- Kinetics and mechanism of organocatalytic aza-Michael additions: Direct observation of enamine intermediates
-
The imidazoles 1a-g add to the CC-double bond of the iminium ion 2 with rate constants as predicted by the equation log k = sN(N + E). Unfavourable proton shifts from the imidazolium unit to the enamine fragment in the adduct 3 account for the failure of imidazoles to take part in iminium-activated aza-Michael additions to enals.
- Lakhdar, Sami,Baidya, Mahiuddin,Mayr, Herbert
-
-
Read Online
- Synthesis and structure of silyl-substituted imidazol-2-ylidenes and their precursors
-
Previously unknown heterocyclic carbenes and their precursors containing a silicon atom in the side chain were prepared. Their structures were studied by multinuclear 1H, 13C, 15N, and 29Si NMR spectroscopy.
- Komarova,Larina,Abramova,Dolgushin
-
-
Read Online
- Preparation method of meropenem key intermediate N-trimethylsilylimidazole
-
The invention provides a preparation method of N-trimethylsilylimidazole. The method comprises the following steps of: 1) under the protection of inert gas, heating imidazole and hexamethyldisilazaneto T1, and carrying out reaction for 1-4h; 2) at the end
- -
-
Paragraph 0048-0065
(2020/10/20)
-
- Chitosan–silica sulfate nanohybrid: a highly efficient and green heterogeneous nanocatalyst for the regioselective synthesis of N-alkyl purine, pyrimidine and related N-heterocycles via presilylated method
-
Abstract: The presilylation of purine and pyrimidine nucleobases as well as other related N-heterocycles with HMDS utilizing chitosan–silica sulfate nanohybrid (CSSNH) is described. CSSNH is proved to be a useful, highly efficient and eco-friendly heterogeneous nanohybrid catalyst for silylation of nucleobases. The presilylated nucleobases then underwent the reaction with different sources of carbon electrophiles to afford the desired N-alkyl-substituted derivatives in good-to-excellent yields. CSSNH exhibits several advantageous involving ease of handling and preparation, low cost, reusability and environmental benignity. These unique properties render the CSSNH to be an ideal candidate for use in green industrial processes. Graphic abstract: [Figure not available: see fulltext.].
- Behrouz, Somayeh,Soltani Rad, Mohammad Navid,Piltan, Mohammad Amin
-
p. 113 - 124
(2019/07/30)
-
- Preparation method of carbonyl diimidazole
-
The invention discloses a preparation method of carbonyl diimidazole in the technical field of carbonyl diimidazole synthesis. The preparation method comprises the steps of taking imidazole and hexamethyl disilazane as starting materials, obtaining N-trimethylsilyl imidazole through condensation, absorbing a single byproduct, namely ammonia through a sodium hydroxide solution, allowing N-trimethylsilyl imidazole to react with triphosgene to prepare carbonyl diimidazole, and filtering the principal product, namely carbonyl diimidazole, from liquid trimethylchlorosilane for vacuum drying. A removal step is simpler; the byproduct is gaseous and does not influence purity of the product, namely N-trimethylsilyl imidazole; a reactor with higher purity is provided for a subsequent reaction; in areaction process of N-trimethylsilyl imidazole and triphosgene, no catalyst is required to be added; the method is simple to operate; a byproduct of the reaction of N-trimethylsilyl imidazole and triphosgene is liquid trimethylchlorosilane; and carbonyl diimidazole prepared by the method is higher in purity and good in quality.
- -
-
Paragraph 0015; 0016; 0019; 0020; 0023; 0024; 0027; 0028
(2019/02/03)
-
- Desulfurization of hydrocarbons by ionic liquids and preparation of ionic liquids
-
The present invention relates to an improved desulfurization process using an ionic liquid compound of general formula C+A?, where C+ represents an organic cation such as alkyl-pyridinium, di-alkyl imidazolium and tri-alkyl imidazolium; and A? is an anion of halides of iron (III), such as, for example, FeCl4?. The desulfurization process is also improved when producing the ionic liquid compound by heating the reactants using microwave energy. The ionic liquids can be used to desulfurize hydrocarbon mixtures by a liquid-liquid extraction.
