Synthesis of Azocane- and Oxocane-Annulated Furans by a [2+2] Photocycloaddition–Ring-Opening Cascade

Synthesis ◽  
2020 ◽  
Author(s):  
Thorsten Bach ◽  
Xinyao Li ◽  
Christian Jandl
Keyword(s):  
Double Bond ◽  
Uv Irradiation ◽  
Alkyl Group ◽  
Ring Opening ◽  
Cascade Reaction ◽  
Coumarin Derivatives ◽  
Ring Opening Reaction ◽  
Acid Catalyzed ◽  
Subsequent Acid

AbstractThe title compounds were synthesized from readily available quinolone and coumarin derivatives by a cascade reaction (12 examples, 90–98% yield). The cascade comprised a [2+2] photocycloaddition which occurred upon sensitized irradiation at λ = 420 nm (or direct UV irradiation at λ = 366 nm) and a subsequent acid-catalyzed ring-opening reaction. A variety of substituents are compatible with the conditions and a 3-alkyl group in the coumarin (or quinolone) is crucial to achieve a high chemoselectivity. Key to the success of the ring opening is the formation of a 4,5,5a-trihydrocyclobuta-2H-furan containing a strained bridgehead double bond which stems from the allenyl group tethered to the 4-position of the starting materials.

Cut and sew: benzofuran-ring-opening enabled cyclopentenone ring formation

2020 ◽  
Vol 56 (84) ◽  
pp. 12817-12820
Author(s):  
Kai Wang ◽  
Chenghao Jiang ◽  
Zhenming Zhang ◽  
Chunyu Han ◽  
Xuewei Wang ◽  
...  
Keyword(s):  
Ring Opening ◽  
Cascade Reaction ◽  
Ring Formation ◽  
Acid Catalyzed

A broad range of fully substituted cyclopentenones are constructed efficiently via an acid catalyzed cascade reaction involving an unprecedented benzofuran-ring-opening.

scholarly journals Torquoselectivity of the Ring-Opening Reaction of 3,3-Dihalosubstituted Cyclobutenes: Lone Pair Repulsion and Cyclic Orbital Interaction

2019 ◽  
Author(s):  
Yuji Naruse ◽  
Atsushi Takamori
Keyword(s):  
Double Bond ◽  
Ring Opening ◽  
Lone Pair ◽  
Repulsive Interaction ◽  
Orbital Interaction ◽  
Ring Opening Reaction ◽  
Ring Opening Reactions ◽  
Major Factors ◽  
Vacant Orbital ◽  
Model Reactions

<div><div>Three major factors determine torquoselectivity, which is the diastereoselectivity in electrocyclic ring-opening reactions to produce <i>E</i>/<i>Z</i>-double bond(s). One is the interaction between the decomposing s<sub>CC</sub> bond and low-lying vacant orbital(s), such as a p*- or s*-orbital on the substituent, which promotes the reaction, resulting in inward rotation of the substituent. Second, for a substituent with a lone pair(s), repulsive interaction between the decomposing s-bond and the lone pair(s) hinders inward rotation, so that the products of outward rotation should be preferred. Finally, a more strongly donating s-electron-donating group (sEDG) rotates inwardly due to stabilization by phase-continuous cyclic orbital interaction. We compared the latter two interactions, repulsion between the lone pairs on the substituent and stabilization from phase-continuous cyclic orbital interaction, to determine which has a greater effect on the diastereoselectivity. We considered a series of model reactions with halogen substituents, and concluded that the diastereoselectivity is mainly controlled by cyclic orbital interaction.<br></div></div>

Record-Breaking Steric Crowding in Trialkylamines Prepared by Oxidative Ring Opening

Synthesis ◽  
2020 ◽  
Vol 52 (24) ◽  
pp. 3801-3810
Author(s):  
Klaus Banert ◽  
Manuel Heck ◽  
Andreas Ihle ◽  
Erik Michael ◽  
Richard Weber
Keyword(s):  
Ring Opening ◽  
Room Temperature ◽  
Osmium Tetroxide ◽  
Model Compound ◽  
Ring Cleavage ◽  
Open Chain ◽  
Tert Butyl ◽  
Steric Crowding ◽  
Acid Catalyzed ◽  
Subsequent Acid

