- Highly efficient continuous flow reactions using singlet oxygen as a "Green" reagent
-
Described is a new method for the efficient in situ production of singlet oxygen in a simple continuous flow photochemical reactor. The extremely large interfacial area generated by running the biphasic mixture in a narrow channel at a high flow rate ensures high throughput as well as fast and efficient oxidation of various alkenes, 1,3-dienes, and thioethers on a preparative scale.
- Levesque, Francois,Seeberger, Peter H.
-
-
Read Online
- Ruthenium-lewis acid catalyzed asymmetric diels-alder reactions between dienes and α,β-unsaturated ketones
-
The complex [Ru(Cp)(R,R-BIPHOP-F)(acetone)][SbF6],(R,R)-1a. was used as catalyst for asymmetric Diels-Alder reactions between dienes (cyclopentadiene, methylcyclopentadienc, isoprene, 2,3-dimethylbutadiene) and α,β-unsaturated ketones (methyl vinyl ketone (MVK). ethyl vinyl ketone, divinyl ketone, α-bromovinyl methyl ketone and α-chlorovinyl methyl ketone). The cycloaddition products were obtained in yields of 50-_90% and with enantioselectivities up to 96% ee. Ethyl vinyl ketone, divinyl ketone and the halogenated vinyl ketones worked best and their reactions with acyclic dienes consistently provided products with >90% ee. α-Chlorovinyl methyl ketone performed better than α-bromovinyl methyl ketone. The reaction also provided a [4.3.1]bicyclic ring system in 95% ee through an intramolecular cycloaddition reaction. Crystal structure determinations of [Ru(Cp)((S,S)-BIPHOP-F)(mvk)]-[SbF6], (S,S)-1b, and [Ru(Cp)((R,R)-Me4BIPHOP-F)(acrolein)][SbF6], (R,R)-2b, provided the basis for a rationalization of the asymmetric induction.
- Rickerby, Jenny,Vallet, Martial,Bernardinelli, Gerald,Viton, Florian,Kuendig, E. Peter
-
-
Read Online
- Highly Diastereoselective Synthesis of Substituted Epichlorohydrins and Regioselective Preparation of Allyl Alcohols using Chloro or Idomethyllithium
-
Substituted epichlorohydrins 3 or 6 are obtained α-bromo or α-chlorocarbonyl compounds (1 or 4) and chloro or iodomethyllithium, respectively.Starting from α-bromocarbonyl compounds 1 or acyclic α-chloro ketones the reaction takes place with total diastereoselectivity.Treatment of epichlorohydrins 3 or 6 with lithium iodide affords the same substituted allyl alcohols 7 in a regioselective manner.A mechanism to explain this transformation is proposed.Regioisomeric allyl alcohols 11 are prepared by reaction of epichlorohydrins 6 with lithium powder.
- Concellon, Jose M.,Llavona, Lujan,Bernad, Pablo L. Jr.
-
-
Read Online
- Preparation of disubstituted epichlorohydrins with total diastereoselectivity. Transformation of α-bromocarbonyl compounds into allyl alcohols
-
Epichlorohydrins 3 have been obtained with total diastereoselectivity from α-bromocarbonyl compounds and chloromethyllithium generated in situ. The treatment of compounds 3 with lithium iodide or lithium powder affords allyl alcohols 4 in a regioselective manner.
- Barluenga, Jose,Llavona, Lujan,Bernad, Pablo L.,Concellon, Jose M.
-
-
Read Online
- Novel conversion of 1,2-disubstituted cis-epoxides to one-carbon homologated allylic alcohols using dimethylsulfonium methylide
-
matrix presented The treatment of cis-epoxides with an excess of dimethylsulfonium methylide affords one-carbon homologated allylic alcohols in good to excellent yields.
- Alcaraz, Lilian,Cridland, Andrew,Kinchin, Elizabeth
-
-
Read Online
- SYNTHESIS OF 2-SUBSTITUTED 1,3-BUTADIENYL COMPOUNDS BY PALLADIUM-CATALYZED REGIOSELECTIVE 1,2-ELIMINATION REACTION OF METHYLVINYLCARBINOL ACETATES
-
Alkylation of the dianion of 3-methyl-3-buten-2-ol, followed by acetylation and palladium-catalyzed 1,2-elimination reaction of the so obtained methylvinylcarbinol acetates allows to synthesize regioselectively 2-substituted 1,3-butadienyl compounds having high isomeric purity.
- Carpita, Adriano,Bonaccorsi, Fabrizio,Rossi, Renzo
-
-
Read Online
- TRICYCLIC HETEROCYCLE COMPOUNDS USEFUL AS HIV INTEGRASE INHIBITORS
-
The present invention relates to Tricyclic Heterocycle Compounds of Formula (I): (I) and pharmaceutically acceptable salts or prodrug thereof, wherein R1, R2, R3, R4, R5, R6 and n are as defined herein. The present invention also relates to compositions comprising at least one Tricyclic Heterocycle Compound, and methods of using the Tricyclic Heterocycle Compounds for treating or preventing HIV infection in a subject.
