- CONVERSION OF SOME ALKENYLTRIMETHYLSILANES INTO SILYL ENOL ETHERS
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The cycloaddition products (5-trimethylsilylisoxazolines) between alkenyltrimethylsilanes and acetonitrile oxide undergo thermolytic rearrangement-cycloreversion to afford silyl enol ethers of retained stereochemistry vs. the starting alkenylsilanes.
- Cunico, Robert F.
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- Novel synthesis routes for the preparation of low toxic vinyl ester and vinyl carbonate monomers
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UV curing of photopolymerizable monomers, like (meth)acrylates, has been utilized for coatings for more than half a century and more recently in further developed areas such as tissue engineering. However, these monomers have major disadvantages, e.g., high irritancy and cytotoxicity, which leads to limited use in tissue engineering regarding health issues. Vinyl esters (VE) and vinyl carbonates (VC) can compete with (meth)acrylates in terms of material properties and have significantly lower toxicity, but lack in cost efficient synthesis methods. The purpose of this communication is to establish new pathways to overcome this drawback. It was shown that VEs can be synthesized either by vinyloxy trimethylsilane or by acetaldehyde in excellent yields. Moreover, a new method to synthesize vinyl chloroformate as precursor for VCs in lab scale was evolved by a catalyzed reaction of vinyloxy trimethylsilane with a phosgene solution. Finally, the cytotoxicity tests showed auspicious results.
- Hofecker, Andreas,Knaack, Patrick,Liska, Robert,Markovic, Marica,Ovsianikov, Aleksandr,Steinbauer, Patrick
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supporting information
p. 3629 - 3641
(2020/10/02)
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- Efficient room-temperature O-silylation of alcohols using a SBA-15-supported cobalt(II) nanocatalyst
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The O-silylation of OH groups of alcohols and phenols with hexamethyldisilazane (HMDS) was achieved in high-to-excellent yields using catalytic quantities of a SBA-15-supported cobalt(II) nanocatalyst (typically 0.5 mol-%) at room temperature and under solvent-free conditions. Furthermore, the heterogeneous catalyst showed an excellent durability and can be conveniently reused by filtration for at least twelve times without any noticeable loss of activity. Copyright
- Rajabi, Fatemeh,Luque, Rafael,Serrano-Ruiz, Juan Carlos
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p. 1823 - 1828
(2012/10/29)
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- Lewis base catalyzed enantioselective aldol addition of acetaldehyde-derived silyl enol ether to aldehydes
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Chiral phosphoramide catalyzed-enantioselective aldol addition of an acetaldehyde-derived trialkylsilyl enol ether to aromatic aldehydes provides protected aldol products in good yields with good to excellent enantioselectivities. Preliminary studies show that the aldolization intermediate (a chlorohydrin adduct) can be trapped with tert-butyl isocyanide to form an α-hydroxy lactone with good selectivity in a singlepot operation.
- Denmark, Scott E.,Bui, Tommy
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p. 10190 - 10193
(2007/10/03)
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- Synthesis of vinyl carbonates for use in producing vinyl carbamates
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A method for making a vinyl carbonate represented by the formula (I): CH2═CHOC(O)X1R1??(I) wherein X1is oxygen or sulfur and R1is a substituted or an unsubstituted aliphatic alkyl, aryl, aryl alkyl, olefinic, vinyl, or cycloaliphatic group comprises: (a) reacting a compound represented by the formula (II): X2C(O)X1R1??(II) ?wherein X2is a halogen other than fluorine, with a compound represented by the formula (III): M1—F??(III) ?wherein M1is selected from a Group IA metal, in the presence of a first phase transfer catalyst and a first organic solvent, to form a compound represented by the formula (IV): FC(O)X1R1??(IV) and (b) reacting a compound represented by the formula (IV) with a compound represented by the formula (V): CH2═CHOSi(R2)3??(V) ?wherein R2is a substituted or an unsubstituted aliphatic alkyl, aryl, aryl alkyl olefinic, vinyl, or cycloaliphatic group, or any combination thereof, in the presence of a metal salt represented by the formula M2—F wherein M2is a Group IA metal, a second phase transfer catalyst, and a second organic solvent, to form the compound represented by formula (I).
