Epoxidation of trans-4-Aminocyclohex-2-en-1-ol Derivatives: Competition of Hydroxy-Directed and Ammonium-Directed Pathways

2015 ◽  
Vol 68 (4) ◽  
pp. 610 ◽  
Author(s):  
Méabh B. Brennan ◽  
Stephen G. Davies ◽  
Ai M. Fletcher ◽  
James A. Lee ◽  
Paul M. Roberts ◽  
...  
Keyword(s):  
Hydroxy Group ◽  
Relative Rate ◽  
Ammonium Ion ◽  
Epoxide Ring ◽  
Hydrogen Bond Donor ◽  
Epoxidation Reaction ◽  
Sterically Demanding ◽  
Tertiary Amino ◽  
Directing Group

N-Substituted trans-4-aminocyclohex-2-en-1-ols undergo epoxidation upon treatment with Cl3CCO2H followed by meta-chloroperbenzoic acid (m-CPBA) via competitive pathways resulting from hydrogen-bonding delivery by both the hydroxy group and the in situ formed ammonium ion. The absence of epoxide ring-opening in these reactions renders these substrates a unique platform for analysing the effect of the two competing directing groups on the rate of the epoxidation reaction: the diastereoisomeric ratio of the epoxide products is also the ratio of the rate constants describing the competing epoxidation processes (the group with the higher directing ability dominating the stereochemical course of the reaction). Analysis of the diastereoisomeric epoxide mixtures obtained from these reactions allowed the following order of directing group ability to be defined: NHBn >> NMeBn > OH > NBn2. The large difference in rate between the secondary and tertiary amino groups is consistent with superior directing ability of the former due to the presence of two hydrogen-bond donor sites on the secondary ammonium ion and/or an increased conformational flexibility to adopt an optimum geometry. The rate of an ammonium-directed epoxidation proceeds ~10 times slower in the presence of an allylic hydroxy group than in its absence, consistent with the presence of the additional, inductively electron-withdrawing heteroatom abating the nucleophilicity of the olefin. The relative rate of the hydroxy-directed epoxidation process in the presence of a more sterically demanding ammonium substituent is greater than that in the presence of a less sterically demanding one: this effect is attributed to an increased bias for the half-chair conformer in which the bulky ammonium substituent and, hence, the hydroxy group occupy pseudo-equatorial sites, thus allowing the latter to direct the reaction more efficiently.

Participation of the oxygen-containing substituent in alkaline saponification of 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestane derivatives

1986 ◽  
Vol 51 (4) ◽  
pp. 930-936 ◽  
Author(s):  
Helena Velgová
Keyword(s):  
Hydroxy Group ◽  
Acetoxy Group ◽  
Epoxide Ring ◽  
Main Component ◽  
Hydroxy Groups

Alkaline saponification of the 3-acetoxy group in 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5βcholestane derivatives I-VI was studied. It was found that the 3α- and 4aα-hydroxy groups participated in the cleavage of the 5β,6β-epoxide ring in the derivatives II-IV: the 5(O)n participation by the 3α-hydroxy group (the derivatives III and IV) led to formation of the transannular 3α,5α-epoxides XII and XIV whereas the participation by the 4aα-hydroxy group (the derivatives II and IV) gave rise to the 4aα,5α-epoxides IX and XV. The 5(O)n participation by the 3α-hydroxy group predominated over the preparation by the 4aα-hydroxy group. In the case of the 4a-keto epoxides V and VI the retroaldol-aldol type isomerization led to formation of 3β-hydroxy-4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestan-4a-one as the main component of the equilibration mixtures.

