- Rearrangements of α-Diazo-β-hydroxyketones for the Synthesis of Bicyclo[m.n.1]alkanones
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Rhodium-catalyzed decomposition of fused bicyclic α-diazo-β-hydroxyketones results in good yields of bridged bicyclo[m.n.1]ketones via a rearrangement pathway.
- Li, Zhengning,Lam, Shuk Mei,Ip, Ignatius,Wong, Wing-Tak,Chiu, Pauline
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supporting information
p. 4464 - 4467
(2017/09/11)
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- Silver-Catalyzed 7-exo-dig Cyclization of Silylenolether-ynesulfonamides
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Cyclization of silylenolether-ynesulfonamides proceeds at ambient temperature under mild reaction conditions under silver catalysis. Bridged compounds were obtained exclusively through 7-exo-dig reactions. The protocol is applicable to a wide range of substrates, thus leading to azabicyclic frameworks. Dig this! Cyclization of silylenolether-ynesulfonamides proceeds at ambient temperature under mild reaction conditions under silver catalysis. Bridged compounds were obtained exclusively through 7-exo-dig reactions. The protocol is applicable to a wide range of substrates, thus leading to azabicyclic frameworks.
- Heinrich, Clément F.,Fabre, Indira,Miesch, Laurence
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supporting information
p. 5170 - 5174
(2016/04/26)
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- Construction of Stereogenic α,α-Disubstituted Cycloalkanones via 1° Amine Thiourea Dual Catalysis: Experimental Scope and Computational Analyses
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The mechanistic exploration and an expanded experimental discussion of the organocatalyzed, asymmetric Pfau-dAngelo reaction by exploiting a bifunctional 1° amine thiourea catalyst system is disclosed. Notable breadth in substrate scope has been demonstrated on both the cyclic ketone moiety and the α,β-unsaturated electrophile. Exploration into the matched and mismatched selectivity of this process with a ketone containing pre-existing stereocenters has been demonstrated. Computational analyses of the reaction mechanism are reported. In concert with kinetic isotope effect (KIE) experiments, these computational results provide a detailed understanding of the likely mechanism, including the aspects of the organocatalyst scaffold that are critical for stereoselectivity.
- Kang, Jun Yong,Johnston, Ryne C.,Snyder, Kevin M.,Cheong, Paul Ha-Yeon,Carter, Rich G.
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p. 3629 - 3637
(2016/05/24)
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- Enantioselective Synthesis of Quaternary Carbon Stereogenic Centers through the Primary Amine-Catalyzed Michael Addition Reaction of α-Substituted Cyclic Ketones at High Pressure
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The enantioselective Michael addition reaction of α-substituted cyclic ketones with acrylates was efficiently promoted by a primary amine chiral catalyst under high-pressure conditions (1.0 GPa) in tetrahydrofuran. This method was highly successful for the construction of an all-carbon-substituted quaternary-carbon stereogenic center at the α-position of cyclic ketones in high enantiomeric excess, and could be conveniently applied to the formal synthesis of (+)-aspidospermidine. The Michael addition reaction of α-substituted cyclic ketones was efficiently promoted by a primary amine-based organocatalyst under high-pressure conditions (1.0 GPa) in tetrahydrofuran.
- Horinouchi, Ryo,Kamei, Kouhei,Watanabe, Riki,Hieda, Nobushige,Tatsumi, Naoki,Nakano, Keiji,Ichikawa, Yoshiyasu,Kotsuki, Hiyoshizo
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p. 4457 - 4463
(2015/07/27)
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- Palladium-Catalyzed Decarbonylative Dehydration for the Synthesis of α-Vinyl Carbonyl Compounds and Total Synthesis of (-)-Aspewentins A, B, and C
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The direct α-vinylation of carbonyl compounds to form a quaternary stereocenter is a challenging transformation. It was discovered that δ-oxocarboxylic acids can serve as masked vinyl compounds and be unveiled by palladium-catalyzed decarbonylative dehydr
- Liu, Yiyang,Virgil, Scott C.,Grubbs, Robert H.,Stoltz, Brian M.
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supporting information
p. 11800 - 11803
(2015/10/05)
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- Intramolecular reductive ketone-alkynoate coupling reaction promoted by (η2-propene)titanium
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Intramolecular reductive coupling of cycloalkanones tethered to alkynoates in the presence of (η2-propene)titanium was successfully performed to provide hydroxy-esters in a diastereoselective manner. Subsequent lactonization afforded angularly
- Schaefer, Christian,Miesch, Michel,Miesch, Laurence
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p. 3253 - 3257
(2012/06/01)
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- Primary amine, thiourea-based dual catalysis motif for synthesis of stereogenic, all-carbon quaternary center-containing cycloalkanones
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The enantioselective synthesis of α,α-disubstituted cycloalkanones has been developed using a primary amine, thiourea-based dual catalysis pathway. A range of electrophiles and ring sizes are tolerated under the reaction conditions. A possible catalytic c
- Kang, Jun Yong,Carter, Rich G.
