42599-23-5Relevant articles and documents
Stereoselective Csp3?Csp2 Cross-Couplings of Chiral Secondary Alkylzinc Reagents with Alkenyl and Aryl Halides
Skotnitzki, Juri,Kremsmair, Alexander,Keefer, Daniel,Gong, Ye,de Vivie-Riedle, Regina,Knochel, Paul
supporting information, p. 320 - 324 (2019/11/26)
We report palladium-catalyzed cross-coupling reactions of chiral secondary non-stabilized dialkylzinc reagents, prepared from readily available chiral secondary alkyl iodides, with alkenyl and aryl halides. This method provides α-chiral alkenes and arenes with very high retention of configuration (dr up to 98:2) and satisfactory overall yields (up to 76 % for 3 reaction steps). The configurational stability of these chiral non-stabilized dialkylzinc reagents was determined and exceeded several hours at 25 °C. DFT calculations were performed to rationalize the stereoretention during the catalytic cycle. Furthermore, the cross-coupling reaction was applied in an efficient total synthesis of the sesquiterpenes (S)- and (R)-curcumene with control of the absolute stereochemistry.
Second-Generation Synthesis of the Northern Fragment of Mandelalide A: Role of π-Stacking on Sharpless Dihydroxylation of cis-Enynes
Ghosh, Ankan,Brueckner, Alexander C.,Cheong, Paul Ha-Yeon,Carter, Rich G.
, p. 9196 - 9214 (2019/08/12)
The development of a π-stacking-based approach for increased stereoselectivity in Sharpless asymmetric and diastereomeric dihydroxylation of cis-enynes is disclosed. The use of neighboring, electron-rich benzoate esters proved key to the success of this process. Density functional theory study suggests that the substrate benzoate ester group rigidifies the dihydroxylation transition states by forming a favorable π-stacking interaction in both Major-TS and Minor-TS. The energetic preference for the Major-TS was found in part because of the favorable eclipsing conformation of the alkene substituent as opposed to the disfavored bisecting conformation found in the Minor-TS. The application to a second-generation synthesis of the C15-C24 northern portion of mandelalide A is demonstrated.
A New Entry of Practical and Chemoselective Iodocarbenoids for Carbonyl Iodomethylenation
Yan, Tu-Hsin,Chen, Mei-Yuan
, p. 390 - 394 (2017/04/24)
Direct oxidative addition of CHI3 to the Mg-TiCl4 bimetallic species resulted in the generation of a highly chemoselective and practically convenient iodomethylenetitanium complex, which efficiently effected condensation even with enolizable or inert carbonyl compounds, such as sterically congested ketones, to provide vinyl iodide compounds.
Synthetic utility of tribenzyltin hydride and its derivatives as easily accessible, removable, and decomposable organotin reagents
Yamakawa, Takeshi,Kinoshita, Hidenori,Miura, Katsukiyo
supporting information, p. 129 - 134 (2013/03/13)
Radical reactions using tribenzyltin hydride (Bn3SnH) easily prepared from tin and benzyl chloride were studied. The Et3B- initiated reduction and cyclization of haloalkanes and haloalkenes with Bn 3SnH proceeded efficiently. Homolytic hydrostannylation of alkynes with Bn3SnH followed by treatment with electrophiles gave functionalized alkenes in good to high yields. The organotin byproducts formed could be easily removable by filtration and silica-gel column chromatography without any pretreatment. It was also found that tribenzyltin chloride (Bn 3SnCl) easily decomposed to benzyl alcohol in a basic solution of H2O2.