AbstractEpoxidation of olefinic heterocyclic amines and subsequent acid-catalyzed hydrolysis or alternatively the direct dihydroxylation with the help of osmium tetroxide led to diols, which underwent ring cleavage in the presence of lead tetraacetate to give 3-isopropyl-2,2,4,4-tetramethyl-3-azahexanedial and 3-tert-butyl-2,2,4,4-tetramethyl-3-azapentanedial. Whereas the former dialdehyde is a highly unstable model compound because of a rapid intramolecular aldol reaction, the latter product proves to be isolable at room temperature. Furthermore, this compound is the first open-chain tri-tert-alkylamine establishing in a new record of steric crowding in tertiary amines. Strong tendencies to a Hofmann-like elimination reaction or to ring-closing reactions were observed when the aldehyde units of 3-tert-butyl-2,2,4,4-tetramethyl-3-azapentanedial were transformed into other functionalities, since both types of reactions led to a significantly decrease of the steric stress.

Synthesis of Polycyclic Spiroindolines via the Cascade Reaction of 3-(2-isocyanoethyl)Indoles

2021 ◽  
Author(s):  
Haizhen Li ◽  
Jinyu Wu ◽  
Jianfeng Zheng ◽  
Wei-Dong Z. Li
Keyword(s):  
Ring Opening ◽  
Cascade Reaction ◽  
Tandem Reactions ◽  
Ring Opening Reaction

Tandem reactions of Yttrium(III) catalyzed ring-opening reaction of 2,2’-diester aziridines with 3-(2-isocyanoethyl)indoles and subsequent Friedel-Crafts/Mannich/desulfonylation were reported. A series of polycyclic spiroindolines containing tetrahydro-β-carbonlines were obtained in moderate to excellent...

scholarly journals Non-Isocyanate Polyurethane (NIPU) based on Rubber Seed Oil Synthesized via Low-Pressured Carbonization Reaction

2021 ◽  
Vol 50 (8) ◽  
pp. 2407-2417
Author(s):  
R.A. Hambali ◽  
M.A. Faiza ◽  
A. Zuliahani
Keyword(s):  
Hydrogen Peroxide ◽  
Double Bond ◽  
Formic Acid ◽  
Ring Opening ◽  
Seed Oil ◽  
Epoxide Ring ◽  
Rubber Seed Oil ◽  
Rubber Seed ◽  
Ring Opening Reaction ◽  
Epoxidation Reaction

Epoxidised rubber seed oil (ERSO) was successfully synthesized into non-isocyanate polyurethane via carboxylation method whereas peroxoformic acid was formed by in-situ reaction for epoxidation. The effects of temperature and ratio of hydrogen peroxide and formic acid to rubber seed oil carboxylation were studied. The optimum temperature for the epoxidation reaction was found at 50 °C to avoid ring opening reaction of epoxy whilst the optimum ratio of hydrogen peroxide and formic acid is equal molar of double bond: formic acid at 1:2 and 1:1, respectively. At a lower concentration of hydrogen peroxide and formic acid, the oxirane ring was stable due to the lower hydrolysis (oxirane cleavage) of an epoxide. The effect of using low content of formic acid tends to minimize unwanted epoxide ring opening to occur and make the epoxidation rate increased with increasing of oxirane number. Fourier transform infrared (FTIR) spectral displayed the presence of an epoxy functional group at 822 cm-1 and the disappearance of double bond peak at 3011 cm-1 corresponding to epoxidised oil and carbonyl group confirmed the epoxidation reaction had taken place. 1H-NMR was used to confirm the formation of carboxylate functionality after the reaction of epoxy at δ 4.83 and 4.61 ppm. In conclusion, ERSO has great potential to be used as a precursor in producing environmentally friendly non-isocyanate polyurethane.

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