2890-62-2Relevant articles and documents
Synthesis of Vicinal Quaternary All-Carbon Centers via Acid-catalyzed Cycloisomerization of Neopentylic Epoxides
Schmid, Matthias,Sokol, Kevin R.,Wein, Lukas A.,Torres Venegas, Sofia,Meisenbichler, Christina,Wurst, Klaus,Podewitz, Maren,Magauer, Thomas
supporting information, p. 6526 - 6531 (2020/09/02)
We report our studies on the development of a catalytic cycloisomerization of 2,2-disubstituted neopentylic epoxides to produce highly substituted tetralins and chromanes. Termination of the sequence occurs via Friedel-Crafts-type alkylation of the remote (hetero)arene linker. The transformation is efficiently promoted by sulfuric acid and proceeds best in 1,1,1,3,3,3-hexafluoroisopropanol (HFIP) as the solvent. Variation of the substitution pattern provided detailed insights into the migration tendencies and revealed a competing disproportionation pathway of dihydronaphthalenes.
Photocatalytic degradation of water taste and odour compounds in the presence of polyoxometalates and TiO2: Intermediates and degradation pathways
Fotiou, Theodora,Triantis, Theodoros M.,Kaloudis, Triantafyllos,Papaconstantinou, Elias,Hiskia, Anastasia
, p. 1 - 9 (2014/05/20)
Geosmin (GSM) and 2-methylisoborneol (MIB) are produced by several species of cyanobacteria and actinomycetes. These compounds can taint water and fish causing undesirable taste and odours. Studies have shown that GSM/MIB are resistant in standard water treatments. Polyoxometalates (POM) are efficient photocatalysts in the degradation and mineralization of a great variety of organic pollutants, presenting similar behaviour with the widely published titanium dioxide (TiO2). Photocatalytic degradation of GSM and MIB under UV-A light in the presence of a characteristic POM photocatalyst, SiW 12O404-, in aqueous solution has been studied and compared with the photodegradation by TiO2 suspensions. GSM and MIB are effectively degraded in the presence of both photocatalysts. Addition of OH radical scavengers (KBr and tertiary butyl alcohol, TBA) retards the photodegradation rates of both compounds, suggesting that photodegradation mechanism takes place via OH radicals. Intermediates identified using GC-MS in the case of GSM and MIB, are mainly identical in the presence of both photocatalysts, also suggesting a common reaction mechanism. Possible photocatalytic degradation pathway for both GSM and MIB is proposed.
Enantioselective borohydride reduction of aliphatic ketones catalyzed by ketoiminatocobalt(iii) complex with 1-chlorovinyl axial ligand
Tsubo, Tatsuyuki,Chen, Hsiu-Hui,Yokomori, Minako,Fukui, Kosuke,Kikuchi, Satoshi,Yamada, Tohru
supporting information; experimental part, p. 780 - 782 (2012/09/22)
For the enantioselective borohydride reduction of aliphatic ketones, the optically active ketoiminatocobalt(II) catalysts was successfully designed based on their axial ligand. Instead of chloroform for the aryl ketone reduction, various axial ligand precursors were examined for the aliphatic ketone. Consequently, 1, 1, 1-trichloroethane was found to be the most effective activator of the cobalt(II) complexes to generate the corresponding 1-chlorovinyl cobalt(III) derivatives as the reactive intermediate. Several aliphatic ketones were successfully reduced to afford the corresponding secondary alcohols with high enantioselectivities.
