3239-33-6Relevant academic research and scientific papers
Palladium-Catalyzed Formal Hydroalkylation of Aryl-Substituted Alkynes with Hydrazones
Yu, Lin,Lv, Leiyang,Qiu, Zihang,Chen, Zhangpei,Tan, Ze,Liang, Yu-Feng,Li, Chao-Jun
, p. 14009 - 14013 (2020/06/10)
We have developed an unprecedented Pd-catalyzed formal hydroalkylation of alkynes with hydrazones, which are generated in situ from naturally abundant aldehydes, as both alkylation reagents and hydrogen donors. The hydroalkylation proceeds with high regio- and stereoselectivity to form (Z)-alkenes, which are more difficult to generate compared to (E)-alkenes. The reaction is compatible with a wide range of functional groups, including hydroxy, ester, ketone, nitrile, boronic ester, amine, and halide groups. Furthermore, late-stage modifications of natural products and pharmaceutical derivatives exemplify its unique chemoselectivity, regioselectivity, and synthetic applicability. Mechanistic studies indicate the possible involvement of Pd-hydride intermediates.
Stereoselective synthesis of trisubstituted alkenes via cobalt-catalyzed double dehydrogenative borylations of 1-alkenes
Wen, Huanan,Zhang, Lei,Zhu, Suzhen,Liu, Guixia,Huang, Zheng
, p. 6419 - 6425 (2017/11/09)
A highly selective cobalt-catalyzed single and double dehydrogenative borylations (DHBs) of terminal alkenes have been developed for the synthesis of trans-monoborylalkenes and diborylalkenes, respectively. While the cobalt-catalyzed double DHBs of aryl 1
Mechanistic switch via subtle ligand modulation: Palladium-catalyzed synthesis of α,β-substituted styrenes via C-H bond functionalization
Flores-Gaspar, Areli,Martin, Ruben
, p. 1223 - 1228 (2011/06/26)
A new catalyst system able to efficiently perform the synthesis of styrenes via C-H bond functionalization and a subtle ligand modification are described. The high level of activity achieved allows for the synthesis of highly functionalized α,β-substituted styrenes, even the elusive E-configured trisubstituted olefins, in a regio- and stereoselective manner. Mechanistic experiments allowed for the identification of the corresponding synthetic intermediates.
A novel and efficient method for the olefination of carbonyl compounds with Grignard reagents in the presence of diethyl phosphite
Wang, Tongqiang,Hu, Yuanyuan,Zhang, Songlin
supporting information; experimental part, p. 2312 - 2315 (2010/07/09)
The widely available carbonyl compounds react with Grignard reagents in the presence of diethyl phosphite to give the corresponding olefins in good to excellent yields: A range of conjugated dienes, terminal olefins, multisubstituted-alkenes and conjugated enynes could be readily obtained by the method in mild conditions.
Novel alkylidenating agents of iron(III) derivatives by base-mediated α,μ-dehydrohalogenation and their chemical trapping by cycloaddition
Eisch, John J.,Sohn, Jane U.,Rabinowitz, Edon J.
experimental part, p. 2971 - 2977 (2010/08/20)
Studies of the reactions between group 4 metal, chlorides (M = Ti, Zr, Hf) and methyllithium at -78 °C in toluene can lead to methylidene-metal complexes, H2C=MCl2, by a sequence of monomethylation, α-carbon lithiation and α,μ-elimination of LiCl. Here study of the preparation of alkylidene derivatives of iron was attempted by the interaction of FeCl3 with n-butyllithium in various ratios at -78 °C. The presence of any resulting butylidene-iron(III) derivative, nPrCH=FeE (E = Cl, nBu), was probed by adding chemical trapping agents, such as diphenylacetylene, benzonitrile, methyl benzoate and benzophenone. In each experiment the hydrolyzed products were consistent with a cycloaddition reaction of nPrCH=FeE with the trapping agent. The products from, di-phenylacetylene and from, benzonitrile with D2O workup are uniquely in accord with such a carbene precursor. A 3:1 ratio of nBuLi/FeCl3 gave the optimal yield of nPrCH=FenBu, ca. 80%, from, the MBu2FeCl precursor. When a 3:1. reaction mixture was simply brought to 25 °C and hydrolyzed, the purple alkylidene-iron complex decomposed completely to iron metal. A study of a 3:1 interaction of PhCH2MgCl and FeCl3 under similar conditions and trapping with diphenylacetylene provided evidence for the formation of PhCH=FeCH2Ph in ca. 40%. These results support; the hope that alkylidene-iron(III) analogs of the Grubbs reagents may be accessible by this process.