- -
-
Page/Page column
(2014/09/16)
-
- Unusual course of diazolees silylation and N-siloxycarbonylation
-
The N-siloxycarbonylation and transamination reactions were studied by an example of diazoles. We found that because of insufficient nucleophilicity of the nitrogen atoms in the first case only the sililylation process occurs, in the second case the low-boiling amine is replaced by the higher boiling one and the process is completed by the formation of O-silyluretans. Pleiades Publishing, Ltd., 2011.
- Kirilin,Belova,Pletneva,Panfilova,Storozhenko,Sheludyakov
-
experimental part
p. 1493 - 1495
(2011/10/18)
-
- MACROCYCLIC ANTAGONISTS OF THE MOTILIN RECEPTOR FOR TREATMENT OF GASTROINTESTINAL DYSMOTILITY DISORDERS
-
The present invention provides conformationally-defined macrocyclic compounds that bind to and/or are functional modulators of the motilin receptor including subtypes, isoforms and/or variants thereof. These macrocyclic compounds, at a minimum, possess adequate pharmacological properties to be useful as therapeutics for a range of disease indications. In particular, these compounds are useful for treatment and prevention of disorders characterized by hypermotilinemia and/or gastrointestinal hypermotility, including, but not limited to, diarrhea, cancer treatment-related diarrhea, cancer-induced diarrhea, chemotherapy-induced diarrhea, radiation enteritis, radiation-induced diarrhea, stress-induced diarrhea, chronic diarrhea, AIDS-related diarrhea, C. difficile associated diarrhea, traveller's diarrhea, diarrhea induced by graph versus host disease, other types of diarrhea, dyspepsia, irritable bowel syndrome, chemotherapy-induced nausea and vomiting (emesis) and post-operative nausea and vomiting and functional gastrointestinal disorders. In addition, the compounds possess utility for the treatment of diseases and disorders characterized by poor stomach or intestinal absorption, such as short bowel syndrome, celiac disease and cachexia. The compounds also have use for the treatment of inflammatory diseases and disorders of the gastrointestinal tract, such as inflammatory bowel disease, ulcerative colitis, Crohn's disease and pancreatitis. Accordingly, methods of treating such disorders and pharmaceutical compositions including compounds of the present invention are also provided.
- -
-
Page/Page column 37
(2010/04/30)
-
- Silica sulfuric acid (SSA) as a highly efficient heterogeneous catalyst for persilylation of purine and pyrimidine nucleobases and other N-heterocycles using HMDS
-
Purine and pyrimidine nucleobases and other N-heterocycles have been silylated with HMDS in excellent yields in the presence of a catalytic amount of silica sulfuric acid (SSA) as a heterogeneous catalyst. SSA utilizes a shorter reaction time and higher yields of silylated nucleobases. SSA is reusable for several times without a decrease in reactivity or yield of silylated adducts. Copyright
- Rad, Mohammad Navid Soltani,Khalafi-Nezhad, Ali,Divar, Masoumeh,Behrouz, Somayeh
-
experimental part
p. 1943 - 1954
(2010/11/16)
-
- Iodine-promoted silylation of alcohols with silyl chlorides. Synthetic and mechanistic studies
-
An efficient silylating system for 1°, 2°, and 3° alcohols, consisting of a silyl chloride/N-methylimidazole/iodine, was developed. Synthetic and mechanistic aspects of this new reagent system, and particularly the role of iodine were investigated in detail using 1H NMR spectroscopy.
- Bartoszewicz, Agnieszka,Kalek, Marcin,Stawinski, Jacek
-
p. 8843 - 8850
(2008/12/21)
-
- Regio- and stereoselective glycosylation: Synthesis of 5-haloimidazole α-ribonucleosides
-
We describe the synthesis of novel 5-haloimidazole ribonucleosides as precursors of modified cobalamins. A regio- and stereoselective glycosylation of protected ribose with silylated 4(5)-haloimidazoles produces 5-haloimidazole ribonucleosides predominant
- Chandra, Tilak,Zou, Xiang,Valente, Edward J.,Brown, Kenneth L.