- -
-
Page/Page column 75
(2019/11/12)
-
- Self-assembled benzophenone bis-urea macrocycles facilitate selective oxidations by singlet oxygen
-
This manuscript investigates how incorporation of benzophenone, a well-known triplet sensitizer, within a bis-urea macrocycle, which self-assembles into a columnar host, influences its photophysical properties and affects the reactivity of bound guest molecules. We further report the generation of a remarkably stable organic radical. As expected, UV irradiation of the host suspended in oxygenated solvents efficiently generates singlet oxygen similar to the parent benzophenone. In addition, this host can bind guests such as 2-methyl-2-butene and cumene to form stable solid host-guest complexes. Subsequent UV irradiation of these complexes facilitated the selective oxidation of 2-methyl-2-butene into the allylic alcohol, 3-methyl-2-buten-1-ol, at 90% selectivity as well as the selective reaction of cumene to the tertiary alcohol, α,α′-dimethyl benzyl alcohol, at 63% selectivity. However, these products usually arise through radical pathways and are not observed in the presence of benzophenone in solution. In contrast, typical reactions with benzophenone result in the formation of the reactive singlet oxygen that reacts with alkenes to form endoperoxides, diooxetanes, or hydroperoxides, which are not observed in our system. Our results suggest that the confinement, the formation of a stable radical species, and the singlet oxygen photoproduction are responsible for the selective oxidation processes. A greater understanding of the mechanism of this selective oxidation could lead to development of greener oxidants.
- Geer, Michael F.,Walla, Michael D.,Solntsev, Kyril M.,Strassert, Cristian A.,Shimizu, Linda S.
-
p. 5568 - 5578
(2013/07/26)
-
- Ionic liquids for enhancing the enantioselectivity of isolated BVMO-catalysed oxidations
-
The present study describes the first-time usage of an isolated thermostable Baeyer-Villiger monooxygenase (phenylacetone monooxygenase, PAMO) in the presence of ionic liquids. The stability, activity and selectivity of PAMO as an oxidative enzyme in the presence of different ionic liquids were studied. This revealed that the addition of some specific ionic liquids, such Ammoeng 102 and [bmim]MeSO4, can significantly enhance the E-value in the oxidation of racemic benzylketones. Moreover, the use of ionic liquids increases the optimal substrate concentration for performing Baeyer-Villiger oxidation, thereby extending the biocatalytic repertoire of PAMO for synthetic applications.
- Rodriguez, Cristina,De Gonzalo, Gonzalo,Fraaije, Marco W.,Gotor, Vicente
-
experimental part
p. 2255 - 2260
(2011/02/24)
-
- Baeyer-Villiger monooxygenase-catalyzed kinetic resolution of racemic α-alkyl benzyl ketones: enzymatic synthesis of α-alkyl benzylketones and α-alkyl benzylesters
-
The application of three BVMOs for the enantioselective oxidation of 3-phenylbutan-2-ones with different substituents in the aromatic moiety is described. By choosing the appropriate biocatalyst and substrate combination, chiral ketones and esters can be obtained with excellent enantiopurities. This methodology could also be applied to the resolution of racemic α-alkyl benzylketones with longer alkyl chains as well as with two substituted α-substituted benzylacetones. A kinetic analysis revealed that the BVMOs studied effectively convert all tested compounds showing that the enzymes are tolerant towards the substrate structure while being highly enantioselective. These properties render BVMOs as valuable biocatalysts for the preparation of compounds with high interest in organic synthesis.
- Rodriguez, Cristina,Gonzalo, Gonzalo de,Torres Pazmino, Daniel E.,Fraaije, Marco W.,Gotor, Vicente
-
experimental part
p. 1168 - 1173
(2009/10/02)
-
- Confined space-controlled hydroperoxidation of trisubstituted alkenes adsorbed on pentasil zeolites
-
Photosensitized oxidation of trialkylalkenes 2-methyl-2-pentene (1), 1-methylcyclohexene (2), trans-3-methyl-2-pentene (3), cis-3-methyl-2-pentene (4), and 2-methyl-2-butene (5) included in the internal framework of Na-ZSM-5 zeolites was investigated. The zeolite samples having adsorbed the alkenes were suspended in isooctane, and the sensitizer, tetraphenylporphyrin (TPP), was dissolved in the solution. Singlet oxygen produced in the solution diffused into the internal framework of the zeolites and reacted with alkenes. For all the substrates studied, the ene-type allylic hydroperoxides were obtained in a highly regioselective manner. The regiochemistry for 1-4 in favor of the allylic hydrogen abstraction from the largest substituents is in contrast to their photooxidation within the dye-supported zeolite Na-Y, where the secondary hydroperoxides are preferentially produced. The tight confinement of the alkenes within the narrow channels of the ZSM-5 zeolites is likely to be responsible for this selectivity.