Modern Friedel-Crafts chemistry. Part-29. Cyclialkylation of some triphenylated propane, butane and pentane substrates to diphenylated indans under Friedel-Crafts conditions
Khalaf, Ali A.,Awad, Ibrahim M.,El-Emary, Talaat I.,Abd El-Aal, Hassan A. K.
scheme or table, p. 300 - 305 (2009/06/25)
Reactions under Friedel-Crafts cyclialkylation conditions produced : isomeric 1,2-diphenylindans from 1,2,3-triphenyl-(1- or 2-)propanol and 1-chloro-2,3,3-triphenylpropane, trans-2-benzyl-1-phenylindan from 2-benzyl-1,3-diphenyl-2-propanol, isomeric 1-me
Reactions of unsaturated azides, 12[≠] azido-1,2,3-triphenylpropenes of varying stabilities: A corrigendum of structure assignment
Banert, Klaus,Hagedorn, Manfred,Liedtke, Christine,Melzer, Antje,Schoeffler, Claudia
, p. 257 - 267 (2007/10/03)
A reinvestigation of the reaction between 2,3-diphenyl-2-H-azirine (1) and phenyldiazomethane (2) has shown that a literature report has to be corrected since no vinyl azide 4 but rather the allylic compound 3-azido- 1,2,3-triphenyl-1-propene (3) is produced. This stable substance, which can also be prepared by substitution reactions of allylic bromide (E)-10 or from alcohol (E)-11, may be separated into its geometrical isomers (E)-3 and (Z)- 3, although these equilibrate through rapid [3,3] sigmatropic migration of the azido group. Attempts to synthesize 4 by dehydration of azido alcohols 7 using methanesulfonyl chloride and sulfur dioxide or by elimination of hydrogen chloride from azides 15 led only to 3 and 2-benzyl-2,3-diphenyl-2H- azirine (14). This heterocycle, which can also be prepared by Neber rearrangement, has been found to be the thermal and photochemical decomposition product of the unstable vinyl azides 4. However, dehydrations of 7 using thionyl chloride at low temperature have led to the first isolation of 1-azido-1,2,3-triphenyl-1-propenes (4). Starting with 3 and various other allylic azides, rearrangement reactions involving sigmatropic shift of the azido group or photochemical cis-trans isomerization have been investigated, as have base-catalyzed (prototropic) rearrangements to give vinyl azides.
Isotope effect and kinetic studies of the reaction of tertiary alcohols with triphenylphosphine-carbon tetrachloride: Ion pair or concerted?
