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1.
A novel and efficient approach for the synthesis of 1α, 24(R)-dihydroxyvitamin D3 (tacalcitol) starting from readily available enone 1 has been achieved with high stereoselectivity. The key step involved in the synthesis of tacalcitol was the stereoselective reduction of enone 1 using borane as the reducing agent, and the effects of the critical reaction parameters such as temperature, various borane complexes have been examined. Finally, tacalcitol was obtained in five steps from enone 1 with an overall yield of 32% and a ratio of 24-R/S = 95/5. 相似文献
2.
Prof. Dr. Sambasivarao Kotha Ramakrishna Reddy Keesari 《European journal of organic chemistry》2023,26(18):e202300106
Herein, a short synthetic approach to linearly fused tricyclic enone 1 and cis-anti-cis type hydroxy-triquinane 2 has been described in an efficient manner by employing tandem-metathesis as a key step. The triquinane-based enone 1 is prepared by a Babler–Dauben oxidation of hydroxy-triquinane 2 , which is assembled by following a three-step sequence involving a regio- and stereoselective allylation, vinyl Grignard addition, and tandem-metathesis. Our strategy relies on exo-tricyclic ketone, which is derived from readily available exo-dicyclopentadiene-1-one. The newly synthesized molecules were identified and characterized by nuclear magnetic resonance spectroscopy (NMR), and high-resolution mass spectrometry (HRMS) data. It is worth mentioning that tricyclic enone 1 is present as a core unit of many naturally occurring polyquinanes, particularly xeromphalinone family members. Hence, our approach may be useful in the synthesis of such bioactive molecules. 相似文献
3.
G. Yu. Ishmuratov E. R. Latypova P. Ya. Kharisov R. R. Muslukhov A. A. Bannova R. F. Talipov G. A. Tolstikov 《Russian Journal of Organic Chemistry》2008,44(5):652-656
(R)-4-Menthenone compared with common cyclic enones exhibits considerably lower reactivity in 1,4-conjugate addition of organometallic reagents, is inert in Michael reactions and pyrazoline formation evidently due both to the distorted polarization in the enone system and to steric hindrances from the α-isopropyl group in the cyclohexene ring. 相似文献
4.
Gold(I)‐Catalyzed Furan‐yne Cyclizations Involving 1,2‐Rearrangement: Efficient Synthesis of Functionalized 1‐Naphthols and Its Application to the Synthesis of Wailupemycin G
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Dr. Yifeng Chen Dr. Lu Wang Ning Sun Xin Xie Dr. Xiaobo Zhou Haoyi Chen Prof. Yuxue Li Prof. Yuanhong Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12015-12019
Gold‐catalyzed cascade cyclization/1,2‐rearrangement of 1‐(2‐furanyl)phenyl propargyl alcohols has been developed, which provides a rapid and efficient access to multisubstituted 1‐naphthols bearing an enal or enone moiety with high stereoselectivity. The (Z)‐ or (E)‐stereochemistry can be easily controlled by choosing protected‐ or non‐protected substrates. The utility of the methodology has been illustrated in the first total synthesis of wailupemycin G. 相似文献
5.
Pivnenko N. S. Vashchenko V. V. Kutulya L. A. Doroshenko A. O. Chepeleva L. V. 《Russian Chemical Bulletin》2001,50(9):1596-1604
The 1Í NMR method in combination with molecular simulation was used to study conformations of Z- and E-isomers of (1R,4R)-cis-2-(4-methoxyphenyl)benzylidene-p-menthan-3-one. In solutions the Z-isomer, unlike the conformationally uniform Å-isomer, is an equilibrium mixture of chair conformers with the substantial predomination of one form with the axially oriented methyl and equatorial isopropyl groups (75—78%). The enone group is more nonplanar in the Z-isomer than in the Å-isomer. For the isopropyl fragment, the equiprobable existence of trans- and two gauche-rotamers for the Z-isomer and a substantial predomination of gauche-forms in the case of the E-isomer were established. 相似文献
6.
Four‐Component,One‐Pot Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles Bearing 1‐(2‐Phenylselenocyclohexyl) Group
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Wusheng Sheng Shouri Sheng Jiangbo Zeng Zhenzhong Huang Mingzhong Cai 《Journal of heterocyclic chemistry》2014,51(Z1):E222-E226
An efficient, one‐pot, three‐step, regioselective synthesis of 4‐substituted 1‐(2‐phenylselenocyclohexyl)‐1,2,3‐triazoles, involving in situ generation of l‐azido‐2‐phenylselenocyclohexane has been developed via four‐component reaction of phenylselenenyl bromide, cyclohexene, sodium azide and terminal alkynes catalyzed by copper iodide in a mixture of DMF/THF (1:1) at room temperature under mild conditions with simple workup and good yields. 相似文献
7.
