- Tuning acylthiourea ligands in Ru(II) catalysts for altering the reactivity and chemoselectivity of transfer hydrogenation reactions, and synthesis of 3-isopropoxy-1H-indole through a new synthetic approach
-
Ru(II)-p-cymene complexes (1–3) containing picolyl based pseudo-acylthiourea ligands (L1-L3) were synthesized and characterized. The crystallographic study confirmed the molecular structures of all the ligands (L1-L3) and complex 3. The catalytic activity of the complexes was tested mainly towards TH of carbonyl compounds and nitroarenes. The influence of steric and electronic effects of the ligands on the chemoselectivity and reactivity were reported. The catalytic activity was enhanced and chemoselectivity was switched after tuning the ligands in the catalysts, compared to their corresponding unmodified Ru(II)-p-cymene complexes. The catalysis was extended to a broad range of substrates including some challenging systems like furfural, benzoylpyridine, benzoquinone, chromanone, etc. The strategy of tuning the bifunctional ligands in the catalysts for effective and selective catalysis worked nicely. Further, the catalysis was extended to one pot synthesis of 3-isopropoxyindole from 2-nitrocinnamaldehyde, the first synthetic route similar to Baeyer Emmerling indole synthesis. All the catalytic experiments exhibited high conversion and selectivity.
- Sathishkumar, Pushpanathan N.,Prabha, Padinhattath Sachind,Bhuvanesh, Nattamai S.P.,Karvembu, Ramasamy
-
-
- Photoredox/Cobalt Dual-Catalyzed Decarboxylative Elimination of Carboxylic Acids: Development and Mechanistic Insight
-
Recently, dual-catalytic strategies towards the decarboxylative elimination of carboxylic acids have gained attention. Our lab previously reported a photoredox/cobaloxime dual catalytic method that allows the synthesis of enamides and enecarbamates directly from N-acyl amino acids and avoids the use of any stoichiometric reagents. Further development, detailed herein, has improved upon this transformation's utility and further experimentation has provided new insights into the reaction mechanism. These new developments and insights are anticipated to aid in the expansion of photoredox/cobalt dual-catalytic systems.
- Cartwright, Kaitie C.,Joseph, Ebbin,Comadoll, Chelsea G.,Tunge, Jon A.
-
p. 12454 - 12471
(2020/09/09)
-
- Ru-Photoredox-Catalyzed Decarboxylative Oxygenation of Aliphatic Carboxylic Acids through N-(acyloxy)phthalimide
-
Decarboxylative aminoxylation of aliphatic carboxylic acid derivatives with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) in the presence of ruthenium photoredox catalysis is reported. The key transformation entails a highly efficient photoredox catalytic cycle using Hantzsch ester as a reductant. The ensuing alkoxyamine can be readily converted to the corresponding alcohol in one pot, representing an alternative approach to access aliphatic alcohols under photoredox conditions.
- Zheng, Chao,Wang, Yuting,Xu, Yangrui,Chen, Zhen,Chen, Guangying,Liang, Steven H.
-
p. 4824 - 4827
(2018/08/24)
-
- Construction of bicyclic systems containing an oxygen bridge by isomerization of cyclic epoxy alcohols
-
A novel method for constructing a 7-oxabicyclo[2.2.1]heptane skeleton was developed. The substrates, namely cis-3,4-epoxy-1-cyclohexanol derivatives, were prepared from the corresponding 3-cyclohexen-1-ol derivatives via a stereoselective epoxidation reaction using a vanadium catalyst. Upon heating with lithium iodide in propionitrile, the cis-epoxy alcohol was transformed into the 7-oxabicyclo[2.2.1]heptane derivative in high yield. The reaction proceeds through formation of a lithium alkoxide bearing an iodohydrin moiety, followed by an intramolecular SN2 reaction.
- Iwakura, Masaru,Tokura, Hiroshi,Tanino, Keiji
-
p. 1223 - 1226
(2017/03/02)
-
- Stereoselective Synthesis of 7-(E)-Arylidene-2-chloro-6-azabicyclo[3.2.1]octanes via Aluminum Chloride-Promoted Cyclization/Chlorination of Six-Membered Ring 3-Enynamides
-
An efficient stereoselective synthesis of 7-(E)-arylidene-2-chloro-6-azabicyclo[3.2.1]octanes is described. The aluminum chloride-promoted cyclization/chlorination of six-membered ring 3-enynamides enables a straightforward approach to the 6-azabicyclo[3.2.1]octane nucleus that is incorporated in many biologically active compounds. Acid treatment of the resultant chlorinated arylideneazabicyclooctanes furnishes 3-alkanoyl-4-chlorocyclohexanamines in excellent yields and high stereoselectivity. (Figure presented.).