Catalytic enantioselective conjugate allylation of unsaturated methylidene ketones
Brozek, Laura A.,Sieber, Joshua D.,Morken, James P.
supporting information; scheme or table, p. 995 - 997 (2011/05/15)
The use of unsaturated methylidene ketones in catalytic conjugate allylations allows a significant expansion in substrate scope and, with appropriate chiral ligands, occurs in a highly enantioselective fashion.(Figure Presented)
A stereoselective palladium-mediated reductive coupling of electron-deficient terminal iodoalkenes
Batsanov, Andrei S.,Knowles, Jonathan P.,Samsam, Benedict,Whiting, Andrew
supporting information; experimental part, p. 227 - 233 (2009/04/11)
Iodoacrylate esters undergo palladium-catalysed reductive homocoupling to derive dienyl diester derivatives. This reductive coupling can be extended to ester-substituted terminal iododienes to derive tetraene diesters. In all cases, the reactions show relatively high levels of stereocontrol, which shows an inversion of stereochemistry about one iodoalkene unit. This process, and the suggestion that the reaction releases diiodine, is consistent with a syn-1,2-addition of an iodopalladium(II)-alkene species across another iodoalkene unit (carbometallation step), followed by reductive syn-elimination of iodopalladium iodide to derive palladium(II) iodide. It appears that under the reaction conditions employed, palladium(II) iodide may equilibrate to palladium(O) and diiodine, which can be observed or trapped out from the reaction mixture.
BICYCLIC AROMATIC COMPOUNDS USEFUL AS INHIBITORS OF MITOGEN-ACTIVATED PROTEIN KINASE-ACTIVATED PROTEIN KINASE-2
-
Page/Page column 49-50, (2008/06/13)
A compound of formula (I) or a pharmaceutically acceptable salt or prodrug ester thereof: wherein the groups R1-R6, A and Y are as defined in the specification, as inhibitors of (MK2 or MAPKAP kinase-2).
Design, synthesis and biological evaluation of novel, simplified analogues of laulimalide: Modification of the side chain
Paterson, Ian,Menche, Dirk,Hakansson, Anders E.,Longstaff, Adrian,Wong, David,Barasoain, Isabel,Buey, Ruben M.,Diaz, J. Fernando
, p. 2243 - 2247 (2007/10/03)
Novel, simplified analogues of the microtubule-stabilizing anticancer agent laulimalide, including the first derivatives with unnatural side chains, were designed by molecular modelling, synthesized by a late-stage diversification strategy, and evaluated in vitro for growth inhibition of human ovarian carcinoma cell lines (A2780, A2780/AD10).
An Alternative Procedure in the Takai Reaction Using Chromium(III) Chloride Hexahydrate as a Convenient Source of Chromium(II)
Auge, Jacques,Boucard, Valerie,Gil, Richard,Lubin-Germain, Nadege,Picard, Julien,Uziel, Jacques
, p. 3733 - 3739 (2007/10/03)
An alternative procedure in the Takai reaction using chromium(III) chloride hexahydrate as the source of Cr(II) was performed. The use of zinc as Cr(III) reducer allowed us to carry out the iodovinylation of aldehydes in 63-99% yields. With the Garner and Dondoni aldehydes, these conditions along with a work-up using 4-t-butylpyridine allowed us to improve the yield of the corresponding vinyl iodide compared to the previous procedures.
Synthesis of (E)-α,β-unsaturated esters and (Z)-vinyl halides with total or high diastereoselectivity by using samarium metal
Concellon, Jose M.,Rodriguez-Solla, Humberto,Huerta, Monica,Perez-Andres, Juan A.
, p. 1839 - 1847 (2007/10/03)
A highly diastereoselective β-elimination of 2-halo-3-hydroxy esters 1 or O-acetylated 1,1-dihaloalkan-2-ols 4 is achieved with samarium in the presence of diiodomethane, yielding α,β-unsaturated esters 2 or vinyl halides 5, respectively. The β-elimination reaction was promoted by samarium diiodide, which was generated in situ. The starting halohydrins 1 or 4 are easily prepared by reaction of the corresponding lithium enolates of α-halo esters or dihalomethyllithium with aldehydes at -78°C. The influence of the reaction conditions and the structure of the starting compounds on the diastereoselectivity of the β-elimination reactions is discussed, A comparative study of the β-elimination reaction with preformed SmI2 and metallic samarium is also performed. These elimination reactions can be explained by the proposed mechanism. Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).