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supporting information; experimental part
p. 3178 - 3181
(2012/08/07)
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- Room-temperature, acid-catalyzed [2+2] cycloadditions: Suppression of side reactions by using a flow microreactor system
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Added value: The [2+2] cycloaddition of silyl enol ethers with α,β-unsaturated esters, catalyzed by the superstrong acid triflic imide (Tf2NH), at room temperature in a flow microreactor system is reported. The micororeactor method achieves the [2+2] cycloaddition of unstable silyl enol ethers and acrylates, which is unsuccessful in batch reactors, even at room temperature. Copyright
- Kurahashi, Kei,Takemoto, Yoshiji,Takasu, Kiyosei
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experimental part
p. 270 - 273
(2012/05/05)
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- Regioselective photochemical rearrangement of N-mesyloxylactams
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N-Mesyloxylactams can undergo ring contraction either by C-3 (usually observed) or C-5 migration. C-5 migration can occur when the C-3 migration product possesses ring strain, but it does not usually compete with C-3 migration. The greater preference for C-3 migration is due to the carbonyl oxygen atom, which greatly stabilizes the intermediate. Studies of the photochemical rearrangement of N-mesyloxylactams showed that the lone pair of the carbonyl oxygen atom, and not the degree of the substitution atthe migrating carbon atoms, is the governing factor in the regioselectivity of the reaction. Copyright
- Pichette, Simon,Aubert-Nicol, Samuel,Lessard, Jean,Spino, Claude
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p. 1328 - 1335
(2012/04/05)
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- Formal (3+3) cycloaddition of silyl enol ethers catalyzed by trifric imide: Domino michael addition-claisen condensation accompanied with isomerization of silyl enol ethers
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We describe here a Tf2NH-catalyzed formal (3+3) cycloaddition of silyl enol ethers with acrylates as a new domino reaction. In the domino sequence, the catalyst activates Michael addition, deprotonation of the resulting silyloxonium cation and
- Azuma, Takumi,Takemoto, Yoshiji,Takasu, Kiyosei
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scheme or table
p. 1190 - 1193
(2011/10/09)
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- Photochemical rearrangement of N-mesyloxylactams: Stereospecific formation of N-heterocycles
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N-Mesyloxylactams undergo an efficient ring-contraction to N-heterocycles of various ring sizes. Yields increase with the degree of substitution α to the carbonyl. The stereochemical information of a chiral migrating carbon is conserved making this reacti
- Drouin, Alexandre,Winter, Dana K.,Pichette, Simon,Aubert-Nicol, Samuel,Lessard, Jean,Spino, Claude
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p. 164 - 169
(2011/03/19)
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- Asymmetric synthesis of polyfunctionalized allenic esters: Toward the synthesis of an iphionane sesquiterpene
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Tetrabutylammonium fluoride (TBAF) reacts smoothly with optically active acetylenic ω-keto esters to afford optically active allenic esters (ee >95%) in high yield. After protection of the hydroxyl group, the addition of morpholine followed by an acidic h
- Klein, Aurelie,Miesch, Michel
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p. 2613 - 2617
(2008/03/11)
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- Enantioselective Formal Total Synthesis of (-)-Dysidiolide
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(matrix presentd) An enantioselective formal total synthesis of the sesterterpene (-)-dysidiolide 1 beginning with an intermolecular Diels-Alder reaction of the allene ester 3 and the silyloxydiene 10 is reported.
- Jung, Michael E.,Nishimura, Nobuko
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p. 2113 - 2115
(2007/10/03)
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- A short asymmetric synthesis of 4,4-disubstituted-γ-butyrolactones from racemic 2-methylcyclohexanone in multigram scale
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A short and efficient asymmetric synthesis of both enantiomers (R)-1a-c and (S)-1a-c has been performed on a large scale and with high stereoselectivities from 2-methylcyclohexanone.
- Pinheiro, Sergio,De Farias, Florence M. C.,Saraiva, Analucia S.,Campos, Marcos P. A.