- Yeh, Ming-Chang P.,Chang, Yi-Mei,Lin, Hsin-Hui
-
supporting information
p. 2196 - 2201
(2017/07/07)
-
- Highly Enantioselective Construction of Hajos-Wiechert Ketone Skeletons via an Organocatalytic Vinylogous Michael/Stetter Relay Sequence
-
A highly enantioselective supramolecular iminium-catalyzed vinylogous Michael addition/Stetter relay sequence has been developed. This transformation provided a series of Hajos-Wiechert-type fused bicyclic diones with three continuous stereogenic centers in good yields with excellent enantioselectivities. The obtained products can be easily transformed into other structures with potential synthetic value.
- Jia, Zhi-Long,Wang, Yao,Zhao, Chuan-Gang,Zhang, Xiao-Hai,Xu, Peng-Fei
-
supporting information
p. 2130 - 2133
(2017/04/27)
-
- SULFIDE ALKYL COMPOUNDS FOR HBV TREATMENT
-
The present invention includes a method of inhibiting, suppressing or preventing HBV infection in an individual in need thereof, comprising administering to the individual a therapeutically effective amount of at least one compound of the invention.
- -
-
Paragraph 0505
(2016/06/28)
-
- Parallel and competitive pathways for substrate desaturation, hydroxylation, and radical rearrangement by the non-heme diiron hydroxylase AlkB
-
A purified and highly active form of the non-heme diiron hydroxylase AlkB was investigated using the diagnostic probe substrate norcarane. The reaction afforded C2 (26%) and C3 (43%) hydroxylation and desaturation products (31%). Initial C-H cleavage at C2 led to 7% C2 hydroxylation and 19% 3-hydroxymethylcyclohexene, a rearrangement product characteristic of a radical rearrangement pathway. A deuterated substrate analogue, 3,3,4,4-norcarane-d 4, afforded drastically reduced amounts of C3 alcohol (8%) and desaturation products (5%), while the radical rearranged alcohol was now the major product (65%). This change in product ratios indicates a large kinetic hydrogen isotope effect of ~20 for both the C-H hydroxylation at C3 and the desaturation pathway, with all of the desaturation originating via hydrogen abstraction at C3 and not C2. The data indicate that AlkB reacts with norcarane via initial C-H hydrogen abstraction from C2 or C3 and that the three pathways, C3 hydroxylation, C3 desaturation, and C2 hydroxylation/radical rearrangement, are parallel and competitive. Thus, the incipient radical at C3 either reacts with the iron-oxo center to form an alcohol or proceeds along the desaturation pathway via a second H-abstraction to afford both 2-norcarene and 3-norcarene. Subsequent reactions of these norcarenes lead to detectable amounts of hydroxylation products and toluene. By contrast, the 2-norcaranyl radical intermediate leads to C2 hydroxylation and the diagnostic radical rearrangement, but this radical apparently does not afford desaturation products. The results indicate that C-H hydroxylation and desaturation follow analogous stepwise reaction channels via carbon radicals that diverge at the product-forming step.
- Cooper, Harriet L. R.,Mishra, Girish,Huang, Xiongyi,Pender-Cudlip, Marilla,Austin, Rachel N.,Shanklin, John,Groves, John T.
-
supporting information
p. 20365 - 20375
(2013/02/25)
-
- A homogeneous gallium(III) compound selectively catalyzes the epoxidation of alkenes
-
We demonstrate that a simple gallium(III) complex, [Ga(phen) 2Cl2]Cl (phen = 1,10-phenanthroline), can serve as a homogeneous catalyst for the epoxidation of alkenes. The olefin epoxidations proceed relatively quickly at mild temperatures and, under optimum conditions, are highly selective for the epoxide product.
- Jiang, Wenchan,Gorden, John D.,Goldsmith, Christian R.
-
body text
p. 2725 - 2727
(2012/04/23)
-
- Hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine
-
Non-heme iron halogenases, such as SyrB2 and CytC3, catalyze the regioselective chlorination and bromination of aliphatic C-H bonds. Reported here is the hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen). The reactions between these coordination compounds and meta-chloroperbenzoic acid generate oxidants capable of oxidizing weak C-H bonds to C-Cl bonds. This chemistry is regioselective, with a strong preference for activating C-H bonds on secondary carbons over weaker C-H bonds on tertiary carbons. The reactivity is consistent with the methyl groups on the ligands preventing more sterically encumbered substrates from accessing the reactive portions of a [MIV(LMen)(O)Cl2] oxidant. The iron compounds promote more hydrocarbon chlorination than their manganese analogs.
- Goldsmith, Christian R.,Coates, Cristina M.,Hagan, Kenton,Mitchell, Casey A.
