Salicylic acid, silylation

Reimer-Tiemann reaction, 6 236 of salicylic acid, 22 5 Reinforced composites flax fiber in, 22 594 silylating agents and, 22 701-703 Reinforced plastics, 26 750-751 asbestos applications, 3 311 Reinforced polyester composites, 20 114 Reinforced reaction injection molding (RRIM), 25 456 Reinforcement... 

Carreira and co-workers reported novel Ti(lV) complexes 69 derived from Ti(0 Pr)4, tridentate ligands 67, and salicylic acids such as 68. The complexes serve as competent catalysts for the addition of the methyl acetate-derived silyl ketene acetal to a large range of aldehydes (Eqs. 8B2.16 and 8B2.17) [22]. The salient features of this system include the wide range of functionalized aliphatic and aromatic aldehydes that may be used the ability to carry out the reaction with 0.2-5 mol % catalyst-loading and experimental ease with which the process is executed (Table 8B2.8). Thus the reaction can be carried out at -10 to 0°C, in a variety of solvents, without recourse to slow addition of reagents. The adducts from the catalytic reaction were isolated with excellent enantiopurities up to 99% ee. The original catalyst-preparation... 

Carreira et al. used a chiral BlNOL-derived Schiff base-titanium complex as the catalyst for the aldol reactions of acetate-derived ketene silyl acetals (Scheme 8C.29) [64a]. The catalyst was prepared in toluene in the presence of salicylic acid, which was reported to be crucial to attain a high enantioselectivity. A similar Schiff base-titanium complex is also applicable to the carbonyl-ene type reaction with 2-methoxypropene [64b], Although the reaction, when con-... 

Laik Ali [167] applied BSTFA and MSTFA to the silylation of trace amounts of salicylic acid in acetylsalicylic acid. A 0.5—1-ml volume of the reagent and 50—100 mg of acetylsalicylic acid were heated at 70—80°C in a closed vessel for 30—60 min. As the TMS derivative of acetylsalicylic acid decomposes, an exact evaluation of the analysis is difficult and therefore the author recommended stable methyl derivatives prepared by reaction with methyl iodide and potassium carbonate. 

Saccharin, 363 Salicylic acid, 430 Sandmeyer reaction, 416 Saturated compounds, 50 Saytzeff, 91, 130 Schiff base, 411 Schmidt rearrangement, 406 Secondary carbon, 54 Semicarbazide, 315 Sigma bond, 15 Sigma complex, 205 Silyl ethers, 286 Singlet carbene, 32 Skraup reaction, 459... 

Physostigmine salicylate in 0.5 % aqueous solution was determined by Teare and Borst by freeze-drying of samples of 0.2 ml, and conversion of the compound into its trimethyl silyl derivative by dissolving the residue in 5 yl of dry pyridine and 10 yl of N,0-bis(trimethyl -silyl)acetamide. The solution was allowed to stand for 1 h before injecting 1.2 yl into the gas chromatograph. A 3.8 % SE-30 on Diatoport S column and a temperature of 145°C was used for the analysis. The physostigmine THS and the salicylic acid TMS derivatives were eluted separately. Routine analysis over several days gave a precision of 11.5 %. 

Wittig olefinations continue to be exploited for the synthesis of heterocyclic species. For example, acylphosphoranes (65), formed as intermediates in the condensation of (trimethylsilyl)methylenetriphenylphosphorane and the silyl esters of 0-acyl(aroyl)salicylic acids, undergo intramolecular Wittig reactions producing substituted chromenones (66) (Scheme 14). " Treatment of diox-olanones (67) with (carbethoxymethylene)triphenylphosphorane produces the corresponding a,p-unsaturated esters (68), which are useful precursors to... 

Alkylsilyl cyanides such as Et2Si(CN)2 can be used to silylate dihydroxy compounds such as salicyl alcohol or salicylic acid to obtain 4//-l,3,2-benzodioxasilins (e.g. E = 0 in Equation (5) <86JOC3545 . They can also be prepared regio- and stereoselectively in intramolecular Diels-Alder reactions of R 2Si(OR )(OR ) species (R = Ph or Bu , R = butadienyl, R = substituted vinyl) <91TL1145>. 

Aminosalicylic acid in assessment of reactive oxygen species formation by in vitro Fenton and ozonation reactions and by in vivo ozone-exposure experiments in rats revealed oxidation products as follows salicylic acid, by deamination 2,3-dihydro-xybenzoic acid and 2,5-dihydroxybenzoic acid, from radical or enzymatic hydroxylation 5-amino-2 - hydroxy-N,W-bis(3 - carboxy- 4- hydroxyphenyl)-1,4-benzoquinonediimine, a condensation product of oxidised 5-aminosalicylic acid and 5-amino-2,3,4,6-tetrahydroxybenzoic acid, attributed to hydroxyl radical attack without deamination, identified by high-pressure liquid chromatography electrochemical detector system analysis and by gas chromatography-mass spectrometry analysis of trimethyl silyl derivatives (Kumarathasan et al. 2001). 

A diaryIprolinol silyl ether induces ee < 99% for aldehyde a-alkylation on 1,4-addition to acridinium salts. Computational chemistry has been used to explain stereoinduction by a family of iodooxazoline catalysts developed for enantioselective a-tosyloxylation of ketones by m-CPBA/TsOH. a-Benzoyloxylation of ketones (cyclohexanones and 1-indanones) by dibenzoyl peroxide occurs enantioselectively in the presence of a mixture of 9-amino-(9-deoxy)epi-dihydroquinidine and salicylic acid. ° The scope and limitations of asymmetric a-oxyacylation of cyclic ketones by chiral Ai-alkyl-O-acyl hydroxylamines have also been reported. ... 

NEt3 or DBU in acetonitrile. Similar condensations of O-silylated y9-dicarbonyl compounds with l,3-bis(trimethylsilyloxy)-l-methoxybutadiene (which is readily obtained by quenching of the anion of methyl 3-trimethylsilyloxybut-2-enoate with Me3SiCl 14, at -78 °C in CH2CI2, in the presence of Lewis acids such as TiCL ) likewise afford O-silylated methyl salicylates in high yields [40a-d]. 

Related isoflavones have been prepared, using SPOS, by Harikrishnan and Showalter. Resin-bound salicyl aldehyde derivatives 336, immobilized via a traceless silyl linker unit, were prepared and treated with a Grignard reagent to introduce the first point of diversity. Subsequent re-oxidation with 2-iodoxybenzoic acid (IBX), and deprotection of the methoxymethyl (MOM) group provided ketone 338. Treatment of ketone 338 with amide acetals promoted an unusual cyclization, which concurrently installed R to give 339. Final traceless cleavage with CsF or TBAF releases isoflavones 340 (Scheme 3.59). 

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