scholarly journals Regioselective Synthesis of N-β-Hydroxyethylaziridines by the Ring-Opening Reaction of Epoxides with Aziridine Generated in situ.

ChemInform ◽  
2006 ◽  
Vol 37 (29) ◽  
Author(s):  
Ha Young Kim ◽  
Arindam Talukdar ◽  
Mark Cushman
Keyword(s):  
Ring Opening ◽  
Regioselective Synthesis ◽  
Ring Opening Reaction

Enantioselective ring opening of tropinone. A new entry into tropane alkaloids

1997 ◽  
Vol 75 (6) ◽  
pp. 754-761 ◽  
Author(s):  
Marek Majewski ◽  
Ryszard Lazny ◽  
Agnieszka Ulaczyk
Keyword(s):  
Ring Opening ◽  
Stereoselective Synthesis ◽  
Tropane Alkaloids ◽  
Amine Hydrochloride ◽  
Lithium Amides ◽  
Ring Opening Reaction ◽  
Alkyl Chloroformates ◽  
Optically Pure ◽  
Enantioselective Deprotonation

The lithium enolate of tropinone reacts with alkyl chloroformates to give 6-N-carboalkoxy-N-methyl-2-cycloheptenones (4). These compounds can be produced enantioselectively, in up to 95% ee, if chiral lithium amides (derived from optically pure amines 5–7) are used for deprotonation of tropinone in the presence of additives. The effect of additives such as LiCl, LiBr, LiF, LiClO4, CeCl3, ZnCl2, LiOH, TMEDA, HMPA, and DMPU on enantioselectivity of this deprotonation–ring opening sequence varies from slight to very large depending on the chiral amide – additive combination. Especially large increases in enantioselectivity are observed when the chiral, C2 symmetrical, lithium bis-α,α′-methylbenzylamide (Li-5a) is used with one equivalent of LiCl. This reagent is best generated in situ from the corresponding amine hydrochloride and n-BuLi (2 equiv.). The ring-opening reaction combined with transposition of the carbonyl group (via Wharton reaction or allylic oxidation) provides a new method of stereoselective synthesis of tropane alkaloids having a protected hydroxyl at C-6 or C-7 (6β- and 7β-acetoxytropanes 14a, b) and physoperuvine (19). Keywords: enantioselective deprotonation, tropane alkaloids.

scholarly journals PhSeZnCl in the Synthesis of Steroidal β-Hydroxy-Phenylselenides Having Antibacterial Activity

2019 ◽  
Vol 20 (9) ◽  
pp. 2121 ◽  
Author(s):  
Jastrzebska ◽  
Mellea ◽  
Salerno ◽  
Grzes ◽  
Siergiejczyk ◽  
...  
Keyword(s):  
Antibacterial Activity ◽  
Biofilm Formation ◽  
Ring Opening ◽  
Antibacterial Properties ◽  
Multidrug Resistant ◽  
Bacterial Biofilm ◽  
Resistant Bacteria ◽  
Multidrug Resistant Bacteria ◽  
Ring Opening Reaction

We report here the reaction of in situ prepared PhSeZnCl with steroid derivatives having an epoxide as an electrophilic functionalization. The corresponding ring-opening reaction resulted to be regio- and stereoselective affording to novel phenylselenium-substituted steroids. Assessment of their antibacterial properties against multidrug-resistant bacteria, such as Pseudomonas aeruginosa Xen 5 strain, indicates an interesting bactericidal activity and their ability to prevent bacterial biofilm formation.

Morphologies and Mechanical Properties of Epoxy Resin/Polymethyl Methacrylate Interpenetrating Network Modified with Kaolin

2011 ◽  
Vol 337 ◽  
pp. 184-187
Author(s):  
Gui Xiang Hou ◽  
Xiao Ai Chen ◽  
Xiao Ming Sang
Keyword(s):  
Epoxy Resin ◽  
Polymethyl Methacrylate ◽  
Ring Opening ◽  
Interpenetrating Network ◽  
Scanning Electronic Microscopy ◽  
Epoxy Ring ◽  
Ring Opening Reaction ◽  
Epoxy Ring Opening ◽  
Lower Tensile Strength

Epoxy resin/polymethyl methacrylate(EP/PMMA,70/30) interpenetrating network composites containing various contents of dimethyl sulfoxide modified kaoline (EP/PMMA /K-DMSO) composites were prepared by a sequential polymeric technique and an in situ intercalation method. FTIR results showed that the epoxy ring opening reaction occurs, the formation of IPN structure of PMMA and EP has been created. The structure of composite material was characterized by scanning electronic microscopy (SEM). The result indicated that higher impact strength and lower tensile strength with increasing concentration of K-DMSO.

