting from double 1,3-substitution (1,3 with respect to each sulfonate group), bynucleophilic attack of the copper atom, followed byreductive elimination; an example of this procedure is the preparation of valuable conjunctive reagent 108, presumablybytwo successive 1,3-substitution reactions. [172] In general, two variations of this carbocupration process have been used, for the one, a stoichiometric amount of copper(I) salt is used, and the other is a catalytic version. Scheme 47 Allylsilanes by Carbocupration of Alkynes [172,173] OEt 1. Me3SiCH2Cu MgClBr 2. NH3 buffer OEt 105 106 MsO OMs 107 FOR PERSONAL USE ONLY 872 Science of Synthesis 4.4 Silicon Compounds SiMe3 Me 3SiCH 2Cu MgClBr LiBr (2 equiv) 4.4.40.28.1 Variation 1: Stoichiometric Carbocupration with a Copper(I) Salt Carbocupration of alk-1-ynes with á-silylated organocopper reagents, prepared in situ from [(trimethylsilyl)methyl]magnesium chloride and an equimolar amount of purified copper(I) salt, gives synthetically useful and thermally stable ã-silylated vinylcopper intermediates; the latter undergo a range of reactions including hydrolysis, iodination, carbonation, oxidative dimerization, alkylation, and so forth, to provide functionalized allylsilanes with retention of geometryof the C=C bond. [172,173,178] This is exemplified bythe preparation of allylsilanes 111 and 112 from alkyne 109 via the ã-silylated vinylcopper species 110 (Scheme 48). [178] Incidentally, allylsilanes derivable from the E-stereoisomer of 110 have been prepared by a similar carbocupration of trimethyl(prop-2-ynyl)silane, [173] as in the related zirconium-promoted carbometalation process. [80] Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG SiMe3 OMs Me 3Si 108 SiMe 3
Scheme 48 Allylsilanes by Carbocupration with a Stoichiometric Amount of a Copper(I) Salt [178] 109 Bu Me3SiCH2Cu MgClBr LiI Et2O Cu Bu 110 SiMe3 NH3 buffer I Bu 111 78% (2-Butylallyl)trimethylsilane (111); Typical Procedure: [173] To an Et 2O (50 mL) suspension of CuBr (2.2 g, 15 mmol) and 1 M LiI in Et 2O (20 mL, 20 mmol) was added 0.9 M Me 3SiCH 2MgCl in Et 2O (17 mL, 15 mmol) at 08C. The mixture first gave a yellow precipitate and then became a homogeneous pale green soln, which was stirred at ±58C for 1 h. After addition of hex-1-yne (109; 1 g, 12.5 mmol), the mixture was allowed to warm to 108C and stirred at this temperature for 18 h. The resulting brown soln was then hydrolyzed with NH 3 buffer soln (100 mL). The mixture was filtered and decanted, and the organic layer was washed with sat. aq NaCl (10 mL) and dried (MgSO 4). The solvent was removed under reduced pressure and the residue was distilled through a 10-cm Vigreux column; yield: 1.66 g (78%); bp 708C/10 Torr. 4.4.40.28.2 Variation 2: Copper-Catalyzed Carbometalation of Alk-2-yn-1-ols Treatment of the magnesium alkoxides of alk-2-yn-1-ols with [(trimethylsilyl)methyl]magnesium chloride in the presence of a catalytic amount of freshly purified copper(I) salt in diethyl ether gives 2-hydroxymethyl-substituted alk-2-enylsilanes, as in, for example, the formation of bifunctional conjunctive reagents 113 (Scheme 49). [173,175,176] Of note is the requirement that chloride should be used as the sole halogen for both the organomagnesium and copper salts for good yields. [176] Scheme 49 Allylsilanes by Copper-Catalyzed Carbometalation of Alk-2-yn-1-ols [175,176] R 1 OH FOR PERSONAL USE ONLY 4.4.40 Allylsilanes 873 1. s-BuMgCl, Et2O, −20 oC, 10 min 2. Me3SiCH2MgCl, 10% CuCl −20 oC to rt, 3 d 3. NH4Cl buffer (pH 9) R 1 I 2 SiMe 3 113 R 1 = Me 64% R 1 = SPh 81% [(Z)-2-(Hydroxymethyl)but-2-enyl]trimethylsilane (113, R 1 = Me): [176] But-2-yn-1-ol (3.5 g, 50 mmol) was added slowly by syringe to 2.0 M s-BuMgCl in Et 2O (25 mL, 50 mmol), diluted in Et 2O (120 mL), at ±208C. After this mixture had stirred for 10 min at ±208C, CuCl (500 mg, 5 mmol) was added all at once, quicklyfollowed bythe addition of 0.71 M Me 3SiCH 2MgCl in Et 2O (70 mL, 50 mmol) bycannula. The mixture was allowed to reach rt, and was stirred at this temperature for 3 d before being poured into a cold (0 8C) pH 9 NH 4Cl buffer soln (450 mL sat. NH 4Cl +50 mL sat. NH 4OH). The aqueous phase was separated and extracted with Et 2O (6 ” 70 mL). The combined organic layers were dried (MgSO 4), filtered, and concentrated in vacuo. The crude oil was purified by Kugelrohr distillation; product 113 was obtained as a clear, colorless oil; yield: 5.03 g (64%); bp 768C/ca. 5 Torr. Sarkar, T. K., SOS, (2002) 4, 837. 2002 Georg Thieme Verlag KG OH Bu 112 SiMe3 SiMe 3 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 and 22: (2 ” 10 3 kPa)±depressurization
Page 23 and 24: Scheme 31 Allylsilanes from Allyl A
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: Conversion of â-Hydroxy Acids 99 i
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 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 85 and 86: FOR PERSONAL USE ONLY References 92
Page 87 and 88:
FOR PERSONAL USE ONLY References 92
Page 89 and 90:
FOR PERSONAL USE ONLY References 92
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