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- Synthesis of vinyl carbonates for use in producing vinyl carbamates
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A method for making a vinyl carbonate represented by the formula (I): CH2═CHOC(O)X1R1??(I) wherein X1is oxygen or sulfur and R1is a substituted or an unsubstituted aliphatic alkyl, aryl, aryl alkyl, olefinic, vinyl, or cycloaliphatic group comprises: (a) reacting a compound represented by the formula (II): X2C(O)X1R1??(II) wherein X2is a halogen other than fluorine, with a compound represented by the formula (III): M1—F??(III) wherein M1is selected from a Group IA metal, in the presence of a first phase transfer catalyst and a first organic solvent, to form a compound represented by the formula (IV): FC(O)X1R1??(IV); ?and (b) reacting a compound represented by the formula (IV) with a compound represented by the formula (V): CH2═CHOSi(R2)3??(V) wherein R2is a substituted or an unsubstituted aliphatic alkyl, aryl, aryl alkyl olefinic, vinyl, or cycloaliphatic group, or any combination thereof, in the presence of a metal salt represented by the formula M2—F wherein M2is a Group IA metal, a second phase transfer catalyst, and a second organic solvent, to form the compound represented by formula (I).
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- Mechanism-based inactivation of α-chymotrypsin
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The peptidyl ester derivatives of 2,2-dichlorocyclopropanol and the amide derivative of 2,2-dichlorocyclopropylamine were prepared as novel mechanism-based inactivators of α-chymotrypsin. The esters inactivated α-chymotrypsin irreversibly but the amide did not show any irreversible inhibitory activity toward α-chymotrypsin.
- Ohba, Tsuyoshi,Tsuchiya, Naoki,Nishimura, Kuniko,Ikeda, Eitatsu,Wakayama, Jun,Takei, Hisashi
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p. 543 - 546
(2007/10/03)
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- A Novel Synthetic Route to 2-Halo-3,4-Dicyanopyridines
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2-Bromo-3,4-dicyanopyridine 2 was obtained in moderate yield by reacting 1,1,2,2-tetracyano-3-trimethylsiloxycyclobutane 1 with phosphorus tribromide.Similarly, reaction of 1 with chlorinating reagents such as thionyl chloride and oxalyl chloride led to the corresponding 2-chloro-3,4-dicyanopyridine 3 in 40 percent yield.A reaction mechanism is suggested.
- Lee, Ju-Yeon,Hall, H. K.
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p. 1653 - 1654
(2007/10/02)
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- THE WITTIG REARRANGEMENT AS A PRACTICAL METHOD FOR ALDEHYDE SYNTHESIS
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If the rearrangement of metalated allyl ethers 2 (or 4) is accomplished in the presence of potassium tert-butoxide, primary alkyl groups preferentially migrate to the unsubstituted allylic terminus (γ-position).Enolates 7 and 1-vinylalcoholates 6 (by alkyl migration to the α-position, adjacent to the oxygen atom) are produced in an approximate ratio of 9 : 1.Because of the endo-configuration of their organometallic precursors, the enolates exclusively emerge in the (Z)-configuration as shown by trapping with chlorotrimethylsilane and isolation of the resulting O-silyl (Z)-enethers.Hydrolysis of the latter affords the corresponding aldehydes with good yields. -The rearrangement is mechanistically still obscure.A concerted process as the main reaction mode is unlikely.The intermediacy of zwitterionic metallomers 18 and solvent caged radical pairs 17 is tentatively suggested.
- Schlosser, Manfred,Strunk, Sven
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p. 2649 - 2664
(2007/10/02)
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- Synthesis of Trimethylsilyloxy and Hydroxy Compounds from Carbanions and Bis(trimethylsilyl)peroxide.
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The reactions of bis(trimethylsilyl)peroxide with alkyl, vinyl, alkynyl, aromatic and heteroaromatic anions are described.Depending on the reaction conditions, the trimethylsilyloxy derivatives can be obtained alone or together with the corresponding trimethylsilyl derivatives, which is sometimes the major product.Enolates, generated using magnesium diisopropylamide give the corresponding hydroxycarbonyl compounds in good yields.An attempt to rationalise the above results is given, emphasising the wide use of bis(trimethylsilyl)peroxide in organic synthesis as an electrophilic hydroxylation reagent.