Six- and eightfold palladium-catalyzed gross-coupling reactions of hexa- and octabromoarenes
Stulgies, Balder,Prinz, Peter,Magull, Joerg,Rauch, Karsten,Meindl, Kathrin,Ruehl, Stephan,De Meijere, Armin
, p. 308 - 320 (2007/10/03)
Palladium-catalyzed sixfold coupling of hexabromobenzene (20) with a variety of alkenylboronates and alkenylstannanes provided hexaalkenylbenzenes 1 in up to 73% and 16 to 41% yields, respectively. In some cases pentaalkenylbenzenes 21 were isolated as the main products (up to 75%). Some functionally substituted hexaalkenylbenzene derivatives containing oxygen or sulfur atoms in each of their six arms have also been prepared (16 to 24% yield). The sixfold coupling of the less sterically encumbered 2, 3, 6, 7, 10, 11-hexabromotriphenylene (24) gave the desired hexakis(3,3-dimethyl-1-butenyl) triphenylene (25) in 93% yield. The first successful cross-coupling reaction of octabromonaphthalene (26) gave octakis-(3,3-dimethyl-1-butenyl)naphthalene (27) in 21% yield. Crystal structure analyses disclose that, depending on the nature of the substituents, the six arms are positioned either all on the same side of the central benzene ring as in 1a and 1i, making them nicely cup-shaped molecules, or alternatingly above and below the central plane las in 1h and 23. In 27, the four arms at C-1, 4, 6, 7 are down, while the others are up, or vice versa. Upon catalytic hydrogenation, 1a yielded 89% of hexakis(tert-butylethyl)benzene (23). Some efficient accesses to alkynes with sterically demanding substituents are also described. Elimination of phosphoric acid from the enol phosphate derived from the corresponding methyl ketones gave 1-ethynyladamantane (3b, 62% yield), 1-ethynyl-1-methylcyclohexane (3c, 85%) and 3,3-dimethylpentyne (3e, 65%). 1-(Trimethylsilyl)ethynylcyclopropane (7) was used to prepare 1-ethynyl-1-methylcyclopropane (3d) (two steps, 64% overall yield). The functionally substituted alkynes 3 f-h were synthesized in multistep sequences starting from the propargyl chloride 11, which was prepared in high yields from the dimethylpropargyl alcohol 10 (94%). The alkenylstannanes 19 were prepared by hydrostannation of the corresponding alkynes in moderate to high yields (42-97%), and the alkenylboronates 2 and 4 by hydroboration with catecholborane (27-96% yield) or pinacolborane (26-69% yield).
THERAPEUTIC AGENT FOR DIABETES
-
, (2008/06/13)
A therapeutic agent for diabetes, which comprises a compound of the formula [I] wherein Xis a group of the formula wherein R4and R5are the same or different and each is a hydrogen atom, an optionally substituted alkyl having 1 to 5 carbon atoms and the like, and R6is a hydrogen atom or an amino-protecting group; R1is an optionally substituted alkyl having 1 to 5 carbon atoms, an optionally substituted alkenyl having 2 to 6 carbon atoms and the like, R2is a hydrogen atom, an optionally substituted alkyl having 1 to 5 carbon atoms and the like, R2' is a hydrogen atom, and R3is an optionally substituted alkyl having 1 to 5 carbon atoms and the like, a prodrug thereof, a pharmaceutically acceptable salt thereof, a hydrate thereof and a solvate thereof. The compound of the present invention shows superior blood sugar decreasing action on the state of hyperglycemia, but does not affect the blood sugar when it is in the normal range or in the hypoglycemic state, which means that it is free of serious side effects such as hypoglycemia. Therefore, the compound of the present invention is useful as a therapeutic drug for diabetes and also useful as a preventive of the chronic complications of diabetes.
On the mechanism of the intramolecular samarium barbier reaction. Probes for formation of radical and organosamarium intermediates
Curran, Dennis P.,Gu, Xin,Zhang, Wei,Dowd, Paul
, p. 9023 - 9042 (2007/10/03)
A new type of mechanistic probe for the intramolecular samarium Barbier reaction has been designed, and two different probe substrates have been investigated in detail. Remarkably, no unambiguous evidence could be obtained in favor of any of the obvious intermediates (free alkyl or alkoxy radicals, ketyls, organosamarium species) that are postulated for this reaction. Several possibilities for modified mechanisms are suggested.