-
p. 5000 - 5003
(2007/10/03)
-
- Semi-continuous process for preparing bis-silyl carboxamides
-
For preparing bis-silyl carboxamides in a semi-continuous, reacting an amide or the N-trimethylsilyl derivative thereof with a silylating agent and, at the same time, extracting the bis-silyl carboxamide formed by distillation under reduced pressure.
- -
-
-
- Semi-continuous process for preparing bis-silyl carboxamides
-
For preparing bis-silyl carboxamides in a semi-continuous, reacting an amide or the N-trimethylsilyl derivative thereof with a silylating agent and, at the same time, extracting the bis-silyl carboxamide formed by distillation under reduced pressure.
- -
-
-
- Method for producing 1-(trisubstituted silyl)azoles
-
1-Unsubstituted 1H-azole compound, halo trisubstituted silane, and primary amine are reacted to form 1-(trisubstituted silyl)-1H-azole compound which principally accumulates in a liquid phase and hydrohalide salt of the primary amine which principally accumulates in at least one phase different from the liquid phase. In the preferred embodiment, the 1-(trisubstituted silyl)-1H-azole compound so produced is further reacted to produce one or more products and to regenerate the halo trisubstituted silane which is recycled to the earlier reaction.
- -
-
-
- Alkylation, Acylation and Silylation of Azoles
-
Performing alkylation, acylation and silylation reactions in separate deprotonation and nucleophilic displacement steps allows for better control of reaction conditions and facilitates problem handling in these processes.In the alkylation of azoles the alkylating agents and solvents possess individual reaction capabilities which seem to be approximately additive.Monoalkylation occurs if the sum of the normalized reaction potentials is equal or larger than the pKa value of the azole.Dialkylation is avoided by keeping the sum of the normalized reaction potentials below the pKa value of the alkylazole.The applicability of these principles is demonstrated by the development of effective procedures for the methylation, benzylation, acetylation, methoxycarbonylation and trimethylsilylation of azoles.
- Begtrup, Mikael,Larsen, Peter
-
p. 1050 - 1057
(2007/10/02)
-
- Preparation of Trimethylsilyl Ethers of 3-Azetidinols . Scope and Limitations
-
Preparation of the trimethylsilyl ethers of 1-alkyl-3-azetidinols from-non-hindered primary amines and epichlorhydrin by conversion of the intermediate 1-(alkylamino)-3-chloro-2-propanols to their trimethylsilylethers by either N-(trimethylsilyl)acetamide or by 1-(trimethylsilyl)imidazole followed by ring closure in acetonitrile is described.This sequence of reactions fails for aromatic amines, but appears to be general for all primary aliphatic amines, although the condensation of hindered amines with epichlorhydrin occurs slowly.Several novel azetidinols, in which the N-alkyl substituent insefl contains a second heterocyclic system, are reported.In addition, the pKA's of several m- and p-substituted 1-benzylazetidinols correlates well with the Hammett equation.
- Higgins, Robert H.,Watson, Monique R.,Faircloth, William J.,Eaton, Quentin L.,Jenkins, Harvey
-
p. 383 - 387
(2007/10/02)
-
- NOVEL TRICHLOROACETYL BASED SILYLATIONS: SIMPLE METHODS FOR t-BUTYLDIMETHYLSILYLATIONS AND FOR THE PROTECTION OF AMINO GROUPS.
-
A new reagent for t-butyldimethylsilylation has been developed and the known trimethylsilyl trichloroacetate (1) has been shown to be of use for N-silylating amines.
- Galan, Adam A.,Lee, Thomas V.,Chapleo, Christopher B.
-
p. 4995 - 4998
(2007/10/02)
-
- Bis-trimethylsilyl cefamandole and process therefor
-
Bis-trimethylsilyl cefamandole is useful for regenerating cefamandole of excellent purity.
- -
-
-