-
body text
p. 24 - 30
(2011/04/22)
-
- Rate coefficients and products for gas-phase reactions of chlorine atoms with cyclic unsaturated hydrocarbons at 298 K
-
Rate coefficients for the reaction of Cl atoms with cycloalkenes have been determined using the relative rate method, at 298 K and atmospheric pressure of N2. Reference molecule was n -hexane, and the concentrations of the organics were followed by gas chromatographic analysis. Cl atoms were prepared by photolysis of trichloroacetyl chloride at 254 nm. The relative rates of reactions of Cl atoms with cycloalkenes, with, respect to M-hexane, are measured as 1.12 ±0.38, 1.31 ±0.14, and 1.69±0.18forcyclopentene, cyclohexene, and cycloheptene, respectively. Considering the absolute value of the rate coefficient of the reaction of Cl atom with n-hexane as 3.03 ± 0.06 × 10-10 cm3 molecule-1 s -1, the rate coefficient values for cyclopentene, cyclohexene, and cycloheptene are calculated, to be (3.39 ± 1.08) × 10 -10, (3.97 ±0.43) × 10-10, and (5.12 ± 0.55) × 10-10 cm3 molecule-1 S -1', respectively. The experiments for each, molecule were repeated six to eight times, and the slopes and the rate coefficients given above are the average values of these measurements, and the quoted error includes 2σ as well as all other uncertainties in the measurement and calculations. The rate coefficient increases linearly with the number of carbon atoms, with an increment per additional CH2 group being (8.7 ± 1.6) × 11-12 cm3 molecule-1 s-1. Chloroketones and chloroalcohols, along with unsaturated, ketones and alcohols, were found to be the major products of Cl-atom-initiated oxidation of cycloalkenes in the presence of air. The atmospheric implications of these results are discussed, along with a comparison with the reported structure activity relationships.
- Sharma,Pushpa,Dhanya,Naik,Bajai
-
body text
p. 98 - 105
(2011/06/21)
-
- Cage escape competes with geminate recombination during alkane hydroxylation by the diiron oxygenase AlkB
-
(Chemical Presented) AlkBstops the radical clock: Three structurally analogous radical-clock substrates with a large span in their rearrangement rates are hydroxylated by AlkB to afford similar amounts of rearranged (2) and unrearranged products (1). Such a result is in accord with radical rebound competing with cage escape of the geminate substrate radical. The results show that radical clocks can measure both the radical lifetime and the kinetics of cage escape.
- Austin, Rachel N.,Luddy, Kate,Erickson, Karla,Pender-Cudlip, Marilla,Bertrand, Erin,Deng, Dayi,Buzdygon, Ryan S.,Van Beilen, Jan B.,Groves, John T.
-
supporting information; experimental part
p. 5232 - 5234
(2009/04/04)
-
- Radical intermediates in monooxygenase reactions of Rieske dioxygenases
-
Rieske dioxygenases catalyze the cis-dihydroxylation of a wide range of aromatic compounds to initiate their biodegradation. The archetypal Rieske dioxygenase naphthalene 1,2-dioxygenase (NDOS) catalyzes dioxygenation of naphthalene to form (+)-cis-(1R,2S
- Chakrabarty, Sarmistha,Austin, Rachel N.,Deng, Dayi,Groves, John T.,Lipscomb, John D.
-
p. 3514 - 3515
(2007/10/03)
-
- A practical and scaleable synthesis of 1r,5s-bicyclo[3.1.0]hexan-2-one: The development of a catalytic lithium 2,2,6,6-tetramethylpiperidide (LTMP) mediated intramolecular cyclopropanation of (R)-1,2-epoxyhex-5-ene
-
An efficient synthesis of 1R,5S-bicyclo[3.1.0]hexan-2-one from (R)-1,2-epoxyhex-5-ene is described. Development of a catalytic intramolecular cyclopropanation of (R)-1,2-epoxyhex-5-ene gives the key homochiral bicycle[3.1.0]hexan-1-ol, which is then oxidized to the desired ketone. This process has been successfully demonstrated on a multi-kilogram scale.
- Alorati, Anthony D.,Bio, Matthew M.,Brands, Karel M. J.,Cleator, Ed,Davies, Antony J.,Wilson, Robert D.,Wise, Chris S.
-
p. 637 - 641
(2012/12/31)
-
- The diagnostic substrate bicyclohexane reveals a radical mechanism for bacterial cytochrome P450 in whole cells
-
(Figure Presented) On home ground: The reaction mechanisms of bacterial alkane-oxidizing cytochrome P450s were determined in their native environment using a novel diagnostic substrate probe, bicyclohexane, in whole cells and cell-free extracts (see picture). Purified P450cam also oxidizes bicyclohexane. Clear evidence for a substrate-based radical with a lifetime of 75-250 ps was obtained.
- Austin, Rachel N.,Deng, Dayi,Jiang, Yongying,Luddy, Kate,Van Beilen, Jan B.,Ortiz De Montellano, Paul R.,Groves, John T.
