4096-34-8Relevant academic research and scientific papers
Construction of bicyclic systems containing an oxygen bridge by isomerization of cyclic epoxy alcohols
Iwakura, Masaru,Tokura, Hiroshi,Tanino, Keiji
, p. 1223 - 1226 (2017)
A novel method for constructing a 7-oxabicyclo[2.2.1]heptane skeleton was developed. The substrates, namely cis-3,4-epoxy-1-cyclohexanol derivatives, were prepared from the corresponding 3-cyclohexen-1-ol derivatives via a stereoselective epoxidation reaction using a vanadium catalyst. Upon heating with lithium iodide in propionitrile, the cis-epoxy alcohol was transformed into the 7-oxabicyclo[2.2.1]heptane derivative in high yield. The reaction proceeds through formation of a lithium alkoxide bearing an iodohydrin moiety, followed by an intramolecular SN2 reaction.
Chiral Supramolecular U-Shaped Catalysts Induce the Multiselective Diels-Alder Reaction of Propargyl Aldehyde
Hatano, Manabu,Sakamoto, Tatsuhiro,Mizuno, Tomokazu,Goto, Yuta,Ishihara, Kazuaki
supporting information, p. 16253 - 16263 (2018/11/27)
The Diels-Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon-carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewis acid catalysts promote the unprecedented multiselective Diels-Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate control, enantio-, endo/exo-, π-facial-, regio-, site-, and substrate-selectivities could be controlled by the present U-shaped catalysts. The obtained reaction products could access the concise synthesis of chiral diene ligands and a key intermediate of (+)-sarkomycin. The results presented here might partially contribute to the development of artificial enzyme-like supramolecular catalysts for multiselective reactions, which will be able to target organic compounds that have thus far eluded synthesis.
Highly Enantioselective Construction of Hajos-Wiechert Ketone Skeletons via an Organocatalytic Vinylogous Michael/Stetter Relay Sequence
Jia, Zhi-Long,Wang, Yao,Zhao, Chuan-Gang,Zhang, Xiao-Hai,Xu, Peng-Fei
supporting information, p. 2130 - 2133 (2017/04/27)
A highly enantioselective supramolecular iminium-catalyzed vinylogous Michael addition/Stetter relay sequence has been developed. This transformation provided a series of Hajos-Wiechert-type fused bicyclic diones with three continuous stereogenic centers in good yields with excellent enantioselectivities. The obtained products can be easily transformed into other structures with potential synthetic value.
Comparison of the singlet oxygen ene reactions of cyclic versus acyclic β,γ-unsaturated ketones: An experimental and computational study Dedicated to Professor Waldemar Adam on the occasion of his 75th birthday
Griesbeck, Axel G.,Goldfuss, Bernd,Leven, Matthias,De Kiff, Alan
supporting information, p. 2938 - 2941 (2013/06/27)
The photooxygenation of two β,γ-unsaturated ketones was studied by experimental and computational methods: 5-methyl-hex-4-en-2-one (1) and cyclohex-3-en-1-one (6) as model compounds for acyclic versus cyclic deconjugated enones. The open-chain substrate delivered a 1:1 mixture of regioisomers 2a,b following the established cis-selectivity model whereas the cyclic substrate reacts with 1O2 to give preferentially the conjugated product 7. This effect is in agreement with the mechanistic two-stage no-intermediate model and on a computational level corresponds to a regioselectivity control following the steepest decent pathway from the corresponding transition stages in a valley ridge potential energy surface region.
Direct oxidative allylic and vinylic amination of alkenes through selenium catalysis
Trenner, Johanna,Depken, Christian,Weber, Thomas,Breder, Alexander
supporting information, p. 8952 - 8956 (2013/09/02)
Bringing "N" into the game: The direct chemoselective nitrogenation of unactivated alkenes can be achieved through oxidative selenium catalysis (see scheme). This method provides a broad variety of allylic imides in yields of up to 89 % using N-fluorobenzenesulfonimide (NFSI) as the terminal oxidant and nitrogen source. Furthermore, an unprecedented selenium-catalyzed vinylic C(sp2)-H nitrogenation was discovered. Copyright
Synthesis of oxazole analogs of streptolidine lactam
Rynearson, Kevin D.,Dutta, Sanjay,Tran, Kiet,Dibrov, Sergey M.,Hermann, Thomas
, p. 7337 - 7342 (2013/11/19)
The streptolidine lactam is an amino acid constituent of streptothricin antibiotics, which inhibit protein synthesis by targeting the bacterial ribosome but suffer from toxicity as a result of the basicity of the aminoimidazole scaffold in the natural products. On the basis of the streptolidine structure, we designed and synthesized oxazole analogs with six- and seven-membered lactam rings as building blocks for RNA-targeted ligands. These analogs benefit from a dense network of hydrogen-bond donors and acceptors within a rigid nonplanar heterocyclic system that has attenuated basicity. Oxazole analogs based on the streptolidine scaffold of natural RNA-binding streptothricin antibiotics were designed and synthesized as building blocks for RNA-targeted ligands. These synthetic analogs with six- and seven-membered lactam rings benefit from a dense network of hydrogen-bond donors and acceptors within a rigid nonplanar heterocyclic system that has attenuated basicity. Copyright
Mn(III) complexes with tridentate N,N,O-ligands as catalysts for the epoxidation of alkenes
Aghmiz,Mostfa,Iksi,Rivas,Gonzalez,Diaz,El Guemmout,El Laghdach,Echarri,Masdeu-Bulto
, p. 2567 - 2577 (2013/08/23)
Mn(III) complexes with tridentate Schiff bases have been prepared and applied as catalyst precursors in epoxidation of alkenes using iodosobenzene as an oxidant providing high conversions and high selectivities when cyclohexene derivatives were studied.
