29108-24-5Relevant academic research and scientific papers
Primary Anion–π Catalysis of Epoxide-Opening Ether Cyclization into Rings of Different Sizes: Access to New Reactivity
Matile, Stefan,Paraja, Miguel
supporting information, p. 6273 - 6277 (2020/02/28)
The concept of anion–π catalysis focuses on the stabilization of anionic transition states on aromatic π surfaces. Recently, we demonstrated the occurrence of epoxide-opening ether cyclizations on aromatic π surfaces. Although the reaction proceeded through unconventional mechanisms, the obtained products are the same as those from conventional Br?nsted acid catalysis, and in agreement with the Baldwin selectivity rules. Different mechanisms, however, should ultimately lead to new products, a promise anion–π catalysis has been reluctant to live up to. Herein, we report non-trivial reactions that work with anion–π catalysis, but not with Br?nsted acids, under comparable conditions. Namely, we show that the anion–π templated autocatalysis and epoxide opening with alcoholate–π interactions can provide access to unconventional ring chemistry. For smaller rings, anion–π catalysis affords anti-Baldwin oxolanes, 2-oxabicyclo[3.3.0]octanes, and the expansion of Baldwin oxetanes by methyl migration. For larger rings, anion–π templated autocatalysis is thought to alleviate the entropic penalty of folding to enable disfavored anti-Baldwin cyclizations into oxepanes and oxocanes.
NHC-Ni(0) Catalyzed Diastereodivergent Hydroacylative Enyne Cyclization: Synthesis of Heterocycles bearing γ-Enone
Yong, Xuefeng,Ng, Elvis Wang Hei,Zhen, Zibo,Lin, Xiulian,Gao, Weiwei,Ho, Chun-Yu
supporting information, p. 4164 - 4172 (2020/08/26)
NHC-Nickel(0) catalyzed 1,3- and 1,4-diastereodivergent hydroacylative heteroenyne cyclization with aldehydes was achieved (Syn-:Anti-, switchable from up to 1:99 to 98:2). Both sets of heterocyclic diastereomers are accessible via this route, with a high
α-Branched Ketone Dienolates: Base-Catalysed Generation and Regio- and Enantioselective Addition Reactions
Urruzuno, I?aki,Mugica, Odei,Zanella, Giovanna,Vera, Silvia,Gómez-Bengoa, Enrique,Oiarbide, Mikel,Palomo, Claudio
supporting information, p. 9701 - 9709 (2019/07/12)
In this study, the unique capacity of bifunctional Br?nsted bases to generate α-branched ketone dienolates and control both site- and stereoselectivity of their addition reactions to representative classes of carbon electrophiles (i.e., vinyl sulfones, nitroolefins, formaldehyde) is documented. We demonstrate that by using selected chiral tertiary amine/squaramide catalysts, the reactions of β,γ-unsaturated cycloalkanones proceed through the dienolate Cα almost exclusively and provide all-carbon quaternary cyclic ketone adducts in good yields with very high enantioselectivities. A minor amount (5 %) of γ-addition is observed when nitroolefins are used as electrophiles. The parent acyclic ketone dienolates proved to be less reactive under these conditions, and thus still constitute a challenging class of substrates. Quantum chemical calculations correctly predict these differences in reactivity and explain the observed site-specificity and enantioselectivity.
Stereoselective synthesis of α-methyl and α-alkyl ketones from esters and alkenes: Via cyclopropanol intermediates
Barysevich, Maryia V.,Kazlova, Volha V.,Kukel, Aliaksandr G.,Liubina, Aliaksandra I.,Hurski, Alaksiej L.,Zhabinskii, Vladimir N.,Khripach, Vladimir A.
supporting information, p. 2800 - 2803 (2018/03/21)
Alkenes bearing a stereocenter in the allylic position were found to undergo Kulinkovich hydroxycyclopropanation with good diastereoselectivity. For the isomerization of the resulting cyclopropanols to diastereomerically enriched α-methyl ketones, a new mild regioselective method has been developed. A sequence of stereoselective cyclopropanation and cyclopropanol ring opening was successfully employed for the construction of the C20 stereocenter in steroids.
The prins reaction using ketones: Rationalization and application toward the synthesis of the portentol skeleton
Jacolot, Maiwenn,Jean, Mickael,Levoin, Nicolas,Van De Weghe, Pierre
supporting information; experimental part, p. 58 - 61 (2012/02/14)
We report a TMSI-promoted Prins cyclization reaction with ketones as carbonyl partners to prepare polysubstituted chiral spirotetrahydropyrans. In the presence of racemic 2-methylcyclohexanone a dynamic kinetic resolution occurred affording one stereoisom
Prins fluorination cyclisations: Preparation of 4-fluoro-pyran and -piperidine heterocycles
Launay, Guillaume G.,Slawin, Alexandra M. Z.,O'Hagan, David
supporting information; experimental part, (2010/08/07)
The Prins reaction was investigated using BF3OEt2 as a Lewis acid. It has been recently demonstrated, that if BF3OEt2 is used in stoichiometric amounts then these reactions generate fluorinated products where the BF3OEt2 contributes fluoride ion to quench the intermediate carbocations. In this study oxa- and aza-Prins reactions for the synthesis of 4-fluoro-pyrans and -piperidines were investigated. The products were obtained in good yields, but only with moderate diastereoselectivity. These Prins fluorination reactions can be accelerated under microwave conditions. The study extends the Prins fluorination methodology for the generation of the C-F bond in heterocycles.
Pd(OAc)2/P(cC6H11) 3-catalyzed allylation of aryl halides with homoallyl alcohols via retro-allylation
Iwasaki, Masayuki,Hayashi, Sayuri,Hirano, Koji,Yorimitsu, Hideki,Oshima, Koichiro
, p. 4463 - 4469 (2008/02/04)
Allylations of aryl halides take place upon treatment of tertiary homoallyl alcohols with aryl halides in the presence of cesium carbonate and a palladium catalyst. The allylation reaction would consist of the following steps: (1) oxidative addition of ar
Diastereoselective palladium-catalyzed formate reduction of allylic carbonates en route to polypropionate systems
Chau, Anh,Paquin, Jean-Francois,Lautens, Mark
, p. 1924 - 1933 (2007/10/03)
Diastereoselective palladium-catalyzed formate reduction of allylic carbonates presents unique opportunities for applications in target-oriented organic synthesis provided that selectivity, in particular stereoselectivity, in the course of this metal-cata
Gold-catalyzed synthesis of substituted tetrahydronaphthalenes
Grise, Christiane M.,Barriault, Louis
, p. 5905 - 5908 (2007/10/03)
(Diagram presented) We report a gold-catalyzed benzannulation of 3-hydroxy-1,5-enynes to generate tetrahydronaphthalenes. This mild process proves to be an effective method to synthesize various metasubstituted aromatic rings in good yields.
