Efficient Synthesis of Salicylates by Catalytic [3 + 3] Cyclizations of 1,3-Bis(silyl enol ethers) with 1,1,3,3-Tetramethoxypropane (original) (raw)
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Convenient Synthesis of N-Trimethylsilylaminotitanium Trichlorides
Zeitschrift für anorganische und allgemeine Chemie, 1998
Bis(N-trimethylsilylamino)plumbylenes 1 {[Me 3 Si(R)N] 2 Pb with R = t Bu (a), Me 3 Si (b), 9-(9-borabicyclo[3.3.1]nonyl) (c)} react smoothly with an excess of TiCl 4 to give PbCl 2 and N-trimethylsilylaminotitanium trichlorides 3 a±c. In contrast, the analoguous reaction of the corresponding stannylenes 2 a±c leads to mixtures containing unidentified Ti III compounds, the amides 3 a or 3 b, bis[bis(trimethylsilyl)amino]titanium dichloride 4 b and bis(amino)tin dichlorides 5 a±c. The crystal structure of 3 a was determined by X-ray structural analysis. Compound 3 a is a dimer in the solid state with distorted trigonal pyramidal surroundings of the titanium atoms. Each titanium atom bears two l 2 -Cl ligands which are in axial (d Ti±Cl = 250.7(1) pm) and equatorial positions (d Ti±Cl = 247.0(1) pm) and two terminal chloro ligands, one in axial (d Ti±Cl = 228.0(1) pm) and one in equatorial position (d Ti±Cl = 221.1(1) pm). The equatorial Ti±N bonds are short (183.8(2) pm).
Organic Letters, 2010
B(C 6 F 5 ) 3 promotes regio-and stereoselective cyclizations of unsaturated alkoxysilanes to generate oxasilinanes and oxasilepanes. The same products are available directly from alkenols via tandem silylation and hydrosilylation. Intramolecular hydrosilylation of alkenes is an important transformation in organic synthesis.1 Initially investigated for unsaturated silanes,2 the methodology is now often applied to unsaturated alkoxy-and aminosilanes,3 where stereospecific oxidative cleavage of the newly formed C-Si bond enables stereodefined synthesis of diols and aminoalcohols. 4 , 5 The majority of examples involve metal-catalyzed 5-endo or 5-exo ring closures, although six-membered cyclizations have been reported.1 , 3 , 6 We now report regio-and stereoselective formation of oxasilinanes and oxasilepanes via formation and cyclization of unsaturated alkoxysilanes in the presence of a nonmetal catalyst.
Acta Crystallographica Section C Crystal Structure Communications, 1999
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RSC Advances, 2012
General information and experimental procedures Solvents were dried by the standard procedures. 1 H and 13 C NMR spectra were determined in CDCl 3 or DMSO-d 6 on a BRUKER Avance (1 H: 400 MHz, 13 C: 100 MHz). IR spectra were obtained on a SHIMADZU FT-IR 8300 spectrophotometer using KBr disc. Mass spectra were obtained on SHIMADZU LCMS 2010 instrument. All the reactions were monitored by thin layer chromatography (TLC) using silica gel 60 F254 plates (Merck). The melting points were determined in open capillary tube on a TEMPO melting point apparatus and are uncorrected. The UV spectra were obtained on SHIMADZU UV-160 A. General procedure Synthesis of O-allylated or prenylated-5-aryldiazenyl salicylaldehydes (3a-d). To a stirred solution of 10 mmol diazenylsalicylaldehyde 2 in 25 ml DMF, in the presence of 15 mmol anhydrous potassium carbonate, was added dropwise a solution of 1.5 mmol of allyl bromide in 5 ml DMF. The resulted mass was then further stirred at room temperature to complete the reaction as monitored by TLC (10-12 h). It was then poured into ice with constant stirring. The solid precipitates were filtered, washed with cold water, and dried at room temperature. The products 3a-b were received quantitatively. Similarly prenyl bromide was used to obtain Oprenylated salicylaldehyde derivatives 3c-d.
Synthesis, 1985
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