Carbon acidity. 77. Ion pair carbon acidities of some silanes in tetrahydrofuran
摘要:
The relative solvent-separated ion pair (SSIP) lithium acidity (PK(Li)/THF) and contact ion pair (CIP) cesium acidity (pK(Cs/THF)) were obtained for 9-fluorenyltrimethylsilane (1) (21.3, 21.6, respectively) and 9-fluorenyl-tert-butyldimethylsilane (2) (20.3, 20.6, respectively) in THF. Values for pK(Cs/THF) were determined at 25-degrees-C for (p-biphenylylmethyl)-tert-butyldimethylsilane (3), 35.4, benzyltrimethylsilane (4), 37.5, alpha,alpha-bis(trimethylsilyl)toluene (5), 34.1, 2-(trimethylsilyl)-1,3-dithiane (6), 33.5, (trimethylsilyl)acetonitrile (7), 28.8, and tris(trimethylsilyl)methane (8), 36.8. Some thermodynamic parameters were determined by measurements at other temperatures, and some ionic acidities (pK(FI)) were determined by conductivity studies. Carbanion stabilization by these silyl substituents varies from about 1 to over 3 pK units in different systems. 9,9-Bis(trimethylsilyl)fluorene (9) was found to undergo silyl transfer on treatment with various carbanions, but this reaction is slower than proton transfer.
Aromatic acylsilanes such as benzoyltrimethylsilane react with ytterbium metal to give symmetrical 1,2-diarylacetylenes in good yields. Aliphatic acylsilanes are reduced with lanthanoid reagents such as Yb metal and SmI2 to afford α-silylalcohols.
The compounds (Me3Si)xCH(3−x)Cl (x = 1–3), (Me3Si)xCH(3−x)Br (x = 1, 3) and Me3SiCMe2Br have been found to react with 90% acetone or 80% ethanol at 70° at rates too small for convenient measurement. Towards aqueous acetone, the compound PhMe(Me3Si)CBr is 110 times less reactive at 50° than PhMe2CBr at 0°. It is concluded that relative to α-Me, α-t-Bu or α-Me3Si groups decrease the ease of formation
The electron-releasing effects of mono-, bis-, and tris-(trimethylsilyl)methyl groups. The importance of hyperconjugation in the electronic effects of α-metalloalkyl groups
作者:A.R. Bassindale、C. Eaborn、D.R.M. Walton、D.J. Young
DOI:10.1016/s0022-328x(00)80087-x
日期:1969.11
release by the (Me3Si)xCH3-x groups, increase in the order x = 0 < 3 < 1 < 2 for both the m- and p-compounds. The 19F chemical shifts in the p-(Me3Si)3CH3-xC6H4F compounds indicate the same order of electron release. This order is not consistent with attribution of effects of the (Me3Si)xCH3-x groups entirely or even primarily to inductive release of electrons by the Me3Si groups, but is consistent with
高氯酸甲醇水溶液对(Me 3 Si)x CH 3- x C 6 H 4 SiMe 3化合物中芳基-Si键的裂解速率,以及因此由(Me 3 Si)x CH 3-释放的电子x个组,对于m-和p-化合物,按x = 0 <3 <1 <2的顺序增加。p-(Me 3 Si)3 CH 3- x C 6 H 4中的19 F化学位移F化合物表示电子释放的顺序相同。这个命令是不与的(ME的效果归因一致3 Si)的X CH 3- X基团完全或甚至主要由ME电子感应释放3 Si基团,但是与从ME电子hyperconjugative释放一致3 Si-C键。
Stereoselective Peterson Olefinations from Bench-Stable Reagents and<i>N</i>-Phenyl Imines
作者:Manas Das、Atul Manvar、Maïwenn Jacolot、Marco Blangetti、Roderick C. Jones、Donal F. O'Shea
DOI:10.1002/chem.201500475
日期:2015.6.8
The synthesis of bench‐stable α,α‐bis(trimethylsilyl)toluenes and tris(trimethylsilyl)methane is described and their use in stereoselective Peterson olefinations has been achieved with a wide substrate scope. Product stereoselectivity was poor with carbonyl electrophiles (E/Z ∼1:1 to 4:1) though this was significantly improved by employing the corresponding substituted N‐benzylideneaniline (up to 99:1)
<i>Z</i>-Stereoselective Aza-Peterson Olefinations with Bis(trimethylsilane) Reagents and Sulfinyl Imines
作者:Manas Das、Donal F. O’Shea
DOI:10.1021/acs.orglett.5b03519
日期:2016.1.15
Highlystereoselective aza-Peterson olefinations from bench-stable α,α-bis(trimethylsilyl)toluene reagents and N-substituted imines have been achieved using TMSO–/Bu4N+ as Lewis base activator in THF. Remarkably, and for the first time, N-t-butanesulfinyl imines were utilized for the synthesis of Z-stilbenes with excellent selectivities, while N-aryl imines generated E-stilbenes under identical reaction