Dabbagh, Abduol Hossein,Faghihi, Khalil
, p. 3611 - 3617 (2007/10/03)
Kinetics of the reactions of 1,2,3-triphenyl-2-propanol (1), 1,2- diphenyl-2-propanol (2) and 3,3,3-trideuterio-1,2-diphenyl-2-propanol (3) with triphenylphosphine-carbon tetrachloride in the temperature range of 25- 78°C in several solvents are investigated. In a non-polar solvent (CCl4), the reaction of (2) proceeds via intermolecular anti E2 elimination and/or intermolecular SN2 nucleophilic substitution (28% substitution, ratio of 2- alkene/l-alkene=l.06, E/Z>49). In a polar solvent (CH3CN) reaction proceeds via El and/or S(N)1 (24% substitution, 2-alkene/1-alkene=1.9, E/Z≥6. At equilibrium, the ratio of 2-alkene/1-alkene is equal to 99 with E/Z≥4.21. The primary kinetic isotope effect (k(H)/k(D)) for the elimination pathway in the non-polar solvent is equal to 4.90 and 3.90 at temperatures of 25 and 60δC, respectively. A small secondary β-isotope effect of 1.10 was observed for substitution reaction at both temperatures. Direction of substitution (S(N)2 vs. E2) depends on temperature and polarity of the solvent. The energetics (δS(+), δG(+), δH(+)), the rate orders, and optimization of molecular geometry of intermediates by semiempirical methods (AM1 and CNDO) all agree with intermolecular E2 and S(N)2 mechanisms. New rules for stereoselectivity and Hofmann-Saytzeff eliminations are considered. 2000 Elsevier Science Ltd.
New transition-state models and kinetics of elimination reactions of tertiary alcohols over aluminum oxide
Dabbagh,Salehi, J. Mohammad
, p. 7619 - 7627 (2007/10/03)
A new transition-state model was developed in order to justify the anti intramolecular E2 elimination with cis (Z)-preference over pure alumina and interinolecular E2 elimination with trans (E)-preference over doped alumina. The reactions of model compounds 1,2,3-triphenyl-2-propanol (1), 1,2-diphenyl-2-propanol (2), and 3,3,3-trideuterio-1,2-diphenyl-2-propanol (3) with aluminum oxides with a pH range of 4.5-9.5 and thorium oxide in the temperature range of 200-350 °C in 2-hexanol have been investigated. Over acidic alumina (pH = 4.5 ±0.5), the ratio of E-isomer to Z-isomer (E/Z ? 2) for 2 was found to remain unchanged in this temperature range. At 300 °C, however, Saytzeff elimination favored Hofmann. Over pure alumina the E/Z ratio was equal to 0.650 (2-alkene/1-alkene = 0.750). At equilibrium, the E/Z ratio for 2 was equal to 4.5 with the formation of trace amounts of Hofmann adducts. The ratio of Saytzeff to Hofmann elimination was found to be pH independent. Any decrease in pH caused a slight increase in the E/Z ratio. The average primary kinetic isotope effect (kH/kD) for elimination at 230 °C was equal to 3.775 ± 0.227. The ratio of E/Z over thorium oxide at 300 and 350 °C was similar to that of aluminum oxide at 300 °C, but the Saytzeff elimination was surprisingly favored over Hofmann! The energy of activation (Ea), entropy of activation (AS?), selectivity, isotope effect (kH/kD), and semiempirical calculation (AM1) all agreed with concerted E2 elimination.
Nickel(0)-induced geminal bond cleavages leading to carbon-carbon double bonds: Intermediacy of nickel(0)-carbene complexes as a unifying hypothesis
Eisch, John J.,Qian, Yun,Singh, Mona
, p. 207 - 217 (2007/10/03)
The possibility of effecting geminal bond cleavages of organic monomers with nickel(0) complexes to achieve olefinic dimers has been investigated both in stoichiometric reactions between monomers of the type R2CE2 and R2C=E and the complexes (Cod)2Ni, (Et3P)4Ni and (Bpy)(Cod)Ni and in nickel(0)-catalytic α-elimination reactions of α-lithioorganic sulfones, RR′C(Li)(SO2R″). Substrates for the stoichiometric geminal bond cleavages comprised geminal dihalides, aminomethyl sulfides, cyclopropenes, thioketones and ketones. Reductive dimerization to the olefin or its hydroxy derivatives was found to occur to a varying degree in most cases, including the catalytic decomposition of the α-lithioorganic sulfones. Accordingly, this method offers considerable promise in organic synthesis. A gamut of known nickel(0) chemistry, results of chemical-trapping and spectroscopic evidence are marshaled in support of the proposal that such geminal bond cleavages and reductive coupling processes most likely proceed via nickel(0)-carbene intermediates of the type R2C=Ni · Ln.
