6376-95-0Relevant 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
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.
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
Ketyl-allene cyclizations promoted by samarium(II) iodide
Molander, Gary A.,Cormier, Elizabeth Pollina
, p. 2622 - 2626 (2007/10/03)
(Chemical Equation Presented) Samarium(II) iodide has proven to be an effective reagent for intramolecular reductive coupling Sreactions. Previous investigations of intramolecular ketyl-olefin coupling reactions provided carbocycles in excellent yield and good diastereoselectivity. This method has been extended to ketyl cyclizations with allenes. Substrates leading to both carbocycles and heterocycles in a selective manner are explored.
Conformational effects on lipase-mediated acylations of 2-substituted cyclohexanols
Tanikaga, Rikuhei,Matsumoto, Yoshimasa,Sakaguchi, Maki,Koyama, Yohei,Ono, Kentaro
, p. 6781 - 6783 (2007/10/03)
Lipase-mediated acetylations of trans- and cis-2-substituted cyclohexanols gave the corresponding (1R)-cyclohexyl acetates and (1S)-cyclohexanols in high yields and ee, but c-4-tert-butyl-c-2-ethenyl-r-1-cyclohexanol was unreactive owing to the steric interaction between the axial OH group and the axial H atoms at the 3- and 5-positions. In the cis-isomer the OH group occupies an equatorial position to bind to the lipase, and less bulky axial alkenyl and alkynyl groups might not so much prevent acetylations than an alkyl group.
Synthesis of diastereomerically enriched cyclic homoallylic alcohols using molybdenum π-allyl complexes
Krafft, Marie E.,Schmidt, Peter
, p. 2723 - 2732 (2007/10/03)
Condensation of CpMo(NO)(π-allyl)I complexes bearing a tethered aldehyde gave cyclic homoallylic alcohols with a varying degree of diastereoselectivity. Cyclohexyl and tetrahydronaphthyl derivatives were prepared in moderate to good yields. The diastereos