Jian Lv Dr. Jiaming Zhang Dr. Zhu Lin Dr. Yongmei Wang Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):972-979
A general enantioselective synthesis of functionalized nitrocyclopropanes by organocatalytic conjugate addition of a variety of bromonitroalkanes to α,β‐unsaturated enone systems is presented. The process, efficiently catalyzed by the salts of 9‐amino‐9‐deoxyepiquinine 1 d serves as a powerful approach to the preparation of synthetically and biologically important cyclopropanes with high levels of enantio‐ and diastereoselectivities. Since only 0.6 equivalents of bromonitromethane are used as a reagent, (S)‐ 2 e is obtained enantiomerically pure by employing chiral 1 d as a highly efficient catalyst for its kinetic resolution (97 % ee at 51 % conversion, selectivity s=120). 相似文献
8.
Irradiation of newly synthesized 2,2-dimethyl-2,3-dihydro-4H-thiin-4-one ( 1 ) in furan affords the two [4 + 2] cycloadducts 3 and 4 and the [2 + 2] cycloadduct 5 in a 5:4:1 ratio (Scheme 1). Irradiation of 1 in MeOH gives a 3:2 mixture of 5- and 6-methoxy-2,2-dimethylthian-4-ones 6 and 7 . Irradiation in CD3OD affords the same (deuterated) adducts with the CD3O and D groups trans to each other, results compatible with cis-addition of MeOH to a trans -configurated ground-state enone. Irradiation of the same enone in furan/MeOH 1:1 gives only the furan cycloadducts 3–5 and no MeOH adducts, suggesting that furan interacts with the (excited) triplet enone before the deactivation of this species to a ground-state (E)-cyclohexenone, which then reacts with MeOH. On irradiation in furan, the corresponding five-membered thiaenone, 2,2-dimethylthiophen-3(2H)-one ( 2 ) affords only one, cis-fused, [4 + 2] cycloadduct with ‘exo’-configuration, i.e. 8 , and 2 does not undergo solvent addition but rather cyclodimerization (→ 9 ) on irradiation in MeOH (Scheme 1). 相似文献
9.
Competitive Gold‐Promoted Meyer–Schuster and oxy‐Cope Rearrangements of 3‐Acyloxy‐1,5‐enynes: Selective Catalysis for the Synthesis of (+)‐(S)‐γ‐Ionone and (−)‐(2S,6 R)‐cis‐γ‐Irone
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Dr. Serena Bugoni Dr. Valentina Merlini Dr. Alessio Porta Dr. Sylvain Gaillard Prof. Giuseppe Zanoni Prof. Dr. Steven P. Nolan Prof. Giovanni Vidari 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(40):14068-14074
We report a simple, highly stereoselective synthesis of (+)‐(S)‐γ‐ionone and (‐)‐(2S,6R)‐cis‐γ‐irone, two characteristic and precious odorants; the latter compound is a constituent of the essential oil obtained from iris rhizomes. Of general interest in this approach are the photoisomerization of an endo trisubstituted cyclohexene double bond to an exo vinyl group and the installation of the enone side chain through a [(NHC)AuI]‐catalyzed Meyer–Schuster‐like rearrangement. This required a careful investigation of the mechanism of the gold‐catalyzed reaction and a judicious selection of reaction conditions. In fact, it was found that the Meyer–Schuster reaction may compete with the oxy‐Cope rearrangement. Gold‐based catalytic systems can promote either reaction selectively. In the present system, the mononuclear gold complex [Au(IPr)Cl], in combination with the silver salt AgSbF6 in 100:1 butan‐2‐one/H2O, proved to efficiently promote the Meyer–Schuster rearrangement of propargylic benzoates, whereas the digold catalyst [{Au(IPr)}2(μ‐OH)][BF4] in anhydrous dichloromethane selectively promoted the oxy‐Cope rearrangement of propargylic alcohols. 相似文献
10.
Cyclohexene, dissolved in benzene is homogeneously oxidised with IrCl(CO)(PPh3)2 as catalyst. No induction period is observed if the concentration of hydroperoxide has a critical value. The reaction rate r increases with the concentration of cyclohexene from r = 1 to 15 mMol O2 l?1 min?1 in pure cyclohexene with turnover numbers of 3000. Product composition is practically independent of the catalyst and cyclohexene concentrations. 相似文献
11.
An efficient and green approach to the synthesis of 2,2′‐arylmethylene bis(3‐hydroxy‐5,5‐dimethylcyclohex‐2‐enone) using L‐histidine as the catalyst is described. In addition, room temperature ionic liquid 1‐butyl‐3‐methylimidazonium tetrafluoroborate [bmim]BF4 was used as green recyclable alternatives to volatile organic solvents for this condensation reaction. This green catalytic system can be recycled several times with no decreases in yields and reaction rates. 相似文献
12.