-
p. 8192 - 8194
(2008/02/08)
-
- Asymmetric synthesis of cyclic β-hydroxyallylsilanes via sequential allyltitanation-ring closing metathesis
-
Highly enantioenriched cyclic β-hydroxyallylsilanes have been prepared via enantioselective allylation of unsaturated aldehydes using a chiral allyltitanium reagent, followed by a ring-closing metathesis. Functionalized rings of various sizes have been sy
- Adam, Jean-Michel,De Fays, Laurence,Laguerre, Michel,Ghosez, Léon
-
p. 7325 - 7344
(2007/10/03)
-
- Sequential ring-closing metathesis/Pd-catalyzed, Si-assisted cross-coupling reactions: General synthesis of highly substituted unsaturated alcohols and medium-sized rings containing a 1,3-cis-cis diene unit
-
A sequential ring-closing metathesis/silicon-assisted cross-coupling protocol has been developed. Alkenyldimethylsilyl ethers of allylic, homoallylic and bis(homoallylic) alcohols undergo facile ring closure with Schrock's catalyst to afford 5-, 6-, and 7-membered cycloalkenylsiloxanes, respectively, in some cases with substituents on both alkenyl carbons. These siloxanes are highly effective coupling partners that afford styrenes and dienes (with various aryl and alkenyl halides) in high yield and specificity as well as good functional group compatibility. The siloxanes bearing a Z-iodoalkenyl tether undergo an intramolecular coupling process in the presence of [allylPdCl] 2 which constitutes a powerful method for the construction of medium-sized rings with an internal 1,3-cis-cis diene unit. The formation of 9-, 10-, 11-, and 12-membered carbocyclic dienes is achieved in good yield. Extension to the synthesis of 9-membered ring unsaturated ethers has also been accomplished. Noteworthy features of this process include: (1) highly stereospecific intramolecular coupling, (2) flexible positioning of the revealed hydroxy group, and (3) potential extension to other medium-sized carbocycles and heterocycles. Graphical Abstract.
- Denmark, Scott E.,Yang, Shyh-Ming
-
p. 9695 - 9708
(2007/10/03)
-
- Scope of the directed dihydroxylation: Application to cyclic homoallylic alcohols and trihaloacetamides
-
The synthesis and directed dihydroxylation of a range of cyclic alkenes was investigated. Both homoallylic alcohols and homoallylic trihaloacetamides were found to be efficient directing groups, giving rise to good to excellent levels of remote asymmetric induction with OsO4-TMEDA. Interestingly, in all cases examined, trifluoroacetamides were found to be superior to trichloroacetamides as directing groups and an argument is presented which rationalises this observation.
- Donohoe, Timothy J.,Mitchell, Lee,Waring, Michael J.,Helliwell, Madeleine,Bell, Andrew,Newcombe, Nicholas J.
-
p. 2173 - 2186
(2007/10/03)
-
- Intramolecular silicon-assisted cross-coupling reactions: General synthesis of medium-sized rings containing a 1,3-cis-cis diene unit
-
The combination of ring-closing metathesis and Pd-catalyzed, silicon-assisted intramolecular cross-coupling has been developed to provide an effective and powerful method for construction of medium-sized rings with an internal 1,3-cis-cis diene unit. Allylic alcohols bearing a Z-iodoalkenyl tether can be silylated with chlorodimethylvinylsilane and subjected to Mo-catalyzed ring-closing metathesis to form unsaturated siloxanes. Activation of the siloxane with tetrabutylammonium fluoride in the presence of [allylPdCl]2 leads to high yielding ring-closing reactions to form 9-, 10-, 11- and 12-membered rings. Extension to the synthesis of 9-membered ring unsaturated ethers has also been accomplished. Noteworthy features of this process include: (1) a highly stereospecific intramolecular coupling process, (2) flexible positioning of the hydroxy group, and (3) potential extension to other medium-sized carbocycles and heterocycles. Copyright
- Denmark, Scott E.,Yang, Shyh-Ming
-
p. 2102 - 2103
(2007/10/03)
-
- Iridium-catalyzed transfer hydrogenation of α,β-unsaturated and saturated carbonyl compounds with 2-propanol
-
The selective transfer hydrogenation of α,β-unsaturated carbonyl compounds to saturated ones was achieved by the use of 2-propanol as a hydrogen donor under the influence of catalytic amounts of [Ir(cod)Cl]2, 1,3-bis(disphenylphosphino)propane (dppp), and Cs2CO3. Thus, a variety of conjugated enones were allowed to react with 2-propanol in the presence of the [Ir(cod)Cl]2/dppp/Cs2CO3 system to give the corresponding saturated carbonyl compounds in good to excellent yields without formation of allylic alcohols. Both dppp and Cs2CO3 were essential components to achieve the reduction satisfactorily. Additionally, the reduction of carbonyl compounds to alcohols was also promoted by the same catalytic system. When the reaction of a 1:1 mixture of a conjugated ketone and a saturated ketone with 2-propanol was carried out in the presence of [Ir(cod)Cl]2 combined with dppp and Cs2CO3, the reduction of the α,β-unsaturated ketone was found to take place in preference to that of the saturated ketone.