Clemmensen Reduction. XI. Fragmentation Reactions of Some 3-Acetylcycloalkanones
Bailey, Karen E.,Davis, Brian R.
, p. 1827 - 1834 (2007/10/03)
Clemmensen reduction of a series of 3-acetylcycloalkanones yields, as the major product, an acyclic unsaturated ketone, the product of fragmentation.Some normal carbonyl-methylene reduction also occurs.A mechanistic rationale for the fragmentation is advanced.
REACTION OF CHLOROSULFONYL ISOCYANATE WITH 1,2-DIOLS: REARRANGEMENT AND FORMATION OF CARBONATES
Joseph, Sajan P.,Dhar, D. N.
, p. 2295 - 2302 (2007/10/02)
1,2-Diols, 1a-e, upon reaction with chlorosulfonyl isocyanate (CSI) gave the ketones, 3a-e.Under similar experimental conditions, 1,2-diols, 1f-k, gave carbonyl compounds, 3f-k, carbonates, 6f-k, carboxamides, 7h,i, and the epoxide, 5i.
Wanderungstendenzen cyclischer, polycyclischer und methylverzweigter Alkylreste bei der Beckmann-Umlagerung
Langhals, Heinz,Ruechardt, Christoph
, p. 3831 - 3854 (2007/10/02)
The migration aptitudes of polycyclic bridgehead groups, cycloalkyl groups as well as of β-, γ- and δ-branched alkyl groups in the Chapman variant of the Beckmann rearrangement were determined.From these data it is concluded that at transition state 2 the migrating group is not resembling a planarised carbenium ion R+, but rather a pentacoordinated carbonium ion structure.Because only small geometrical changes occur in the migrating group vertical stabilisation of charge at transition state is believed to have significant influence on the migration aptitudes.
Malonate Anion Induced Favorskii Type Rearrangement. 21. Reaction of Acyclic α-Halo Ketones with Carbanions Leading to Cyclopropanols2
Sakai, Takashi,Katayama, Tsuyoshi,Takeda, Akira
, p. 2924 - 2931 (2007/10/02)
The reaction of 3-bromo-3-methyl-2-butanone (6a) with ethyl sodiomalonate (2) in refluxing THF gave 1--2,2-dimethylcyclopropanol (9a), the Favorskii-type intermediate, in 51percent yield.Similar reactions of acyclic halo ketones such as 2-bromo-2-methyl-3-pentanone (6b), 1-acetyl-1-bromocyclohexane (6c), and 1-acetyl-1-bromocyclopentane (6d) with 2 also gave the corresponding cyclopropanols 9b-d in 42-56percent yields.On the contrary, the α-halo ketones (6f-l) possessing a primary or secondary carbon atom at the α position afforded the SN2 products10f-l.The behavior of 3-chloro-3-methyl-2-butanone (6e) was quite different from that of its bromo homologue 6a, giving a mixture (16:45:39) of 9a, 1,1-bis-2,2-dimethylcyclopropane (14), and 1--2,2-dimethyl-1-cyclopropane (15) in 75percent total yield.Hydrolysis of 9a with 0.2 N NaOH at room temperature gave the acid ester 18, which afforded a mixture of 3-carboxy-4,5,5-trimethyl-2(5H)-furanone (22a, 27percent yield) and its ethyl ester (22b, 39percent yield) on heating.When the hydrolysis was carried out in 2 N NaOH at 10 deg C, 9a gave 1-(dicarboxymethyl)-2,2-dimethylcyclopropanol (23, 60percent yield) together with 22a (27percent yield).Similar hydrolysis of 9a at 30 deg C afforded 4,4-dimethyl-3-oxopentanoic acid (24, 38percent yield) and 3,3-dimethyl-2-butanone (25, 18percent yield).The bromination of 9a with Br2 caused the ring opening to give ethyl 5-bromo-4,4-dimethyl-2-(ethoxycarbonyl)-3-oxopentanoate (30) in 76percent yield.The ester 30 was cyclized to the oxetane 31 in 77percent yield.