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p. 2031 - 2034
(2007/10/03)
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- Stereochemical aspects in the asymmetric Michael addition of chiral imines to substituted electrophilic alkenes
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The Michael-type addition of chiral imines, derived from racemic α-substituted cyclanones and optically active 1-phenylethylamine, to electrophilic alkenes, in neutral conditions, constitutes one of the most efficient methods for the stereocontrolled construction of quaternary carbon centers. In order to create an additional stereogenic center at the α- or β-position to the quaternary one, the behavior of a variety of α- and β-substituted alkenyl acceptors was examined. In general, these additions are highly regioselective, the alkylation taking place predominantly, if not exclusively, at the more substituted α-side of the imine function; however, in some cases (electrophilic alkenes 28 and 49), significant amounts (10-15%) of regioisomeric adducts were obtained. With the exception of methyl propiolate 52, a remarkable control of the absolute configuration of the adducts were always observed with these Michael acceptors. According to the general rule we have previously proposed, the alkylation process takes place preferentially on the less hindered π-face of the more substituted secondary enamine, in tautomeric equilibrium with the starting imine. An excellent diastereocontrol was always obtained by using the present α- and β-substituted alkenes. These stereochemical outcomes can be interpreted by invoking that the reaction proceeds through a compact approach of the reactants, the hydrogen atom at the nitrogen center of the enamine being transferred to the α-vinylic carbon atom of the acceptor, concertedly with the creation of the C-C bond. In this respect the "endo-approach" 58, in which the electron-withdrawing group of the acceptor faced to the nitrogen atom of the enamine (case of acceptors 10, methyl methacrylate, 24, 28, 43, 47, and 49) largely prevails over the "exo-approach" 59 (case of acceptor 38). This predominant "endo-preference" can be reasonably interpreted in terms of a cooperative effect between steric and stereoelectronic factors.
- Cave, Christian,Desmaele, Didier,D'Angelo, Jean,Riche, Claude,Chiaroni, Angele
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p. 4361 - 4368
(2007/10/03)
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- Total synthesis and absolute configuration of riccardiphenols A and B, isolated from the Liverwort Riccardia crassa
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The title compounds were synthesized as optically active forms using chiral Michael addition of the imine, prepared from 2-methylcyclohexanone and (S)-(-)-phenylethylamine, to methyl propiolate. The etherification of the intermediate triol was accomplished by TsOH-catalyzed cyclization. The absolute configurations of the natural products, riccardiphenols A and B, were established as 1 and 2, respectively.
- Tori,Hamaguchi,Sagawa,Sono,Asakawa
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p. 5362 - 5370
(2007/10/03)
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- Synthesis of Tridensone, a Sesquiterpene Ketone Isolated from the Liverwort Bazzania tridens. Structure Revision and Absolute Configuration
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The title compound and its isomer have been synthesized as optically active forms.The spectral data of the natural compounds 1 were identical with those of our synthetic isomer 1a showing that its structure should be revised and its absolute configuration
- Tori, Motoo,Kosaka, Kazuhiro,Asakawa, Yoshinori
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p. 2039 - 2042
(2007/10/02)
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- The asymmetric Michael reaction involving chiral imines: Use of acrylonitrile as acceptor and subsequent functionalization of the adducts
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Condensation of chiral imines 1 and acrylonitrile led to adduct (R)-6 with an ee ≥ 95%. This adduct has then been converted into chiral synthons 9, 11, 12 and 17.
- Desmaele,Zouhiri,D'Angelo
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p. 1645 - 1648
(2007/10/02)
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- Electrophilic α-formylation of carbonyl compounds using norephedrine-derived 2-metohoxy oxazolidines. A novel asymmetric formation of quaternary stereocenters
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The BF3·Et2O promoted addition of enamines and silylenolethers, to the nor-ephedrine-derived orthoamides 1 or 5 has been studied. A judicious choice of the type of nucleophile and electrophile leads to useful selectivities. When a quaternary α-carbonyl stereocenter is created, the direct removal of the chiral auxiliary is possible and renders the overall process an efficient asymmetric carbonyl α-formylation.
- Palazzi, Camillo,Poli, Giovanni,Scolastico, Carlo,Villa, Roberto
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p. 4223 - 4226
(2007/10/02)
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- THE ASYMMETRIC MICHAEL ADDITION PROCESS INVOLVING CHIRAL IMINES : STEREOCHEMICAL DATA IN SUPPORT OF A CYCLIC-LIKE TRANSITION STATE
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Addition of imine 4 to Michael acceptors 5 and 8 are both highly selective processes.The observed stereocontrol of the newly created asymmetric centers in the resulting adducts strongly supports cyclic-like transition states.
- d' Angelo, Jean,Guingant, Andre,Riche, Claude,Chiaroni, Angele
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p. 2667 - 2670
(2007/10/02)
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- REGIOSELECTIVITY OF ENAMINE REACTIONS, PREFERENTIAL 2,2-DISUBSTITUTION OF 2-METHYLCYCLOHEXANONE IMINES
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Secondary enamines, derived from imines of unsymmetrical α-substituted ketones, react with electrophilic alkenes at the more substituted position to give α,α-disubstituted ketones on hydrolysis.
- Hickmott, Peter W.,Rae, Bruce
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p. 2577 - 2580
(2007/10/02)
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- Carbazole acetic acid derivatives
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Tetrahydrocyclopent[b]indole-3-acetic acid, tetrahydrocarbazole-1-acetic acid and hexahydrocyclohept[b]-indole-6-acetic acid derivatives in which the carbon bearing alkyl, lower alkenyl or lower cycloalkyl are disclosed. The compounds are useful antiinflammatory agents and methods for their preparation and use are described.
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