- Sakaguchi,Yamaga,Ishii
-
p. 4710 - 4712
(2007/10/03)
-
- Oxidation with the "O2 - H2O2 - Vauauium complex - Pyrazine-2-carboxylic acid" reagent 9. Oxidation of cyclohexene and decalin
-
The oxidation of cyclohexene with hydrogen peroxide catalyzed by a vanadium complex and pyrazine-2-carboxylic acid (PCA) in air results in the formation of cyclohex-2-enyl hydroperoxide as the main product and cyclohex-2-enol, cyclohex-2-enone, cyclohex-3-enyl hydroperoxide, cyclohex-3-enol, cyclohexanol, cyclohexane, and 1,2-epoxycyclohexane in lesser amounts. The composition of the products of oxidation of decalin isomers with the system in question is similar to those obtained in the photochemical oxidation with hydrogen peroxide in air and in the oxidation with air in the presence of anthraquinone. A proposed mechanism for the oxidation includes the initiation by hydroxyl radicals generated from hydrogen peroxide under the action of the V - PCA system.
- Schuchardt,Guerreiro,Shul'pin
-
p. 247 - 252
(2007/11/27)
-
- Syntheses with organoboranes. VII, monohydroboration of conjugated dienes with catecholborane catalyzed by complexes of Nickel(II) chloride and Cobalt(II) chloride with diphosphines
-
The monohydroboration of representative conjugated dienes 1-7 with catecholborane in the presence of SmI3, t-BuOSmI2, LaI3, Ti(OPr(i))4, iron(II), nickel(II) and cobalt(II) chloride complexes with dppe, dppp and dppb was examined. NiCl2(dppe), NiCl2(dppp) and CoCl2(dppp) shoned catalytic activity. The 1,2-addition products were obtained, no 1,4-addition was observed. The reactivity in the presence of NiCl2(dppe) decreased in the order acyclic dienes > cyclic dienes >>1-decene.
- Zaidlewicz, Marek,Meller, Jerzy
-
p. 7279 - 7282
(2007/10/03)
-
- Synthesis and inhibitory properties of (1R,2R,4R,6R)-6-O-(2-hydroxyethyl)cyclohexane-1,2,4,6-tetraol derivatives: Mechanistic probes for the inositol monophosphatase reaction
-
The phosphate derivatives 2, 3 and 4 of 6-O-(2-hydroxyethyl)cyclohexane-1,2,4,6-tetraol have been designed to inhibit inositol monophosphatase, the putative target for lithium therapy, by interacting simultaneously with both cofactor metal ions at the active site of the enzyme. The compounds have been synthesised, via the known key common intermediate cyclohexene oxide, from cyclohexane-1,4-diol in moderate yield, and have been tested for activity in standard enzyme assays. Each compound serves as a competitive inhibitor and displays the expected inhibitory properties. Indeed, compound 4 and the cyclic phosphate 3 of 6-O-(2-hydroxyethyl)cyclohexane-1,2,4,6-tetraol are, respectively, the most potent examples of a primary alkyl phosphate inhibitor and a phosphate monoanion inhibitor yet reported for the enzyme. The stereochemistry of the most potent inhibitor, (1R,2R,4R,6R)-2 as deduced from the X-ray crystal structure of a synthetic precursor, provides useful mechanistic insight into the action of the enzyme and the mode of inhibitor binding.
- Schulz, Juergen,Gani, David
-
p. 657 - 670
(2007/10/03)
-
- Synthesis and structure-opioid activity relationships of trans-(±)-3,4-Dichloro-N-methyl-N-[4- or 5-hydroxy-2-(1-pyrrolidiny)cyclohexyl]benzeneacetamides
-
To explore the effects of attaching a hydroxy function to the cyclohexane ring of κ-selective opioid N-[2-(1-pyrrolidinyl)cyclohexyl]benzeneacetamides trans-(±)-3,4-dichloro-N-methyl-N-[4- or 5-hydroxy-2-(1-pyrrolidiny)cyclohexyl]benzeneacetamides (1-4) a
- Cheng, Chen-Yu,Chen, Chin-Yuan,Tao, Pao-Luh
-
p. 835 - 842
(2007/10/03)
-
- Solvent induced isomerization of 2-cyclohexen-1-ol to 3-cyclohexen-1-ol by a chiral lithium amide
-
Enantioselective deprotonation by lithium (S)-1-(2-pyrrolidinylmethyl)pyrrolidine 1 of cyclohexene oxide 2 on changing the solvent from tetrahydrofuran (THF) to cis-2,5-dimethyl-THF (cis-DMTHF) gives the homoallylic alcohol 3-cyclohexen-1-ol 4 up to 74% yield as isomerized product besides the 2-cyclohexen-1-ol 3. In the mixed solvent (THF/cis-DMTHF) 4 was isolated up to 51% yield (25% ee for (S)-4) and 3 in 42% yield (66% ee for (S)-3). In a separate experiment racemic 3 isomerized to racemic 4 in 74% yield when excess of 1 in DMTHF was used.
- Khan, Agha Zul-Qarnian,Arvidsson, Per I.,Ahlberg, Per
-
p. 399 - 402
(2007/10/03)
-
- Mechanism of the 1,3-sigmatropic shift of 2-vinylcyclobutanol alkoxides
-
The rate of rearrangement of 2-vinylcyclobutanol was studied in dimethyl sulfoxide and tetrahydrofuran solvents. Rearrangement to 3-cyclohexenol in 1% aqueous DMSO is catalyzed by lithium hydroxide. When lithium bromide is added to this medium, the rate i
- Harris, Nathan J.,Gajewski, Joseph J.
