- Stereospecific synthesis of 1,2-difunctionalized buta-1,3-dienes via tandem [3,3]-[3,3] sigmatropic rearrangements
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Thermolysis of bis-thiocarbamates derived from but-3-yne-1,2-diols resulted in the formation of buta-1,3-dienes with carbamoylthio groups in positions 1 and 2 with good to excellent yields. The stereochemistry of the products is controlled by substituents
- Banert, Klaus,Schlott, Jana
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- Complexes PhMgBr·nMgBr2·mNEt3 in the reaction with acetylene
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Kinetics of the reaction of acetylene with two phenylmagnesium bromide reagents of different magnesium bromide content (Br/Mg 1.08 and 1.27) in diethyl ether in the presence of various additions of triethylamine (TEA) were investigated. The reagent of average stoichiometry PhMgBr·2TEA reacts about 20 000 times faster than in the absence of the amine. Elevated content of magnesium bromide in the reagent enhances the accelerating effect of the amine. The complicated relationships obtained enabled us to draw conclusions on the structure and reactivity of the title complexes. At moderate magnesium bromide content species 2PhMgBr·MgBr2 dominate and preferentially complex with TEA giving solvates more reactive than PhMgBr·TEA, whose formation takes place at a higher amine content.
- Paellin, Vello,Tuulmets, Ants
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- Cascade reactions: Sequential homobimetallic catalysis leading to benzofurans and β,γ-unsaturated esters
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The concatenation between a Pd(0)-promoted deallylation catalytic cycle and a Pd(II)-promoted heterocyclization catalytic cycle (an example of what we have named "sequential homobimetallic catalysis") has been shown to occur starting from 1-(2-allyloxyphenyl)-2-yn-1-ols 1 to afford 2-benzofuran-2- ylacetic esters 2 and β,γ-unsaturated esters in high yields under carbonylative conditions. In view of the conceptual as well as the synthetic importance of the process, the mechanistic aspects and the synthetic scope of the reaction have been investigated in detail. All the experimental evidence is in agreement with the sequential homobimetallic mechanism, and the reaction has proven to be of general synthetic applicability.
- Gabriele, Bartolo,Mancuso, Raffaella,Salerno, Giuseppe,Costa, Mirco
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p. 1101 - 1109
(2007/10/03)
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- Use of propargyl glycine amino propargyl diol compounds for inhibiting plasma renin activity
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Compounds characterized generally as propargyl glycine amino propargyl diol derivatives are useful for treatment of a disorder mediated by inhibiting plasma renin activity. Compounds of particular interest are those of Formula I wherein A is selected from
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Page column 14 - 15
(2010/01/30)
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- Mechanism of the reaction of acetylene with Grignard reagents
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Kinetics of the reaction between acetylene and phenylmagnesium bromide were investigated in diethyl ether in the presence of small additions of triethylamine and without a catalyst. The mechanistic scheme suggested by Grignard et al. was supplemented with the reaction of bromomagnesiumacetylene with the Grignard reagent. The rate constants for individual reactions were determined. Triethylamine catalyzes the reactions to different extents, the conversions of bromomagnesiumacetylene being the most susceptible to the catalysis. The possible ways of the action of the catalyst were discussed and the importance of nucleophilic assistance was stressed.
- Paellin, Vello,Otsa, Enn,Tuulmets, Ants
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p. 149 - 152
(2007/10/03)
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- Synthesis, structure and properties of 3,9,15-tri- and 3,6,9,12,15,18-hexasubstituted Dodecadehydro[18]annulenes(C18H3R3 and C18R6) with D(6h)-symmetry
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3,9,15-Tris(p-tert-butylphenyl)dodecadehydro[18]annulene (6) and 3,6,9,12,15,18-hexasubstituted dodecadehydro[18]annulenes (7, 8, and 9) have been prepared. These compounds were shown to be heated up to 150°C without decomposition. The molecular structure
- Suzuki, Riho,Tsukuda, Hiroko,Watanabe, Naoto,Kuwatani, Yoshiyuki,Ueda, Ikuo
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p. 2477 - 2496
(2007/10/03)
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- Pyrethroid esters
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A compound in all possible stereoisomeric forms and mixtures thereof of the formula STR1 wherein the substituents are defined as in the specification having pesticidal properties.
