Derivative of trimethylsilyl

A much more general method for acyl silane synthesis involving silyl diazo intermediates is illustrated in Scheme 1688. The lithiated derivative of trimethylsilyl diazomethane reacts smoothly with alkyl halides in THF solution to give a-trimethylsilyl diazoalkanes in good yields. Oxidative cleavage of the diazo moiety is effected using 3-chloroperbenzoic acid in benzene solution, to give access to a wide variety of acyl silanes in yields of up to 71%. A phosphate buffer (pH 7.6) is used to prevent side reactions. Aromatic acyl silanes clearly cannot be prepared by this chemistry since an aromatic nucleophilic substitution reaction would be required. 

The tricyclic /3-aminocyclohexenone 234 was obtained via intramolecular photoarylation of the bromo arene derivative 233 (Scheme 40). Enamide 234 was treated with sodium hydride, followed by the mesylate derivative of [(trimethylsilyl)methyl]allyl alcohol, to give the allylated compound 235, which was converted to two allyliminium salts 236 and 237. However, attempts to photocyclize these compounds to tetracyclic derivatives were not successful, in contrast to the results of the earlier studies (Scheme 35) in which the spirocyclic system was easily generated in intermediates not rigidly tethered to the aromatic ring. 

Derivative of Trimethylsilyl tri-0- trimethylsilyl)pyranoside Methyl tri-0- trimethylsilyl)pyranoside ... 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

Etherification. The reaction of alkyl haUdes with sugar polyols in the presence of aqueous alkaline reagents generally results in partial etherification. Thus, a tetraaHyl ether is formed on reaction of D-mannitol with aHyl bromide in the presence of 20% sodium hydroxide at 75°C (124). Treatment of this partial ether with metallic sodium to form an alcoholate, followed by reaction with additional aHyl bromide, leads to hexaaHyl D-mannitol (125). Complete methylation of D-mannitol occurs, however, by the action of dimethyl sulfate and sodium hydroxide (126). A mixture of tetra- and pentabutyloxymethyl ethers of D-mannitol results from the action of butyl chloromethyl ether (127). Completely substituted trimethylsilyl derivatives of polyols, distillable in vacuo, are prepared by interaction with trim ethyl chi oro s il an e in the presence of pyridine (128). Hexavinylmannitol is obtained from D-mannitol and acetylene at 25.31 MPa (250 atm) and 160°C (129). 

Gas Chromatography Analysis. From a sensitivity standpoint, a comparable technique is a gas chromatographic (gc) technique using flame ioni2ation detection. This method has been used to quantify the trimethylsilyl ester derivative of biotin in agricultural premixes and pharmaceutical injectable preparations at detection limits of approximately 0.3 pg (94,95). 

In the case of indazoles the reaction of indazole, 5-nitroindazole or 6-nitroindazole with glycosyl halides and mercury(n) cyanide gives exclusively 2-glycosylindazoles (670), (673) and (675) (7QJHC1435). Similarly, the reaction of 1-trimethylsilyl derivatives of indazole, 3-cyanoindazole, 4-nitroindazole, 5-nitroindazole and 6-nitroindazole with 2,3,5-tri-O-acetyl-D-ribofuranosyl bromide gives only, or preferentially, the 2-ribofuranosyl derivatives (670)-(674) 7QJHC117, 70JHC1329). 

Me3SiNHS020SiMe3, CH2CI2, 30°, 0.5 h, 92-98% yield. Higher yields of trimethylsilyl derivatives are realized by reaction of aliphatic, aromatic, and carboxylic hydroxyl groups with A, <9-bis(trimethylsilyl)sulfamate than by reaction with N,<9-bis(trimethylsilyl)acetamide. ... 

Compound 40 has not yet been synthesized. However, there is a large body of synthetic data for nucleophilic substitution reactions with derivatives of 41 [synthesized from aliphatic and aromatic aldehydes, pyridine, and trimethylsilyl triflate (92S577)]. All of these experimental results reveal that the exclusive preference of pathway b is the most important feature of 41 (and also presumably of 40). 