- Camici, Lucia,Dembech, Pasquale,Ricci, Alfredo,Seconi, Giancarlo,Taddei, Maurizio
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p. 4197 - 4206
(2007/10/02)
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- A NEW PRACTICAL SYNTHESIS OF SILYL ENOL ETHERS. PART.I. FROM SIMPLE ALDEHYDES AND KETONES.
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A new, practical route to enoxysilanes is described from simple enolizable aldehydes or ketones, using the trimethylchlorosilane-sodium iodide-tertiary amine reagent in acetonitrile.From certain aldehydes, an onium intermediate has been isolated.A conformational study of this onium intermediate and a thermal unimolecular syn-elimination process may explain the stereoselectivity of the reaction.Such an interpretation can be extended to all the aldehydes and ketones considered.Steric factors related to the nature both of the cabonyl derivative and of the amine play a capital role for the regio- as well as for the stereo-control of the reaction.
- Cazeau, P.,Duboudin, F.,Moulines, F.,Babot, O.,Dunogues, J.
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p. 2075 - 2088
(2007/10/02)
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- Reversal of electronic Substituent Effects in the Retro-Diels-Alder Reaction. A Charge Neutral Analogue of Oxyanion-Accelerated Cycloreversion
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The retro-Diels-Alder reaction of anthracene cycloadducts is influenced by the dienophile substituents in the following ways: (1) electron-withdrawing groups increase the rate of the reaction; (2) strongly conjugating substituents make the reaction much faster than predicted by classical electron-withdrawing or -donating ability, in the best case by a factor of 3 x 106, and (3) there is no observable steric effect, in contrast to literature statements to the contrary.
- Nanjappan, Palaniappan,Czarnik, Anthony W.
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p. 2851 - 2853
(2007/10/02)
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- Enol Ethers, XVII. Acylation of Trimethylsilyl Enol Ethers with Malonyl Dichloride - Synthesis of 4-Hydroxy-2H-pyran-2-ones
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Trimethylsilyl enol ethers of aldehydes 1, acyclic and cyclic ketones 4 and 10, respectively, are acylated by malonyl dichloride (2) at room temperature or even at -60 deg C.After aqueous workup, the 6-unsubstituted 4-hydroxy-2H-pyran-2-ones 3 are obtained from 1-(trimethylsiloxy)alkenes 1, whereas the 5,6-alkylene-bridged 4-hydroxy-2H-pyran-2-ones 11 are formed from 1-(trimethylsiloxy)cycloalkenes 10.Acylation of 2-(trimethylsiloxy)-1-propene (4a) and 3-(trimethylsiloxy)-2-pentene (4b) results in mixtures of 4-(trimethylsiloxy)-2H-pyran-2-ones 5 (main products) and phloroglucinol tris(trimethylsilyl) ethers (6) (by-products).
- Effenberger, Franz,Ziegler, Thomas,Schoenwaelder, Karl-Heinz,Kesmarszky, Thomas,Bauer, Bernd
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p. 3394 - 3404
(2007/10/02)
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- Alkylation and acylation of the iron carbonyl anion [(CO)4FeSi(CH3)3]-. Evidence for 1,3-silatropic shifts from iron to acyl oxygen
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Anions K+[(CO)4FeSi(CH3)3]- (K+-I) and Na+-1 are treated with CH3OSO2F, CH3OSO2CF3, and CH3CH2OSO2F (2 min, 0°C) and C6H5CH2Br and H2C=CHCH2Br (0.5 h, 25°C). Labile, air-sensitive alkyls cis-(CO)4Fe(R)Si(CH3)3 (2) are subsequently isolated in 34-89% yields. When R = CH3 (2a) or CH2C6H2 (2c), room-temperature reductive elimination of RSi(CH3)3 occurs. Reactions of K+-1 or Na+-1 with acylating agents CH3COBr, CH3CH2COBr, and C6H5CH2COBr give H2C=CHOSi(CH3)3, CH3CH= CHOSi(CH3)3, and C6H5CH=CHOSi(CH3)3, respectively. On the basis of low-temperature NMR and IR monitoring and literature precedent, it is proposed that initial acylation of 1 is followed by a rapid 1,3-silatropic shift to give the observable (silyloxy)carbene complex (CO)4Fe=C(CH2R)OSi(CH3)3, followed by a 1,2-hydride shift to give olefin complex (CO)4Fe(RCH=CHOSi(CH3)3), which in turn dissociates RCH=CHOSi(CH3)3. This interpretation is supported by (1) the independent synthesis and rearrangement of (CO)4Fe=C(CH3)OSi(CH3)3 from Li+(CO)4Fe=C(CH3)O- and (CH3)3SiBr, (2) the synthesis of an isolable carbene complex, (CO)4Fe=C(C(CH3)3)OSi(CH3) 3, from 1 and (CH3)3CCOBr, and (3) the reaction of 2a with PPh3 to give (Ph3P)(CO)3Fe=C(CH3)OSi(CH3) 3.