Synthesis of a sequence-controlled in-chain alkynyl/tertiary amino dual-functionalized terpolymer via living anionic polymerization

2018 ◽  
Vol 9 (1) ◽  
pp. 108-120 ◽  
Author(s):  
Lincan Yang ◽  
Hongwei Ma ◽  
Li Han ◽  
Xinyu Hao ◽  
Pibo Liu ◽  
...  
Keyword(s):  
Anionic Polymerization ◽  
Kinetic Characteristics ◽  
Living Anionic Polymerization ◽  
Sequence Structure ◽  
H Nmr ◽  
Nmr Method ◽  
Tertiary Amino

A dual-functionalized sequence-defined terpolymer was synthesized via living anionic polymerization; meanwhile its kinetic characteristics and sequence structure were investigated in detail via the in situ1H NMR method.

scholarly journals Preparation and Characterization of P(AN-VAc-PMMT) Nanocomposites and Nanofibers

2014 ◽  
Vol 2014 ◽  
pp. 1-4
Author(s):  
Jun Liu ◽  
Yuguo Zhuo ◽  
Qingshan Li ◽  
Wei Hong ◽  
Guangzhong Xing
Keyword(s):  
Emulsion Polymerization ◽  
Quaternary Ammonium ◽  
Ammonium Ion ◽  
Nanofiber Morphology

P(AN-VAc-PMMT) nanocomposites were prepared usingin situemulsion polymerization and further confirmed by FTIR. A polymerizable quaternary ammonium ion monomer was used to modify montmorillonite. XRD testing showed that the quaternary ammonium ion was successfully intercalated into the montmorillonite chip layer. This is the first paper to discuss an investigation of P(AN-VAc-PMMT) nanofiber morphology using SEM. The fibers were prepared through electrospinning.

In-Situ Leaching of South Texas Uranium Ores-Part 2: Oxidative Removal of Adsorbed Ammonium Ions With Sodium Hypochlorite

1983 ◽  
Vol 23 (02) ◽  
pp. 387-396 ◽  
Author(s):  
J.M. Paul ◽  
W.F. Johnson ◽  
A. Fletcher ◽  
P.B. Venuto
Keyword(s):  
Cation Exchange ◽  
Sodium Hypochlorite ◽  
Geographical Area ◽  
Ammonium Bicarbonate ◽  
South Texas ◽  
Ion Concentration ◽  
Ammonium Ion ◽  
Side Reactions ◽  
Ammonium Ions

Abstract This paper reports a laboratory study of the oxidative destruction by sodium hypochlorite (NaOCl) of ammonium ions adsorbed on relatively reduced south Texas uranium ore. Included are an assessment of reaction stoichiometry, determination of some major reaction pathways and side reactions, and identification of several pathways and side reactions, and identification of several intermediates. Adsorbed ammonium ions were completely removed by 0.5 % NaOCl, with the concentration of NH3 in the effluent falling to a very low value after 10 to 15 PV NaOCl oxidant. A small fraction (5 to 10%) of NaOCl was utilized in reacting with NH3. After the NH3 was nearly depleted, mono-, di-, and trichloramines, the expected intermediates in NaOCl oxidation of NH3, were observed. Chloramine decomposition studies showed that all three decomposed completely within 12 days. Since the ore was relatively highly reducing, the major pan of the NaOCl was, not unexpectedly, consumed in side reactions. Substantial quantities of sulfate, reflecting oxidation of sulfide minerals such as pyrite, were formed, large amounts of uranium were leached out, and substantial amounts of calcium and magnesium ions were also produced during the presaturation with NH4HCO3 preceding the oxidation stage. Introduction A leachate that has sometimes been used for in-situ leaching of uranium ores is a solution of ammonium bicarbonate (NH4HCO3) containing an oxidant-usually hydrogen peroxide (H2O2) or oxygen (O2). The ammonium ion (NH4+) introduced into the ore body upon injection of this leachate is exchanged for cations such as calcium (Ca+2 ) and sodium (Na+), which are associated with mineral species in the formation possessing available cation exchange sites. As the indigenous groundwaters reinvade the leached zone, the adsorption process is reversed with NH4+ ions being displaced from process is reversed with NH4+ ions being displaced from the cation exchange sites and returned to the ground-waters. In general, this latter process maintains the ammonia (NH3 (or NH4+ ion) concentration well above the baseline (pre-mining) value in groundwater for extended periods of time in waters produced from wells in or near the mined zone following cessation of leachate injection. Prior to abandonment of an in-situ leach-mining site by the operator, satisfactory restoration of groundwater quality must be demonstrated. Requirements for this demonstration vary with the geographical area. A summary of applicable regulations has been provided by Kasper et al. A review of the state of restoration demonstrations to Sept. 1979 has been given by Tiepel. Most of the in-situ leach operations in south Texas have been conducted in aquifers containing indigenous waters with TDS contents in the 700- to 3,000-ppm range. Ca+ 2, magnesium (Mg+2), and bicarbonate ion (HCO3 ) concentrations are high in these slightly alkaline waters. These equilibrium water compositions indicate that an appreciable fraction of the interlayer ion exchange sites of the smectite clays in the formation are occupied by Ca+2 or Mg+2 ions. SPEJ P. 387