-
p. 6121 - 6129
(2007/10/02)
-
- NOVEL AND FACILE REDUCTION OF PHENOL DERIVATIVES WITH SAMARIUM DIIODIDE-BASE SYSTEM
-
Phenol was rapidly reduced with samarium diiodide-base system in the presence of protic solvent at room temperature to afford 3-cyclohexen-1-ol accompanied by cyclohexanol.The similar reduction of 4-methoxyphenol and 2-naphthol gave 4-hydroxycyclohexanone and 1,2,3,4-tetrahydro-2-naphthol in excellent yield, respectively.
- Kamochi, Yasuko,Kudo, Tadahiro
-
p. 4169 - 4172
(2007/10/02)
-
- Small Molecule Analogs of Phospholipid-Metal Ion Binding Sites: Synthesis and Molecular Modeling of Cyclohexane-1,2,4-triol Triphosphates
-
Four diastereomeric cyclohexane-1,2,4-triol triphosphates were synthesized to serve as small molecule analogs of putative phospholipid-metal ion binding sites. The parent cyclohexane-1,2,4-triols were prepared and phosphorylated. Deprotection of the tris(
- Amburgey, Judith C.,Shuey, Steven W.,Pedersen, Lee G.,Hiskey, Richard G.
-
p. 172 - 197
(2007/10/02)
-
- Homolytic Displacement at Saturated Carbon: Part 5. Synthesis of Cyclopropylmethyl, Bicyclohex-2-yl, Bicyclohept-2-yl and Cyclohexanespirocycloprop-2-yl Sulphones from the Corresponding But-3-enylcobaloximes
-
But-3-enylcobaloxime reacts with arenesulphonyl chlorides under thermal and photochemical conditions to give cyclopropylmethyl sulphones.The yields depend upon the reaction conditions used.Similar reactions of cyclopent-2-enylmethylcobaloxime and cyclohex-2-enylmethylcobaloximes under photochemical conditions form a mixture of cis and trans isomers of bicyclohex-2-yl and bicyclohept-2-yl sulphones in (50:50) and (70:30) isomeric ratios respectively.However, cyclohex-3-enylcobaloximes form only the trans-bicyclohex-2-yl sulphone.Exclusive formation of cycloalkanespirocycloprop-2-yl sulphones is observed in the reactions of 2-(cyclo alk-1-enyl)ethylcobaloximes with arenesulphonyl chlorides.The reactions are free radical in nature and are believed to take place by a chain mechanism.In the key step a homolytic attack of the RSO2 radical at the terminal (δ) carbon of the butenyl ligand leads to the cyclized product.The exact nature of the ring closure step is uncertain, as both concerted and stepwise mechanisms are possible.
- Gupta, B. Dass,Das, Indira,Dixit, Vandana
-
p. 2409 - 2446
(2007/10/02)
-
- Acid-Catalyzed Hydrolysis of Bridged Bi- and Tricyclic Compounds. XXX. 7-Oxabicycloheptane: Kinetics and Mechanism
-
7-Oxabicycloheptane (7-oxanorbornane) produces in concentrated (5.5 - 7.0 mol dm-3) aqueous perchloric acid mainly 3-cyclohexen-1-ol and a mixture (1:1) of cis- and trans-1,4-cyclohexanediols.The activation entropy, the solvent deuterium isotope effect and the slope parameter m(excit.) of the linear excess acidity plot as well as the products are in agreement with the A-1 hydrolysis mechanism.The data are compared with those recently measured for 7-oxa-5-oxo-2-bicycloheptene.
- Lajunen, Martti,Uotila, Riikka
-
p. 968 - 971
(2007/10/02)
-
- Palladium-catalyzed allylic acetoxylation: an exploratory study of the influence of added acids
-
In order to investigate the possibility of improving the selectivity in palladium-catalyzed acetoxylation of substituted cycloalkenes and linear alkenes, the influence of added strong acids has been studied.It was found that the product selectivity can be increased in some cases, but also that side reactions lower the total yields when trifluoroacetic or stronger acids are used.The improvement of the selectivity may possibly be due to a change in mechanism for the acetoxylation.
- Akermark, Bjoern,Hansson, Sverker,Rein, Tobias,Vagberg, Jan,Heumann, Andreas,Baeckvall, Jan-Erling
-
p. 433 - 444
(2007/10/02)
-
- ORGANOTINS AS ETHERIFICATION CATALYSTS. III. ETHERIFICATIONS AND HYDRO-HYDROXY-ELIMINATIONS PROMOTED BY BUTYLTIN TRICHLORIDE
-
Butyltin trichloride, as a catalyst precursor, promotes the following processes: (i) etherification of 2,3-unsaturated alcohols, (ii) etherification of functional diols, (iii) cyclization of 2,5-hexanedione, and (iv) dehydration of cyclic diols.Many examples are reported.
