Regioselective Synthesis ofN-β-Hydroxyethylaziridines by the Ring-Opening Reaction of Epoxides with Aziridine Generated in Situ

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.

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

International Journal of Molecular Sciences ◽

10.3390/ijms20092121 ◽

2019 ◽

Vol 20 (9) ◽

pp. 2121 ◽

Cited By ~ 2

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.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.337.184 ◽

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.

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

Organic & Biomolecular Chemistry ◽

10.1039/d1ob01755a ◽

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...

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

Australian Journal of Chemistry ◽

10.1071/ch11213 ◽

2011 ◽

Vol 64 (8) ◽

pp. 1100 ◽

Cited By ~ 8

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.

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

Journal of Membrane Science ◽

10.1016/j.memsci.2019.03.082 ◽

2019 ◽

Vol 581 ◽

pp. 373-382 ◽

Cited By ~ 10

Author(s):

Haifeng Ji ◽

Hao Xu ◽

Lunqiang Jin ◽

Xin Song ◽

Chao He ◽

...

Keyword(s):

Ring Opening ◽

Surface Engineering ◽

Ring Opening Reaction

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

European Polymer Journal ◽

10.1016/s0014-3057(03)00061-2 ◽

2003 ◽

Vol 39 (8) ◽

pp. 1735-1739 ◽

Cited By ~ 19

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

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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

10.26434/chemrxiv.7094003.v1 ◽

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

The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by pC1C2→s*C3C4 and sC3C4→p*CO interactions in the transition state in a 4-electron process as opposed to only sC3C4→p*CO 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 via outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.

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