Summary. Pure (1S,2R,4S)-1,2-epoxy-p-menthan-4-ol and (1R,2S,4R)-1,2-epoxy-p-menthan-4-ol (trans-epoxides of (4S)-terpinen-4-ol and (4R)-terpinen-4-ol) were prepared and certain reactions of these compounds with nucleophilic reagents were studied. It was shown that the Fürst-Plattner rule regarding the trans-diaxial opening of cyclohexene epoxides predicts the predominant products in all cases studied. 相似文献
13.
A. I. Krivoshey N. S. Pivnenko S. V. Shishkina A. V. Turov L. A. Kutulya O. V. Shishkin 《Russian Chemical Bulletin》2006,55(6):999-1009
The spatial structure of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone prepared by photochemical isomerization of the E-isomer was studied by analyzing the magnitudes and temperature dependence of the proton spin-spin coupling constants obtained
by 1H NMR spectroscopy and the results of molecular modeling using semiempirical quantum chemical AM1 and PM3 methods and the
density functional theory (DFT). Comparison of the results obtained for the Z-and E-isomers shows that in both cases the conformational equilibrium for both isomers is characterized by significant preference
of the chair conformer having an equatorial methyl group, namely, − ΔH (chair a ⇌ chair e) = 1.98–2.12 and 1.36–1.54 kcal mole−1 for the Z-and E-isomers, respectively. Distinctions in the non-planarity of the enone fragment and cyclohexanone ring in the Z-and E-isomers under study following from the results of mathematical modeling were confirmed by the experimental values of the
geminal spin-spin coupling constants of protons of the methylene groups in α,α ′-positions with respect to the enone group.
Quantum chemical calculations of the Z-isomer revealed the existence of intramolecular hydrogen bond between the carbonyl oxygen and the nearest aromatic proton
in ortho-position of the benzene ring. Possible reasons for different helical twisting power of (Z)-(5R)-methyl-2-(4-phenylbenzylidene)cyclohexanone and the E-and Z-arylidene derivatives of 1R, 4R-isomenthone in the mesophase are discussed based on the results of molecular structure studies for these compounds.
In the text below the unsaturated ketones under study will be called “arylidene cyclohexanone derivatives” for convenience
of comparing the characteristics of methylcyclohexanone and isomenthone derivatives.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 962–972, June, 2006. 相似文献
14.
《Journal of heterocyclic chemistry》2017,54(2):1252-1260
An efficient protocol is reported for the one‐pot three‐component Bignelli synthesis of a series of 3,4‐dihydropyrimidine‐2(1H )‐ones and thiones in good yields (66–90%) from the aldehydes (4‐benzyloxybenzaldehyde, 5‐bromovanilin, 4‐formyl‐1‐cyclohexene, and trans‐cinnamaldehyde), β‐keto esters (ethyl acetoacetate, allyl acetoacetate, and t‐butyl acetoacetate), and urea/thiourea in ethanol, using nickel chloride hexahydrate as a catalyst. 相似文献
15.
James P. Kutney Peter Grice Krystyna Piotrowska Steven J. Rettig Jerzy Szykula James Trotter Loc Van Chu 《Helvetica chimica acta》1983,66(6):1820-1826
The thujone-derived enone 1 , upon base-catalyzed reaction with 2-methyl-6-vinylpyridine is converted to the pyridine analogue 5 (Scheme 1). Catalytic reduction of the latter to 6 generates two new centers of chirality which eventually become C(8) and C(14) in the ultimate synthetic steroid analogue 12 . An X-ray analysis of 6 establishes the structure and absolute configuration so as to determine its suitability in subsequent synthetic studies. The acetal derivative 7 , via Birch reduction, hydrolysis, and internal aldol cyclization, is converted into the cyclohexenone analogue 10 (Scheme 2). This ‘one-pot’ process affords an efficient conversion of the pyridine ring into a cyclohexenone system required for A-ring construction of the steroid skeleton. Finally, conversion of 10 , via the unsaturated diketone 11 , provides the chiral steroid analogue 12 . 相似文献
16.
The deprotection of 1,3-dibenzyl-5-(N,N-dimethylamino)-6-phenyl-ethyluracil I was investigated. A practical, regioselective N3 deprotection of compound I was performed with excellent yield using cyclohexene as a hydrogen donor. 相似文献
17.