Rhodium-Catalyzed Direct Annulation of Aldehydes with Alkynes Leading to Indenones: Proceeding through in Situ Directing Group Formation and Removal

2013 ◽  
Vol 15 (18) ◽  
pp. 4754-4757 ◽  
Author(s):  
Shuyou Chen ◽  
Jintao Yu ◽  
Yan Jiang ◽  
Fan Chen ◽  
Jiang Cheng
Keyword(s):  
Group Formation ◽  
Directing Group

Rhodium(iii)-catalyzed indole synthesis at room temperature using the transient oxidizing directing group strategy

2019 ◽  
Vol 55 (64) ◽  
pp. 9547-9550 ◽  
Author(s):  
Yaping Shang ◽  
Krishna Jonnada ◽  
Subhash Laxman Yedage ◽  
Hua Tu ◽  
Xiaofeng Zhang ◽  
...  
Keyword(s):  
Room Temperature ◽  
Nitroso Group ◽  
Group Strategy ◽  
Internal Alkynes ◽  
Directing Group ◽  
Catalyzed Reactions ◽  
Indole Synthesis

Rh-Catalyzed reactions of N-alkyl anilines with internal alkynes at room temperature have been developed using an in situ generated N-nitroso group as a transient oxidizing directing group.

scholarly journals Catalytic C(sp3 )−H Arylation of Free Primary Amines with an exo Directing Group Generated In Situ

2016 ◽  
Vol 55 (31) ◽  
pp. 9084-9087 ◽  
Author(s):  
Yan Xu ◽  
Michael C. Young ◽  
Chengpeng Wang ◽  
David M. Magness ◽  
Guangbin Dong
Keyword(s):  
Primary Amines ◽  
Directing Group

Synthesis of Conjugated Trienes and Related Oxidation Products of α-Farnesene

1994 ◽  
Vol 47 (11) ◽  
pp. 1979 ◽  
Author(s):  
MA Brimble ◽  
DD Rowan ◽  
JA Spicer
Keyword(s):  
Ring Opening ◽  
Room Temperature ◽  
Oxidation Products ◽  
Epoxide Ring ◽  
Epoxide Ring Opening ◽  
Superficial Scald ◽  
Conjugated Trienes ◽  
Conjugated Triene ◽  
Cyclic Peroxide

The synthesis of conjugated trienes and related oxidation products of α- farnesene (1), principally from the epoxides of α- farnesene (1), is reported. Base-promoted ring opening of 6,7-epoxide (4) by KOBut/LiNPri2 affords the conjugated triene (2), whilst the 3,4-epoxide (5) affords trienol (7). In contrast, 10,11-epoxide (6) fails to undergo epoxide ring opening; it rearranges to the conjugated triene epoxide (8). Base-promoted ring opening of bisepoxide (9) afforded trienol epoxide (11) at -30°C, whilst cyclization to tetrahydrofurans (10a,b) occurred at room temperature. Photosensitized oxidation of 10,11-epoxide (6) followed by in situ treatment with acid gave the cyclic peroxide (3) and on reduction triol (12). Bisallylic alcohol (13) was prepared by alkylation of 3-methylsulfolene with geranial. Trienes (2) and (3) have been isolated previously as autoxidation products of α- farnesene (1) and are implicated as the causal agents of superficial scald of stored apples.

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