The desilylacetylated qrcloadducts, produced from the reactions of trimethylsilyl-diazomethane with 3-crotonoyl-2-oxazolidinone or 3-crotonoyl-4,4-dimethyl-2-oxa-zolidinone, were transformed to methyl traws-l-acetyl-4-methyl-l-pyrazoline-5-car-boxylate through the reactions with dimethoxymagnesium at -20 °C. When the optical rotations and chiral HPLC data were compared between these two esters, it was found that these two products had opposite absolute stereochemistry (Scheme 7.39). The absolute configuration was identified on the basis of the X-ray-determined structure of the major diastereomer of cycloadduct derived from the reaction of trimethylsilyldiazomethane to (S)-3-crotonoyl-4-methyl-2-oxazolidi-none. 

With the use of trimethylsilyl-substituted starting materials after Denmark et al., the disadvantageous formation of a mixture of isomers can be avoided. The vinyl silane derivatives react by loss of the TMS group in the last step ... 

Interestingly, the diastereofacial selectivity can be reversed in the Strecker reaction of aldimines derived from galactosylamine 1 by simply changing the solvent. When the reaction of trimethylsilyl cyanide with the Schiff bases 2 catalyzed by zinc chloride, is carried out in chloroform instead of 2-propanol, there is a preferred formation of the (.S)-amino nitrile diastereomers63. 

The diastereoselectivity of the zinc iodide catalyzed reaction of the azetidinone I with the trimethylsilyl enolate derivatives of the chiral 3-(l-oxopropyI)oxazolidinones 6 was considerably lower (about 60 40), although independent generation of the zinc enolate, via exchange of the lithium enolate with zinc bromide, afforded the /9-Iactam carboximide derivatives in a ratio (RIS) 80 20177. 

Hydrochloric acid in anhydrous methanol (1 4 volume ratio) has been used to desilylate the trimethylsilyl derivatives of ferrocene, ruthenocene, and os-mocene, the rate coefficients (lO5 ) being ferrocene (5.60, 4.08), ruthenocene (261, 182), and osmocene (104, 80.2) for 0.596 M and 0.477 M hydrochloric acid, respectively, (temperature not quoted)690. 

Potassium or lithium derivatives of ethyl acetate, dimethyl acetamide, acetonitrile, acetophenone, pinacolone and (trimethylsilyl)acetylene are known to undergo conjugate addition to 3-(t-butyldimethylsiloxy)-1 -cyclohexenyl t-butyl sulfone 328. The resulting a-sulfonyl carbanions 329 can be trapped stereospecifically by electrophiles such as water and methyl iodide417. When the nucleophile was an sp3-hybridized primary anion (Nu = CH2Y), the resulting product was mainly 330, while in the reaction with (trimethylsilyl)acetylide anion the main product was 331. 

Structural Identification of Isomeric O-Trimethylsilyl Derivatives of Some Hexuronic Acids, J. F. Kennedy, S. M. Robertson, and M. Stacey, Carbohydr. Res., 57 (1977) 205-214. 

Alkali metal derivatives of 2-(trimethylsilyl)aminopyridines can be further derivatized by insertion of 1,3-dicyclohexylcarbodiimide. Functionalized guani-dinates are formed in this reaction via a 1,3-silyl shift. Scheme 170 illustrates the reaction sequence as well as the preparation of an aluminum complex of the modified ligand, which exhibits pseudo jS-diketiminate binding of the metal center, thus exemplifying the coordinative versatility of this new multi-N-donor system. ... 

Other thietane derivatives have been obtained by isomerization of nitrogen-containing heterocycles. The reaction of an acyl isothiocyanate (RCONCS) with diphenyldiazomethane gave 20 and this isomerized in solution to the tetraphenyl-3-thietanone 21 <96BSB253>. Additionally, the isoxazolidine 22 was converted into 23 by the action of trimethylsilyl iodide and zinc iodide <96H1211>. 

The cyclisation of naphthyl propargyl ethers occurs efficiently under microwave irradiation leading to naphthopyrans, but naphthofurans are formed in the presence of base <96JCR(S)338>. The thermal rearrangement of naphthyl 3-trimethylsilylprop-2-ynyl ethers yields the 4-trimethylsilyl derivatives of naphthopyrans <96H(43)751>. 

With the successful chemistry of the cymantrenes and the (cyclobuta-diene)tricarbonyl iron, the quest for tetraethynylated cyclobutadienes based on CpCo-stabilized complexes arose. Why would they be interesting Whereas all derivatives of 63 and 68 exhibit reasonable stability when their alkynyl substituents are protected by either an alkyl or a trimethylsilyl group, the desilylated parents are isolated only with difficulty and are much more sensitive. 

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