- Chen, Yu-Zhe,Wu, Li-Zhu,Zhang, Li-Ping,Tung, Chen-Ho
-
p. 4676 - 4681
(2007/10/03)
-
- Kinetics and mechanism of the liquid-phase rearrangement of 2-Methyl-2,3-epoxybutane in the presence of a magnesium bromide complex
-
The mechanism of intramolecular rearrangement of epoxides in the presence of the MgBr2 · 2H2O · 4DMF catalytic complex was proposed on the basis of a kinetic study of the liquid-phase isomerization of 2-methyl-2,3-epoxybutane and data on the influence of the ligand environment of the catalyst, solvent nature, and the epoxide structure. Copyright
- Mel'nik,Khvatova,Moskvichev,Srednev
-
p. 275 - 278
(2007/10/03)
-
- Highly diastereoselective hydrostannylation of allyl and homoallyl alcohols with dibutyl(trifluoromethanesulfoxy)stannane
-
Dibutyl(trifluoromethanesulfoxy)stannane (Bu2Sn(OTf)H, 1a) was found to be very valuable for highly diastereoselective homolytic hydrostannylation of allyl and homoallyl alcohols. α,β-Disubstituted allyl alcohols and α,γ-disubstituted homoallyl alcohols were converted into γ- and δ-stannylated alcohols with high 1,2-syn and 1,3-syn diastereoselectivity, respectively. The origin of the stereochemical outcomes can be rationalized by conformational fixation of the intermediary β-stannylalkyl radical by coordination of the hydroxy group to the Lewis acidic tin center. Copyright
- Miura, Katsukiyo,Wang, Di,Hosomi, Akira
-
p. 9366 - 9367
(2007/10/03)
-
- Liquid-phase isomerization of saturated and unsaturated epoxides
-
The liquid-phase isomerization of a variety of epoxides was studied using a complex catalyst system based on magnesium bromide and dimethylformamide. The data obtained elucidate the mechanism of the liquid-phase isomerization and show the range of oxygen-containing compounds which can be prepared through this reaction.
- Mel'nik,Khvatova,Moskvichev,Srednev,Egorova
-
p. 167 - 169
(2007/10/03)
-
- The effect of solvent on the liquid-phase catalytic isomerization reaction of 2-methyl-2,3-epoxybutane
-
The effect of solvent on the rate and direction of the liquid-phase isomerization reaction of 2-methyl-2,3-epoxybutane was studied. The solvent effect was found to be due to a change in the stability of the transition state and its influence on the conformational equilibrium. A possibility was shown for controlling the chemical process by varying the character of the reaction medium.
- Mel'nik,Khvatova,Moskvichev,Srednev,Egorova
-
p. 277 - 280
(2007/10/03)
-
- Total synthesis of korormicin
-
Recently, we have assigned the (5S,3′R,9′S,10′R) stereochemistry to planar korormicin (1) on the basis of the specific rotations of the four possible diastereoisomers [i.e., (5S,3′R,9′S,10′R), (5S,3′S,9′S,10′R), (5S,3′S,9′R,10′S), and (5S,3′R,9′R,10′S) isomers], which were prepared by a total synthesis. In this article, we describe the synthetic aspects in detail. The intermediates in the synthesis are enamino lactone (5S)-4 and both enantiomers of acid 5 and of boronate ester 7. Lactone (5S)-4 and boronate 7 with (9′S,10′R) and (9′R,10′S) chiralities were prepared through asymmetric dihydroxylation of olefins 11 and 30, respectively, with AD-mix-α or -β. Compounds (3′R)- and (3′S)-5 were prepared by kinetic resolution of rac-19 with asymmetric epoxidation. Condensation of (5S)-4 and (3′R)- or (3′S)-5 with DCC in the presence of DMAP and PPTS furnished the advanced intermediate 6 with (5S,3′R) and (5S,3′S) chiralities in good yields. Addition of PPTS was important to prevent formation of acyl urea 24. A nickel-catalyzed coupling reaction between 6 and 8 [prepared in situ from (9′S,10′R)- or (9′R, 10′S)-7 and MeLi] produced 9, which upon deprotection with Bu4NF furnished the four diastereoisomers of korormicin (1).