The (2E,4E)‐ and (2E,4Z)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene reacts with aziridine to give aziridinecyclopentenol 3. This product arises from an intermolecular Michael addition of a nitrogen lone pair to the less reactive enone, followed by an intramolecular aldol reaction of the enol with ketone. Furthermore, the initially formed enol did not undergo nucleophilic attack onto the aziridine ring to form heterocycles. Interestingly, the reaction with secondary amine did not give the cyclopentenol adduct, and this only leads to the isomerization of (2E,4Z)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene to the more stable (2E,4E)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene by addition to the more reactive enone. 相似文献
18.
V. D. Kiselev E. A. Kashaeva L. N. Potapova A. I. Konovalov 《Russian Chemical Bulletin》2007,56(3):494-498
The effect of hydrostatic pressure below 1000 kg cm−2 on the rate of reactions of o-and p-nitrophenylsulfenyl chlorides with styrene and cyclohexene was studied. The activation and reaction volumes (cm3 mol−1) for the reactions of o-nitrophenylsulfenyl chloride with styrene in acetonitrile (−23.1 and −23.6), 1,2-dichloroethane (−29.2 and −24.7), chlorobenzene
(no, −20.2), and anisole (−25.1 and −21.2) and for the reaction of p-nitrophenylsulfenyl chloride with styrene in carbon tetrachloride (−39.5±1.5 and −22.0) were determined. In carbon tetrachloride
the activation volumes for the reactions of cyclohexene with o-and p-nitrophenylsulfenyl chlorides (−37.7±2.0 and −40.9±1.2 cm3 mol−1, respectively) are almost the same and coincide with the data for the reactions with styrene. The considerable decrease in
the volume of the transition state in the nonpolar solvent is considered as a consequence of the enhanced electrostriction
of carbon tetrachloride in the solvate sphere of the transition state of the reaction, which excludes the nonpolar transition
state of the sulfuran type.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 477–480, March, 2007. 相似文献
19.
Julia Büker Dr. Baris Alkan Dr. Sonia Chabbra Nikolai Kochetov Tobias Falk Dr. Alexander Schnegg Prof. Dr. Christof Schulz Prof. Dr. Hartmut Wiggers Prof. Dr. Martin Muhler Dr. Baoxiang Peng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(68):16912-16923
La1−xSrxCoO3 (x=0, 0.1, 0.2, 0.3, 0.4) nanoparticles were prepared by spray-flame synthesis and applied in the liquid-phase oxidation of cyclohexene with molecular O2 as oxidant under mild conditions. The catalysts were systematically characterized by state-of-the-art techniques. With increasing Sr content, the concentration of surface oxygen vacancy defects increases, which is beneficial for cyclohexene oxidation, but the surface concentration of less active Co2+ was also increased. However, Co2+ cations have a superior activity towards peroxide decomposition, which also plays an important role in cyclohexene oxidation. A Sr doping of 20 at. % was found to be the optimum in terms of activity and product selectivity. The catalyst also showed excellent reusability over three catalytic runs; this can be attributed to its highly stable particle size and morphology. Kinetic investigations revealed first-order reaction kinetics for temperatures between 60 and 100 °C and an apparent activation energy of 68 kJ mol−1 for cyclohexene oxidation. Moreover, the reaction was not affected by the applied O2 pressure in the range from 10 to 20 bar. In situ attenuated total reflection infrared spectroscopy was used to monitor the conversion of cyclohexene and the formation of reaction products including the key intermediate cyclohex-2-ene-1-hydroperoxide; spin trap electron paramagnetic resonance spectroscopy provided strong evidence for a radical reaction pathway by identifying the cyclohexenyl alkoxyl radical. 相似文献
20.
The kinetics of the reaction by which thallium(III) acetate oxidizes cyclohexene in glacial acetic acid medium, has been studied by UV spectrophotometric observation at 30°C. The consumption of thallium(III) acetate follows a second-order rate law exhibiting first-order dependence on each of thallium(III) acetate and cyclohexene; however, the first-order dependence on cyclohexene disappears at high cyclohexene concentrations as pseudo-first-order conditions prevail above 0.2 M cyclohexene. A steady-state model of the following form is proposed: where Tl, Cy, and Com are units of Thallium(III) acetate, cyclohexene, and a reaction complex. The value of k2 has been evaluated as 0.00027 and (k?1 + k2) as 0.0385k1. For low thallium(III) acetate concentrations the reaction kinetics follow the rate law: where α = the excess concentration of cyclohexene over thallium(III) triacetate. For thallium(III) acetate concentrations above 0.02 M, double salt formation of thallium(III) acetate with product thallium(I) acetate removes thallium(III) acetate from the reaction and a modified rate law is observed. Runge–Kutta numerical solutions to the differential equations provide confirmation that the rate expressions are valid in predicting the observed concentrations of thallium(III) acetate. 相似文献