skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Synthesis of a mononuclear magnesium bis(alkoxide) complex and its reactivity in the ring-opening copolymerization of cyclic anhydrides with epoxides
Title: Synthesis of a mononuclear magnesium bis(alkoxide) complex and its reactivity in the ring-opening copolymerization of cyclic anhydrides with epoxides
Synthesis of a new mononuclear magnesium complex with a bulky bis(alkoxide) ligand environment and its reactivity in ring-opening polymerization (ROP) and ring-opening copolymerization (ROCOP) are reported. Reaction of n -butyl- sec -butylmagnesium with two equivalents of HOR (HOR = di- tert -butylphenylmethanol, HOC t Bu 2 Ph) formed Mg(OR) 2 (THF) 2 . The reaction proceeded via the Mg(OR)( sec -Bu)(THF) 2 intermediate that was independently synthesized by treating n -butyl- sec -butylmagnesium with one equivalent of HOR. Mg(OR) 2 (THF) 2 led to active albeit not well-controlled ROP of rac -lactide. In contrast, well-controlled ROCOP of epoxides with cyclic anhydrides was observed, including efficient and alternating copolymerization of phthalic anhydride with cyclohexene oxide as well as rare copolymerization of phthalic anhydride with limonene oxide and terpolymerization of phthalic anhydride with both cyclohexene oxide and limonene oxide. In addition, novel copolymerization of dihydrocoumarin with limonene oxide is described.  more » « less
Award ID(s):
1855681
PAR ID:
10143071
Author(s) / Creator(s):
; ; ; ; ; ;
Date Published:
Journal Name:
Dalton Transactions
Volume:
49
Issue:
8
ISSN:
1477-9226
Page Range / eLocation ID:
2715 to 2723
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; (, Dalton Transactions)
    null (Ed.)
    Reaction of LiOC t Bu 2 Ph with TlPF 6 forms the dimeric Tl 2 (OC t Bu 2 Ph) 2 complex, a rare example of a homoleptic thallium alkoxide complex demonstrating formally two-coordinate metal centers. Characterization of Tl 2 (OC t Bu 2 Ph) 2 by 1 H and 13 C NMR spectroscopy and X-ray crystallography reveals the presence of two isomers differing by the mutual conformation of the alkoxide ligands, and by the planarity of the central Tl–O–Tl–O plane. Tl 2 (OC t Bu 2 Ph) 2 serves as a convenient precursor to the formation of old and new [M(OC t Bu 2 Ph) n ] complexes (M = Cr, Fe, Cu, Zn), including a rare example of T-shaped Zn(OC t Bu 2 Ph) 2 (THF) complex, which could not be previously synthesized using more conventional LiOR/HOR precursors. The reaction of [Ru(cymene)Cl 2 ] 2 with Tl 2 (OC t Bu 2 Ph) 2 results in the formation of a ruthenium( ii ) alkoxide complex. For ruthenium, the initial coordination of the alkoxide triggers C–H activation at the ortho -H of [OC t Bu 2 Ph] which results in its bidentate coordination. In addition to Tl 2 (OC t Bu 2 Ph) 2 , related Tl 2 (OC t Bu 2 (3,5-Me 2 C 6 H 3 )) 2 was also synthesized, characterized, and shown to exhibit similar reactivity with iron and ruthenium precursors. Synthetic, structural, and spectroscopic characterizations are presented. 
    more » « less
  2. ; ; ; ; ; ; ; (, Chemical Communications)
    null (Ed.)
    Pentacoordinate Al catalysts comprising bipyridine (bpy) and phenanthroline (phen) backbones were synthesized and their catalytic activity in epoxide/anhydride copolymerization was investigated and compared to ( t-Bu salph)AlCl. Stoichiometric reactions of tricyclic anhydrides with Al alkoxide complexes produced ring-opened products that were characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography, revealing key regio- and stereochemical aspects. 
    more » « less
  3. ; ; ; ; ; (, Organic Letters)
    The ring-opening of cyclic ethers (epoxide, oxetane, THF, and THP) by carboxylic acids was achieved by using N-iodosuccinimide (NIS) or N-bromosuccinimide (NBS) and triphenylphosphine under the irradiation of blue light. The corresponding omega-haloalkyl carboxylates were obtained under mild reaction conditions. The reaction is believed to work through a halogen bond complex between NIS (or NBS) and triphenylphosphine, which, upon irradiation with blue light, produces the key phosphine radical cation intermediate that initiates the ring-opening reactions. 
    more » « less
  4. ; ; ; ; ; ; ; ; ; ; et al (, Anesthesiology)
    Background.Safe sensory-selective local anesthetics would be a major advance in the management of acute and chronic pain. Here we describe the sensory-selective local anesthetic properties and the toxicity profile of a known metabolite of amino-amide local anesthetics,2',6'-pipecolylxylidine (PPX). Methods.PPX was synthesized and made into its hydrochloride salt. PPX or ropivacaine (ROP) were injected at the sciatic nerve or intrathecally in rats, who then underwent modified hotplate (sensory) testing and weight-bearing (motor) testing. Rats injected with PPX or ROP were assessed for clinical toxicity endpoints. Conduction blockade was studied with single-unit recordings in mice. Biocompatibility was assessed histologically. Results.In male rats, sciatic sensory and motor block from 15 mM ROP lasted ~150 min; sensory nerve block from 30 mM PPX lasted 67.4 ± 17.4 min without motor block. Addition of chemical permeation enhancers to 30 mM PPX abolished sensory selectivity. Intrathecal 15 mM ROP produced sensory and motor block lasting ~15 min; sensory block from 30 mM PPX lasted 24.8 ± 8.7 min without motor block; repeated injection caused continuous sensory-selective block. In female rats, sciatic nerve blocks with ROP were similar to blocks in males, while blocks with PPX were sensory-selective but higher PPX concentrations were required. Ex vivo, 1.5 mM ROP caused reversible block of Aδ and C-fibers; 15 mM PPX blocked Aδ- but not C-fibers. Systemic 39.0 ± 1.8 mg/kg ROP caused severe clinical toxicity; 75.3 ± 3.2 mg/kg PPX caused none. Tissue reaction to PPX was benign, comparable to that of ROP. Conclusions.PPX provides sensory-selective local and neuraxial anesthesia with a good safety profile. The sensory selectivity may be attributable to the particular hydrophilic-hydrophobic balance of PPX. 
    more » « less
  5. ; ; (, Organic & Biomolecular Chemistry)
    Treatment of isoxazoles with enamines leads to an inverse electron-demand hetero-Diels–Alder reaction that produces substituted pyridines in the presence of TiCl 4 (THF) 2 and titanium powder. The reaction is highly regioselective with only a single isomer of the product observed by GC/MS and tolerant of many common functional groups. The transformation was examined computationally, and it was found that TiCl 4 (or a similar Lewis acid) likely acts to catalyze the reaction. After the initial [4 + 2]-cycloaddition, the oxaza-[2.2.1]-bicycle produced likely ring opens before amine loss to give an N -oxide. The pyridine is then obtained after reduction with TiCl 4 and titanium powder. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email