- Brinkman, Kerry C.,Blakeney, Andrew J.,Krone-Schmidt, Wilfried,Gladysz
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p. 1325 - 1332
(2008/10/08)
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- 1-Hydroxymethyl-1-oxo-prostane-derivatives of the E, A and F-series
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The invention disclosed herein relates to pharmacologically active prostaglandin derivatives of the E, F, or A series having on the terminal methylene carbon of the alpha chain a substituent selected from the group consisting of: STR1 wherein R is an alkyl group and R15 is C1 -C4 alkyl, di-C1 -C4 -alkylamino, C1 -C4 alkoxy, and phenyl or phenyl substituted with one or more substituents from the group consisting of C1 -C4, OR, SR, F, or Cl wherein R is as previously defined.
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- 1-Hydroxymethyl-1-1-oxo prostane derivatives of the E and F series
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The invention disclosed herein relates to pharmacologically active prostaglandin derivatives of the E, F, or A series having on the terminal methylene carbon of the alpha chain a substituent selected from the group consisting of: STR1 wherein R is an alkyl group and R15 is C1 -C4 alkyl, C1 -C4 alkoxy, di-C1 -C4 -alkylamino, and phenyl orphenyl substituted with one or more substituents selected from the group consisting of C1 -C4 alkyl, OR, SR, F, or Cl wherein R is as previously defined.
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- 1-Substituted-1-oxo-prostane-derivatives of the E, A and F series
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The invention disclosed herein relates to pharmacologically active prostaglandin derivatives of the E, F, or A series having on the terminal methylene carbon of the alpha chain, a substituent selected from the group consisting of: STR1 wherein R is C1 to C6 alkyl, and phenyl or phenyl substituted with one or more substituents selected from the group consisting of C1 -C4 alkyl, OR16, SR16, F, or Cl, and R16 is C1 to C6 alkyl.
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- Chemistry of enol ethers. LI. Reaction of vinyl silyl ethers with orthoformic esters
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The silyl ethers of enolic forms of ketones react with orthoformates in the presence of zinc chloride at catalyst to form β-ketoacetals.The analogous reaction with the silyl ethers of enolic forms of aldehydes leads to the formation of the tetraacetals of 1,3-dialdehydes.
- Makin, S. M.,Kruglikova, R. I.,Popova, T. P.,Tagirov, T. K.
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p. 630 - 634
(2007/10/02)
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- SUR L'OBTENTION HAUTEMENT REGIO- ET STEREOSELECTIVED'ENOXYSILANES PAR ACTION DU BIS(TRIMETHYLSILYL)ACETAMIDE EN MILIEU HMPT SUR LESS DERIVES CARBONYLES ENOLISABLES
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The authors describe a new and general method for the preparation of enoxysilanes by silylation of enolizable aldehydes and ketones by use of bis(trimethylsilyl)acetamide in HMPT, in the presence of very small quantities of sodium metal(or another basic a
- Dedier, James,Gerval, Pierre,Frainnet, Emile
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p. 183 - 198
(2007/10/02)
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- 1-Hydroxymethyl-1-oxo-prostane derivatives of the E2 series
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Derivatives, analogs, and congeners of prostane having a 1-(hydroxymethyl)-1-oxo-prostane structure in the E2 series.
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