- Kobayashi, Yuichi,Yoshida, Shinya,Nakayama, Yuji
-
p. 1873 - 1881
(2007/10/03)
-
- Stereoselective intramolecular acylation of y'-benzoyloxyphosphine oxides with an internal chlorotrimethylsilane trap: Isolation of silylated tetrahedral intermediates
-
The kinetic products of the intramolecular acylation of y'-benzoyloxyphosphine oxides were revealed by conducting the reaction in the presence of an internal trapping agent. A high level of stereocontrol over the formation of both ' : ' the stereogenic centre a to phosphorus and the hemiacetal centre was observed. The stereochemistry of the products was determined by X-ray crystallography and 'H NMR and the stereoselectivity of the reaction is explained in terms of the known structure and configurational instability of lithiated phosphine oxides. The Royal Society of Chemistry 1999.
- Feeder, Neu,Hutton, Gordon,Nelson, Adam,Warren, Stuart
-
p. 3413 - 3424
(2007/10/03)
-
- Isomerization of 2-methyl-2,3-epoxybutane in the presence of homogeneous catalysts
-
Data on isomerization of 2-methyl-2,3-epoxybutane in liquid phase in the presence of magnesium bromide as a homogeneous catalyst are presented. 3-Methyl-2-bytanone, 2-methyl-1-buten-3-ol, and 2-methyl-2,3-butanediol are formed in the reaction with the yields of 64.8, 27.6, and 7.6%, respectively. Copyright
- Shemanaeva,Mel'nik,Razina,Egorova,Kryukov
-
p. 191 - 195
(2007/10/03)
-
- Deamination Reactions, 44. Decomposition of 1-Alkylcyclopropanediazonium Ions
-
1-Methyl- (17), 1,2-dimethyl- (41, 44), 1-propyl- (64), 1-(1-methylethyl)cyclopropanediazonium ions (80), and -1-diazonium ions (93) have been generated by alkaline cleavage of the analogous nitrosocarbamates in methanol.Cyclopropyl-allyl transformation and nucleophilic displacement were the only reactions of 17, 41, 44, and 93 while elimination and 1,2-shifts of an α-hydrogen compete increasingly with 64 and 80.The stereochemistry of ring cleavage and nucleophilic displacement has been explored, using 2-D labels in the case of 17 and 93.Cyclopropanediazonium ions (1) and 41 react stereospecifically, 17 and 44 are moderately stereoselective (ca. 85:15), and 93 is entirely unselective.The data indicate a gradual changeover from concerted to stepwise mechanisms.Appreciable stabilization of the positive charge is required to reach the SN1 extreme.
- Kirmse, Wolfgang,Rode, Jutta,Rode, Klaus
-
p. 3672 - 3693
(2007/10/02)
-
- Convenient deuterium labeling on a gas-liquid chromatography column. Preparative scale formation of α,β-unsaturated Od-alcohols
-
Several α,β-unsaturated ethylenic and acetylenic alcohols 1-11 were conveniently deuterated on oxygen, by a GLC technique, with high yields and 80 to 98percent deuterium incorporation.
- Georgoulis, Constantin,Smadja, William,Ville, Guy
-
p. 269 - 270
(2007/10/02)
-
- Synthesis of (R)- and (S)-Acetoin (3-Hydroxybutan-2-one)
-
Two synthetic routes to the enantiomers of acetoin (2) of high optical purity have been devised.One starting from (S)-3-methylbut-3-en-2-ol (9) led to (S)-(+)-acetoin (13).The other, starting from (2R,3R)-butane-2,3-diol gave (R)-(-)-acetoin (16).
- Crout, David H.G.,Morrey, Stephen M.
-
p. 2435 - 2440
(2007/10/02)
-
- Acid-catalysed isomerisation of epoxides to allylic alcohols
-
The acid-catalysed isomerisation of epoxides containing tertiary ring carbon atoms results in the selective formation of the corresponding allylic alcohols if the reaction is carried out in methylene chloride or chloroform in the presence of small quantities of sulfuric acid (10 mmol/l) or methanesulfonic acid (100 mmol/l).The zero-order kinetics of the isomerisation have been rationalised by a mechanism in which a rapidly and quantitatively formed epoxide-acid intermediate slowly decomposes into allylic alcohol and acid.
- Zon, A. van,Huis, R.
-
p. 425 - 429
(2007/10/02)
-
- Synthesis of isoprenoid 1,5-dienes
-
Aliphatic acids containing an isoprenoid 1,5-diene moiety are prepared in high yields by the selective gamma alkylation of α,β-unsaturated acids with allylic electrophiles. The gamma-regioselectivity of the alkylation is controlled by the use of the dicopper(I) dienolates prepared from the α,β-unsaturated acids. The method offers a particularly facile means for synthesizing isoprenoid 1,5-diene natural products such as farnesoic acid by alkylation of senecioic acid with geranyl bromide; geranoic acid by alkylation of senecioic acid with 3,3-dimethallyl bromide; and dl-lanceol by alkylation of tiglic acid with an allylic bromide derived from dl-limonene. Such products find use in the synthesis of insect pheremones, insect juvenile hormones, and components of perfumes.
- -
-
-