- Marton, Daniele,Slaviero, Pierangelo,Tagliavini, Giuseppe
-
p. 7099 - 7108
(2007/10/02)
-
- A MEERWEIN-PONNDORF-VERLEY TYPE REDUCTION OF α,β UNSATURATED KETONES TO ALLYLIC ALCOHOLS CATALYZED BY MgO
-
Allylic alcohols are obtained with an unprecedented simple method by chemoselective hydrogen transfer reduction of α,β unsaturated ketones catalyzed by MgO.
- Kaspar, J.,Trovarelli, A.,Lenarda, M.,Graziani, M.
-
p. 2705 - 2706
(2007/10/02)
-
- SYNTHESIS OF Z-ALLYLIC ACETATES VIA FRAGMENTATION OF CYCLIC HOMOALLYLIC ALCOHOLS
-
Z-Allylic acetates (6a-6e) having an additional functional group as ketone or aldehyde were prepared via the fragmentation of the homoallylic alcohols (5a-5e) in the presence of lead tetraacetate.
- Ramaiah, P.,Rao, A. S.
-
p. 2119 - 2120
(2007/10/02)
-
- The Reactions of Hydroxyl Radicals with 1,4- and 1,3-Cyclohexadiene in Aqueous Solution. A Pulse Radiolysis and Product Study
-
The reactions of radiolytically generated hydroxyl radicals and H atoms with 1,4- and 1,3-cyclohexadiene were studied by pulse radiolysis and product analysis.Hydrogen abstraction from these substrates by the OH radical yields the cyclohexadienyl radical (ε (310 nm) = 4400 dm3 mol-1 cm-1 from the reaction of the H atom with benzene) with an efficiency of 50percent (0.29 μmol J-1) in the case of 1,4-cyclohexadiene and 25percent (0.15 μmol J-1) in the case of 1,3-cyclohexadiene as determined by pulse radiolysis.The remaining OH radicals add to the olefin.In 1,4-cyclohexadiene the yield of the resulting adduct radicals has been determined in a steady-state 60Co-γ-irradiation experiment by reducing it with added 1,4-dithiothreitol (DTT) to 4-hydroxycyclohexene.There are two sites of OH radical attack in the case of 1,3-cyclohexadiene, and only the alkyl radical is reduced quantitatively by DTT (G(3-hydroxycyclohexene) = 0.15 μmol J-1).From material balance considerations it is concluded that the allylic radical must be formed with a G value of 0.28 μmol J-1 but largely escapes reduction by DTT (G(4-hydroxycyclohexene) = 0.03 μmolJ-1).H atom add preferentially to the double bonds of 1,4- and 1,3-cyclohexadiene (78percent and 93percent, respectively), while the O(-) radical (the basic form of the OH radical) undergoes mainly H-abstraction (92percent and 83percent, respectively).The radicals formed in these systems decay bimolecularly (2k = 2.8E9 dm3 mol-1 s-1).In their combination reactions the cyclohexadienyl radicals form the four possible dimers in proportions such that the dienyl radical moiety shows a 2:1 preference to react from its central (1a) rather than from a terminal carbon atom (1b).Cyclohexadienyl radicals and the OH- and H-adduct radicals also cross-terminate by disproportionation and dimerization.Material balance has been obtained for the 1,4-cyclohexadiene system in N2O-saturated solution (E-2 mol dm-3) at a dose rate of 0.14 Gy s-1, the products (G values in μmol J-1) being: benzene (0.085), 4-hydroxycyclohexene (0.25), cyclohexadienyl-dimers (0.144), cyclohexadienyl-OH-adduct-dimers (0.02).Some of the 4-hydroxycyclohexene is formed in an H-abstraction reaction by the OH-adduct radical from 1,4-cyclohexadiene. - Keywords: 1,4-Cyclohexadiene, 1,3-Cyclohexadiene, Hydroxyl Radical, Cyclohexadienyl Radical, Pulse Radiolysis
- Pan, Xian-Ming,Bastian, Eugenie,Sonntag, Clemens von
-
p. 1201 - 1205
(2007/10/02)
-
- Conformational Analysis by Thermal Variation of Rotatory Power. Monosubstituted Cyclohexene Enantiomers
-
The conformer rotatory powers of six 4-substituted cyclohexenes have been calculated by extension of the Brewster procedure and used to estimate the conformational free energy differences.The corresponding conformational rotivities are utilized to analyze
- Lauricella, Robert,Kechayan, Josette,Bodot, Hubert
-
p. 1577 - 1582
(2007/10/02)
-
- Hydroboration. 76. Hydroboration of Cyclic Dienes with Representative Hydroborating Agents
-
A detailed study was made of the hydroboration of cyclic dienes with representative hydroborating agents: borane-methyl sulfide (BMS), 9-borabicyclononane (9-BBN), disiamylborane (Sia2BH), dibromo-borane-methyl sulfide (Br2BH*SMe2), and dibromoborane (Br2BH). 1,4-Cyclohexadiene essentially undergoes monohydroboration with a stoichiometric amount of the representative hydroborating agents, whereas 1,5-cyclooctadiene gives the dihydroboration product predominantly.The rapid dimerization of 1,3-cyclopentadiene introduces a complication into its hydroboration.However, monomeric cyclopentadiene undergoes hydroboration primarily to the homoallylic derivative with little of the desired allylic product.Hydroboration of 1,3-cyclohexadiene with a stoichiometric amount of the hydroborating agent furnishes mainly the allylboranes, which upon treatment with acetaldehyde followed by oxidation, furnishes 1-(2-cyclohexenyl)-1-ethanol in good yield.Similary, hydroboration of 1,3-cycloheptadiene and 1,3-cyclooctadiene furnished dihydroborated products preferentially, with lower yields of the corresponding allylboranes, characterized as 1-(2-cycloheptenyl)-1-ethanol and 1-(2-cyclooctenyl)-1-ethanol, respectively, following reaction with acetaldehyde.
