7642-11-7Relevant academic research and scientific papers
Ligand-controlled cobalt-catalyzed regiodivergent hydroboration of aryl,alkyl-disubstituted internal allenes
Ge, Shaozhong,Wu, Caizhi
, p. 2783 - 2789 (2020/03/24)
We report a stereoselective regiodivergent hydroboration of aryl,alkyl-disubstituted internal allenes with pinacolborane (HBpin) in the presence of cobalt catalysts generated from bench-stable Co(acac)2 and bisphosphine ligands. An interesting correlation between the regioselectivity of this hydroboration and the bite angles of bisphosphine ligands was identified. When hydroboration was conducted with cobalt catalysts containing bisphosphines with medium bite angles (e.g. 98° for dppb and 96° for dppf), HBpin was selectively added to the alkyl-substituted double bond. However, HBpin was selectively added to the aryl-substituted double bond when the reactions were conducted with cobalt catalysts containing bisphosphines with large bite angles (e.g. 111° for xantphos and 114° for Nixantphos). A range of internal allenes underwent these Co-catalyzed hydroboration reactions in a regiodivergent manner to yield the corresponding (Z)-alkenylboronates in high isolated yields and with high regioselectivity. These reactions show good functional group compatibility and can be readily scaled up to gram scales without using a dry box. In addition, the comparison of regioselectivity between the Co-catalyzed hydrosilylation and hydroboration reactions of the same allene substrate suggests that this Co-catalyzed regiodivergent hydroboration of allenes proceeds through a Co-Bpin intermediate. Deuterium-labeling experiments suggest that the Co-Bpin intermediates react with allenes to form allylcobalt species which then react with HBpin to release (Z)-alkenylboronate products.
Orthogonally protected 1,2-diols from electron-rich alkenes using metal-free olefin syn-dihydroxylation
Colomer, Ignacio,Barcelos, Rosimeire Coura,Christensen, Kirsten E.,Donohoe, Timothy J.
supporting information, p. 5880 - 5883 (2016/11/29)
A new method for the stereoselective metal-free syn-dihydroxylation of electron-rich olefins is reported, involving reaction with TEMPO/IBX in trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) and the addition of a suitable nucleophile. Orthogonally
Photocatalytic synthesis of dihydrobenzofurans by oxidative [3+2] cycloaddition of phenols
Blum, Travis R.,Zhu, Ye,Nordeen, Sarah A.,Yoon, Tehshik P.
supporting information, p. 11056 - 11059 (2015/03/30)
We report a protocol for oxidative [3+2] cycloadditions of phenols and alkenes applicable to the modular synthesis of a large family of dihydrobenzofuran natural products. Visible-light-activated transition metal photocatalysis enables the use of ammonium persulfate as an easily handled benign terminal oxidant. The broad range of organic substrates that are readily oxidized by photoredox catalysis suggests that this strategy may be applicable to a variety of useful oxidative transformations.
Stereochemistry of direct olefin formation from carbonyl compounds and lithiated heterocyclic sulfones
Baudin, J. B.,Hareau, G.,Julia, S. A.,Lorne, R.,Ruel, O.
, p. 856 - 878 (2007/10/02)
The conditions for the title reaction were studied for the 2-benzothiazole and 2-pyridine series and for some examples in the 2-pyrimidine series.The olefin preparations were generally observed to be more efficient for 2-BT-sulfone systems.From the data of the hundred cases studied, it can be concluded that (E)-olefins are obtained: (i) from saturated BT-sulfones and aromatic aldehydes; and (ii) from benzylic BT-sulfones and branched saturated aldehydes (isobutyraldehyde, pivalaldehyde) or α,β-ethylenic or aromatic aldehydes. (Z)-olefins arise: (i) fom propargylic BT-sulfones and saturated or aromatic aldehydes; and (ii) from allylic or benzylic Pyr-sulfones and saturated aldehydes.Possible mechanisms for this new olefination procedure were examined. - heteroaromatic sulfones, organolithium derivatives, intramolecular ipso reactions, stereochemistry, elimination, olefination.
Protonation and Alkykation of 1-Arylpropenyl-lithium
Tanaka, Jiro,Nojima, Masatomo,Kusabayashi, Shigekazu,Nagase, Shigeru
, p. 673 - 678 (2007/10/02)
The protonation and alkylation of 1-arylpropenyl-lithium (1a-c) in ether was undertaken systematically; the regio- and stereo-chemistry being influenced by various factors.The characteristic features are as follows. (a) Protonation occurs predominantly at C-3, whereas the sterically more crowded C-1 is the more favoured site for alkylation, and (b) although 1-arylpropenyl-lithium (1) seems to exist mainly as the E-isomer, in some cases the product (3) or (5) having the Z-configuration is produced from attack at C-3 in a significant amount together with the E-isomer, e.g. protonation by oxygen acids in the presence or absence of tetramethylethylenediamine and methylation of the p-methoxy derivative (1a).
REACTIONS EN MILIEU HETEROGENE SOLIDE-LIQUIDE FAIBLEMENT HYDRATE III - LA REACTION DE WITTIG DANS LE SYSTEME CARBONATES ALCALINS/SOLVANT ORGANIQUE PROTIQUE
Le Bigot, Y.,El Gharbi, R.,Delmas, M.,Gaset, A.
, p. 3813 - 3824 (2007/10/02)
The use of alkaline carbonates in a slighty hydrated solid-liquid protic organic media allowed the synthesis of alkenes from polyfunctional aldehydes with high yield in a E preferential stereochemistry specially with non-stabilized ylides.It has been shown that the decomposition of the threo betain acts as the determining step of the reaction.
Alkenyl-copper derivatives 19. Synthesis of conjugated dienes and styrenes by cuopling of alkenyl cuprates with alkenyl and aryl halides
Jabri, N.,Alexakis, A.,Normant, J. F.
, p. 321 - 331 (2007/10/02)
Z dialkenylcuprates obtained by carbometallation of acetylene couple easily with alkenylhalides and iodoarenes in the presence of ZnBr2 and a catalytic amount of NiL4 or Pd0L4 to afford high yields of conjugated dienes and styrenes with very high stereoselectivity.Such pure dienes are often encountered in insect sex pheromones.