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- IMPROVED SYNTHESIS OF TRICYCLO(5.2.1.04,10)DECANE-2,5,8-TRIONE BY A PAUSON-KHAND INTRAMOLECULAR BIS-ANNULATION
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The title compound 1 has been synthesized from diol 3a, either directly or after protection of the two hydroxy groups as benzyl ethers, by an intramolecular Pauson-Khand bis-annulation, followed by catalytic hydrogenation and oxidation in overall yields ranging from 15percent (free diol) to 35percent (dibenzyl ethers).
- Almansa, Carmen,Carceller, Elena,Garcia, M. Lluisa,Torrents, Alba,Serratosa, Felix
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p. 381 - 390
(2007/10/02)
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- Steroidal Silicon Side-Chain Analogues as Potential Antifertility Agents
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A number of silicon-substituted analogues of ethynylestradiol that exhibit modified and enhanced biological activities have been synthesized.Particularly noteworthy are a group of estradiol analogues that exhibit high antifertility potency and markedly reduced estrogenic activity.The best compounds synthesized are 17α-estradiol (5) and 17α-estradiol (33), which show a separation of antifertility from estrogenic activity in the rat.The results of structure-activity studies indicate a good correlation between the observed biological activities and the calculated van der Waals volumes of the three variable silicon substituents.
- Peters, Richard H.,Crowe, David F.,Tanabe, Masato,Avery, Mitchell A.,Chong, Wesley K. M.
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p. 646 - 652
(2007/10/02)
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- Synthesis of 9- and 10-membered rings by the intramolecular Michael addition of malonate on enone and ynone
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The base-catalysed (Cs2CO3 in THF/DMF) intramolecular Michael addition of β-ketoester-ynones 7-10 and -enone 11 is reported.Macrocyclization (Table 1), which produced the corresponding medium rings, was observed in 25-50percent yield.
- Deslongchamps, Pierre,Roy, Bernard L.
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p. 2068 - 2075
(2007/10/02)
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- SYNTHETIC STUDIES IN THE CARDENOLIDE SERIES-II STEREOSPECIFIC INTRODUCTION OF C-17 SIDE CHAIN
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Direct preparation of 14β-hydroxy steroids from 14α-H compounds is described; a 15β-hydroxy-14α-H compound is also obtained.Grignard reagents react with 14β-hydroxy-androstan-17-one in the "normal way", giving a 17β-side chain, but surprisingly organolithium reagents give the unexpected 17α-side chain.
- Beloeil, J. C.,Bertranne, M.,Fetizon, M.
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p. 3937 - 3942
(2007/10/02)
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- The reaction of some propargyl alcohols with benzeneselenenyl chloride
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The reaction of benzeneselenenyl chloride with twenty-two propargyl alcohols in methylene chloride solution is reported.Products of both Markownikoff and anti-Markownikoff regiochemistry are formed in an anti stereospecific manner.The regioselectivity or specificity is found to be very dependent upon the nature of the substituents geminal to the alcoholic moiety.In general the presence of bulky substituents geminal to the alcoholic moiety tend to favour formation of the anti-Markownikoff adduct under conditions of kinetic control.The Markownikoff adducts are found to be favoured thermodynamically.
- Garratt, Dennis G.,Beaulieu, Pierre L.,Morisset, Veronique M.
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p. 927 - 934
(2007/10/02)
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- Novel cyclopentanones
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Novel cyclopentanones of the formula STR1 wherein AlK is alkyl of 1 to 4 carbon atoms, R is selected from the group of hydrogen and α-tetrahydropyranyl and the Ys are hydrogen or together represent a double bond with the proviso that when R is hydrogen, the Ys are hydrogen as well as products of the formula STR2 wherein AlK is alkyl of 1 to 4 carbon atoms and products of the formula STR3 wherein R and AlK have the above definitions which are useful intermediates in the production of prostaglandins.
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- Diacetylenic alcohol corrosion inhibitors
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The corrosion of ferrous metals by corrosive acids at elevated temperatures is inhibited by adding to environments containing the acids an effective amount of a novel α, Ω (hereinafter alpha , omega , respectively) diacetylenic diol (e.g., with two acetylenic functionalities) having the structural formula: STR1 where R is an aliphatic, alicyclic or aromatic residue containing from 1 to about 12 carbon atoms and may include one or more functional groups such as halogen atoms, carbonyl, carboxyl, carbamyl, amino, formyl or nitroso radicals or other functional groups without impaired performance. The diacetylenic diols may be employed in combination with other corrosion inhibitors.
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