18409-20-6Relevant articles and documents
Cobalt-Catalyzed Diastereo- And Enantioselective Reductive Allyl Additions to Aldehydes with Allylic Alcohol Derivatives via Allyl Radical Intermediates
Wang, Lei,Wang, Lifan,Li, Mingxia,Chong, Qinglei,Meng, Fanke
, p. 12755 - 12765 (2021/08/30)
Catalytic generation of ambiphilic π-allyl-metal complexes and their utility in enantioselective transformations constitutes a powerful approach for introduction of allyl groups to a molecule. Herein an unprecedented cobalt-catalyzed highly site-, diastereo-, and enantioselective protocol for stereoselective formation of nucleophilic allyl-Co(II) complexes followed by addition to aldehydes is presented. The reaction features diastereo- and enantioconvergent conversion of easily accessible allylic alcohol derivatives to diversified enantioenriched homoallylic alcohols with a remarkably broad scope of allyl groups that can be introduced. Mechanistic studies indicated that allyl radical intermediates were involved in this process. These new discoveries establish a new strategy for development of enantioselective transformations through capture of radicals by chiral Co complexes, pushing forward the frontier of Co complexes for enantioselective catalysis.
One Stone for Three Birds-Rhodium-Catalyzed Highly Diastereoselective Intramolecular [4+2] Cycloaddition of Optically Active Allene-1,3-dienes
Han, Yulin,Qin, Anni,Ma, Shengming
, p. 486 - 496 (2019/04/04)
RhCl(PPh3)3-catalyzed [4+2] intramolecular cycloaddition of optically active axially chiral allene-dienes afforded cis-fused [3.4.0]-bicyclic products with three chiral centers in good yields with an excellent chemo- and diastereoselectivity. A pair of enantiomers of such products was generated highly selectively from both enantiomers of starting allene-dienes, indicating that the axial chirality dictated the absolute configurations of the three in situ generated chiral centers with a very high efficiency of chirality transfer.
Cobalt-catalyzed versus uncatalyzed intramolecular Diels-Alder cycloadditions
Biletskyi, Bohdan,Tenaglia, Alphonse,Clavier, Hervé
supporting information, p. 103 - 107 (2017/12/28)
The intramolecular [4+2] cycloadditions of dienynes was investigated using cobalt-based catalysts. Substrates without substitution on alkyne moiety were found to react under thermal activation. The use of a cobalt salt as catalyst made reactions cleaner by limiting the formation of byproducts. Cycloadditions with dienynes possessing a substituent on the alkyne pattern occurred only in presence of a cobalt catalyst which displayed a moderate to good activity depending on the substrate patterns.
The asymmetric aza-claisen rearrangement: development of widely applicable pentaphenylferrocenyl palladacycle catalysts
Fischer, Daniel F.,Barakat, Assem,Xin, Zhuo-Qun,Weiss, Matthias E.,Peters, Rene
supporting information; experimental part, p. 8722 - 8741 (2010/03/31)
Systematic studies have been performed to develop highly efficient catalysts for the asymmetric aza-Claisen rearrangement of trihaloacetimidates. Herein, we describe the stepwise development of these catalyst systems involving four different catalyst generations finally resulting in the development of a planar chiral pentaphenylferrocenyl oxazoline palladacycle. This complex is more reactive and has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza-Claisen rearrange-ments. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza-Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines, but also secondary and tertiary amines; al-lylic amines with N-substituted quaternary stereocenters are conveniently accessible as well. The reaction conditions tolerate many important functional groups, thus providing stereoselective access to valuable functionalized building blocks, for example, for the synthesis of unnatural amino acids. Our results suggest that face-selective olefin coordination is the enantioselectivitydetermining step, which is almost exclusively controlled by the element of planar chirality.
Aggregation behavior of tetraenoic fatty acids in aqueous solution
Wang, Yonghui,Ma, Jianguo,Cheon, Hwan-Sung,Kishi, Yoshito
, p. 1333 - 1336 (2008/04/05)
(Chemical Equation Presented) Why so blue? Unique blue-shifted UV absorptions were used to follow the aggregation of C24 tetraene fatty acids in aqueous solution. Aggregation takes place through three distinct states (i.e. K→T1→T2; see picture). It is suggested that all of these aggregates are lamellar-type in a local sense but differ in the packing mode of the fatty acid backbone.
Candidate trail attractants of Reticultermes lucifugus: Stereoselective syntheses of (3Z, 6E, 8E)- (3Z, 6E, 8Z)- and (3Z, 6Z, 8Z)-3,6,8-dodecatrien-1-ol
Bellina, Fabio,Carpita, Adriano,Corradi, Chiara,Rossi, Renzo
, p. 3297 - 3316 (2007/10/03)
Stereoselective syntheses on a gram scale of (3Z,6E,8E)-, (3Z,6E,8Z)- and (3Z,6Z,8Z)-3,6,8-dodecatrien-1-ol, 8, 9 and 10, respectively, are described. A key step of the synthesis of 8 consisted of a copper-mediated coupling reaction between 4-(2-tetrahydropyranyloxy)-1-butynylmagnesium bromide (15) and the mesyl ester of (2E,4E)-2,4-octadien-1-ol (14). A similar copper-mediated reaction between 15 and the mesyl ester of (E)-2-octen-4-yn-1-ol (19) was used to construct the C-12 carbon skeleton of 9. On the other hand, the synthesis of 10 was based on a palladium-promoted reaction between (Z)-1-bromo-1-pentene (23) and the organozinc bromide derived from 3,6-heptadiyn-1-yl acetate (27).
COMPOUNDS WITH A HERBAL ODOR III. CIS-ALKENES WITH AN OXYGEN FUNCTION AT THE β POSITION AND THEIR SYNTHESIS BY HYDROGENATION OF DIENE PRECURSORS AT CHROMIUM HEXACARBONYL
Vasil'ev, A. A.,Cherkaev, G. V.
, p. 834 - 840 (2007/10/02)
During the hydrogenation of dienes with oxygen functions at the α position in the presence of chromium hexacarbonyl 1,4-addition of hydrogen to the diene system occurs, and this leads to the corresponding cis-monoene derivatives.In the case of dienes with hydroxyl, alkoxyl, acetal, and ester groups the product yield approaches quantitative; the hydrogenation of similar oxo and acyloxy derivatives is less satisfactory.Many representatives of the synthesized compounds, in which the cis-disubstituted double bond is separated from the oxygen-containing functional group by two carbon atoms, have a herbal odor.