C-H Bond Cleavage-Enabled Aerobic Ring-Opening Reaction of in Situ Formed 2-Aminobenzofuran-3(2H)-ones

2021 ◽  
Author(s):  
Yingwei Wang ◽  
Mingrong Yang ◽  
Chic Hou Lao ◽  
Zhi-Hong Jiang
Keyword(s):  
Ring Opening ◽  
Bond Cleavage ◽  
One Pot ◽  
Ring Opening Reaction ◽  
Alternative Approach

A C-H bond cleavage-enabled areobic ring-opening reaction of 2-aminobenzofuran-3(2H)-ones formed in situ by hemiacetals with a variety of amines is reported. The simple one-pot reaction provides an alternative approach to...

Synthesis and Self-assembly of Amphiphilic Hetero-arm Molecular Brushes

2011 ◽  
Vol 64 (8) ◽  
pp. 1100 ◽  
Author(s):  
Waled Hadasha ◽  
Mpho Mothunya ◽  
Niels Akeroyd ◽  
Bert Klumperman
Keyword(s):  
Self Assembly ◽  
Ring Opening ◽  
Alkyl Chain ◽  
Ring Closure ◽  
Molecular Brushes ◽  
Alkyl Amines ◽  
Ring Opening Reaction ◽  
Grafting From ◽  
Chain Lengths

We report the synthesis of amphiphilic hetero-arm molecular brushes (AMBs), which were prepared by a combination of ‘grafting from’ and ‘grafting onto’ methodologies. First, styrene-terminated polyethylene glycol macromonomer (VB-PEG12, ∼666 g mol–1) was copolymerized with maleic anhydride (MAnh) to yield a polymer containing hydrophilic PEG chains and reactive (MAnh) groups. Subsequently, the reactive MAnh units in the obtained polymer were modified via a ring-opening reaction using primary alkyl amines, with different alkyl chain lengths, as the nucleophile. In situ ring closure yielded the styrene–maleimide-based AMB. The amphiphilic character of the AMBs was used for their self-assembly in different solvents. The effect of the ratio in hydrophilic to hydrophobic graft length on the morphology of the assemblies was studied using scanning electron microscopy.

Surface engineering of low-fouling and hemocompatible polyethersulfone membranes via in-situ ring-opening reaction

2019 ◽  
Vol 581 ◽  
pp. 373-382 ◽  
Author(s):  
Haifeng Ji ◽  
Hao Xu ◽  
Lunqiang Jin ◽  
Xin Song ◽  
Chao He ◽  
...  
Keyword(s):  
Ring Opening ◽  
Surface Engineering ◽  
Ring Opening Reaction

Synthesis of poly(arylene disulfide)-vermiculite nanocomposites via in situ ring-opening reaction of cyclic oligomers

2003 ◽  
Vol 39 (8) ◽  
pp. 1735-1739 ◽  
Author(s):  
X.S. Du ◽  
M. Xiao ◽  
Y.Z. Meng ◽  
T.F. Hung ◽  
A.V. Rajulu ◽  
...  
Keyword(s):  
Ring Opening ◽  
Ring Opening Reaction ◽  
Cyclic Oligomers

On the Conrotatory Ring Opening of 3-Carbomethoxycyclobutene Vis-À-Vis 3-Carbomethoxy-1,2-Benzocyclobutene and the Predominant Inward Opening of 3-Dimethylaminocarbonyl-1,2-Benzocyclobutene

2018 ◽  
Author(s):  
Veejendra Yadav ◽  
Dasari L V K Prasad ◽  
Arpita Yadav ◽  
Maddali L N Rao
Keyword(s):  
Transition State ◽  
Ring Opening ◽  
Electron Process ◽  
Ring Opening Reaction ◽  
Stable Species ◽  
Electron Event

<p>The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by p<sub>C1C2</sub>→s*<sub>C3C4</sub> and s<sub>C3C4</sub>→p*<sub>CO</sub> interactions in the transition state in a 4-electron process as opposed to only s<sub>C3C4</sub>→p*<sub>CO</sub> interaction in an apparently 8-electron event in 3-carbomethoxy-1,2-benzocyclobutene. The ring opening of 3-carbomethoxy-1,2-benzocyclobutene is sufficiently endothermic. We therefore argue that the reverse ring closing reaction is faster than the forward ring opening reaction and, thus, it establishes an equilibrium between the two and subsequently allows formation of the more stable species <i>via</i> outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.</p>

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