Temporary thio-derivatization in the synthesis of (+)-4-acetylbromoxone
O'Byrne, Aisling,O'Reilly, Steven,Tighe, Catherine,Evans, Paul,Ciuffini, Laura,Gabriella Santoro
, p. 5936 - 5938 (2013/01/13)
A stereocontrolled synthesis of the marine natural products (+)-bromoxone (1) and (+)-4-acetylbromoxone (2) is reported. The sequence features the enzymatic kinetic resolution of 4-hydroxycyclohexenone (6) via its S-benzyl adduct. Thereafter, a base-mediated elimination-silylation generated an optically active (-)-4S-4-tert-butyldimethylsilyoxycyclohexenone (5), which then underwent diastereoselective epoxidation. Saegusa-Ito oxidation enabled formation of the corresponding α,β-unsaturated ketone 13. Bromination-elimination and subsequent removal of the silicon protecting group afforded (+)-bromoxone (1) which was converted into (+)-(4S,5R,6R)-4-acetoxy-2- bromo-5,6-epoxycyclohex-2-enone (2) [(+)-4-acetylbromoxone]. Using a luciferase gene reporter assay ED50 for NFκB inhibition of 9 μM was determined.
Hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine
Goldsmith, Christian R.,Coates, Cristina M.,Hagan, Kenton,Mitchell, Casey A.
body text, p. 24 - 30 (2011/04/22)
Non-heme iron halogenases, such as SyrB2 and CytC3, catalyze the regioselective chlorination and bromination of aliphatic C-H bonds. Reported here is the hydrocarbon chlorination promoted by manganese and iron complexes with methylated derivatives of bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen). The reactions between these coordination compounds and meta-chloroperbenzoic acid generate oxidants capable of oxidizing weak C-H bonds to C-Cl bonds. This chemistry is regioselective, with a strong preference for activating C-H bonds on secondary carbons over weaker C-H bonds on tertiary carbons. The reactivity is consistent with the methyl groups on the ligands preventing more sterically encumbered substrates from accessing the reactive portions of a [MIV(LMen)(O)Cl2] oxidant. The iron compounds promote more hydrocarbon chlorination than their manganese analogs.
The thio-adduct facilitated, enzymatic kinetic resolution of 4-hydroxycyclopentenone and 4-hydroxycyclohexenone
O'Byrne, Aisling,Murray, Cian,Keegan, Dearbhla,Palacio, Carole,Evans, Paul,Morgan, Ben S.
supporting information; experimental part, p. 539 - 545 (2010/05/11)
The addition of 3,4-dimethoxybenzyl thiol 8, as a benzyl thiol surrogate, to racemic 4-hydroxycyclopent-2-enone 2 and 4-hydroxycyclohex-2-enone 15 gave the corresponding cis-adducts (±)-3-(3,4-dimethoxybenzylthio)-4- hydroxycyclopentanone 4b and (±)-3-(3,4-dimethoxybenzylthio)-4- hydroxycyclohexanone 16 with good diastereocontrol. In both cases, subsequent treatment with vinyl acetate, in the presence of a lipase enabled enantiomer resolution. Thus, (+)-16 and the acetate of its enantiomer, (-)-(1R,2S)-2-(3,4- dimethoxybenzylthio)-4-oxocyclohexyl acetate, (-)-17 were isolated in 98% enantiomeric excess. Based on the 1,4-dioxygenation pattern, (-)-17 can be used to prepare both enantiomers of 4-(tert-butyldimethylsilyloxy)cyclohex-2-enone 19. Firstly, saponification, with a sub-stoichiometric amount of NaOMe, followed by a one-pot silyl ether formation-sulfide elimination sequence gave (+)-19. Then using the same starting material a 6-step sequence, featuring a diastereoselective NaBH4 reduction and a Cope-type sulfoxide elimination, gave (-)-19.