- Brown, Herbert C.,Bhat, Krishna S.
-
p. 445 - 449
(2007/10/02)
-
- HOMOLYTIC DISPLACEMENT AT CARBON. X. TOLUENESULPHONYL IODIDE AS A SOURCE OF TOLUENESULPHONYL RADICALS FOR THE FORMATION OF ALLYL-, BENZYL-, CYCLOPROPYLCARBINYL-, SPIROCYCLOPROPYLCYCLOALKYL-, BICYCLOALKYL-, AND BICYCLOALKYL-4-TOLYLSULPHONES FROM ORGANOCOBALOXIMES
-
4-Toluenesulphonyl iodide reacts thermally at alkylsulphone.Spiro- and bicyclo-alkyl compounds are also formed with other free radical precursors.The reactions are believed to take place through a chain mechanism in which cobaloxime(II), present adventitiously or formed by partial homolysis of the substrate, abstracts iodine from the toluenesulphonyl iodide to give the toluenesulphonyl radical, which attacks the organic ligand of the cobaloxime, preferably at the terminal olefinic carbon, thereby displacing cobaloxime(II) and giving the observed organic product.
- Ashcroft, Martyn R.,Bougeard, Peter,Bury, Adrian,Cooksey, Christopher J.,Johnson, Michael D.
-
p. 403 - 416
(2007/10/02)
-
- Factors Influencing Conformational Preferences in Cyclohexenes
-
Conformational preferences have been measured for the first time for 4-substituted cyclohexenes in a solvent of low polarity.Measurements were made for the substituents Cl, Br, I, OH, OSiMe3, and CN and were compared with conformational preferences in cyclohexyl and exo-methylenecyclohex-3-yl.In the nearly nonpolar solvent CF2Cl2, in which intramolecular interactions are maximized, there is a much larger axial population for cyclohexen-4-yl than in cyclohexyl or exo-methylenecyclohex-3-yl.In particular, the dipolar interaction of the endocyclic double bond is reduced from that of the exocyclic double bond.This observation is confirmed by the almost negligible effect of symmetrizing the endocyclic double bond through 1,2-dimethyl substitution, in contrast with the large effect of symmetrizing the exocyclic double bond through 7,7-dimethyl substitution.Polar solvents increase the proportion of the axial conformer to a smaller extent for the endocyclic than for the exocyclic system, again in agreement with a lower dipolar effect in the endocyclic case.These results emphasize the anisotropic nature of the steric effects of double bonds.
- Lambert, Joseph B.,Marko, Dale E.
-
p. 7978 - 7982
(2007/10/02)
-
- MECHANISMS OF EPOXIDATIONS AND CHLORINATIONS OF HYDROCARBONS BY INORGANIC HYPOCHLORITE IN THE PRESENCE OF A PHASE-TRANSFER CATALYST.
-
Inorganic hypochlorite in the presence of a quarternary ammonium salt (phase-transfer catalyst) not only epoxidizes several arenes to arene oxides in high yields but also converts toluene to alpha -chlorotoluene, anisole to ring chlorinated anisoles, and alkenes to a complex mixture of chlorinated and oxidized products, including the epoxide. More detailed studies with this system indicate the following: (1) the high-yield conversion of toluenes to benzyl chlorides proceeds with a deuterium isotope effect of 3. 6 and a rho ** plus value of minus 1. 7: (2) p-chloroanisole is the major product from anisole and is formed in a 22-fold greater quantity than o-chloroanisole; (3) the epoxidation of cis- and trans-alkenes is stereoselective but not completely stereospecific; (4) the chlorination of saturated hydrocarbons occurs with a selectivity that is experimentally identical with that of chlorine monoxide.
- Fonouni,Krishnan,Kuhn,Hamilton
-
p. 7672 - 7676
(2007/10/02)
-
- A PHOTOCHEMICAL SYNTHESIS OF βγ-EPOXYCYCLOHEXANONES
-
The βγ-epoxycyclohexanones (1), (9) and (10) have been prepared by photolysis of the pyruvate esters derived from the corresponding epoxyalcohols.
- Carless, Howard A. J.,Fekarurhobo, G. K.
-
p. 107 - 110
(2007/10/02)
-