scholarly journals Gold-catalyzed cyclization of allenyl acetal derivatives

2013 ◽  
Vol 9 ◽  
pp. 1751-1756 ◽  
Author(s):  
Dhananjayan Vasu ◽  
Samir Kundlik Pawar ◽  
Rai-Shung Liu
Keyword(s):  
Acetate Group ◽  
Deuterium Labeling ◽  
Allyl Cation ◽  
Hydride Shift

The gold-catalyzed transformation of allenyl acetals into 5-alkylidenecyclopent-2-en-1-ones is described. The outcome of our deuterium labeling experiments supports a 1,4-hydride shift of the resulting allyl cationic intermediates because a complete deuterium transfer is observed. We tested the reaction on various acetal substrates bearing a propargyl acetate, giving 4-methoxy-5-alkylidenecyclopent-2-en-1-ones 4 via a degradation of the acetate group at the allyl cation intermediate.

Deuterium labeling as a test of intramolecular hydride mechanisms in the fragmentation of 2-(1-hydroxybenzyl)-N1′-methylthiamin

2005 ◽  
Vol 83 (9) ◽  
pp. 1277-1280 ◽  
Author(s):  
Glenn Ikeda ◽  
Ronald Kluger
Keyword(s):  
Proton Transfer ◽  
Spectroscopic Analysis ◽  
Hydride Transfer ◽  
Fragmentation Reaction ◽  
Deuterium Labeling ◽  
Benzoylformate Decarboxylase ◽  
Hydride Shift ◽  
Benzoin Condensation ◽  
Normal Water ◽  
Amino Pyrimidine

2-(1-Hydroxybenzyl)-N1′-methylthiamin (1b) is a model for the addition intermediate in the thiamin catalyzed benzoin condensation. However, N-alkylation alters the reactivity of the compound: instead of undergoing base-catalyzed formation of benzaldehyde and N1′-methylthiamin, it rapidly forms trimethyl amino pyrimidine (2b) and phenylthiazole ketone (3). The base-catalyzed fragmentation process is faster than the analogous enzymic reaction (in benzoylformate decarboxylase) under the same conditions. One possible mechanism for the rapid fragmentation is an internal hydride transfer from α-C2 to the methylene bridge between the heterocycles. To test the hydride mechanism we prepared α-C2-deuterated 1b and conducted the fragmentation reaction in normal water. Spectroscopic analysis revealed that the trimethyl aminopyrimidine product does not contain any deuterium, ruling out a hydride transfer mechanism. This supports a mechanism for fragmentation that proceeds instead via a proton transfer from α-C2. Since protonation (and hence, deprotonation) of that site is part of the normal catalytic cycle of benzoylformate decarboxylase, the enzyme must divert the reaction from the lowest energy pathway since it would share a common intermediate with the fragmentation process.Key words: thiamin, fragmentation, benzoylformate decarboxylase, proton transfer, hydride shift.

scholarly journals Esterifications with 2-(Trimethylsilyl)ethyl 2,2,2-Trichloroacetimidate

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 17-25
Author(s):  
Wenhong Lin ◽  
Shea T. Meyer ◽  
Shawn Dormann ◽  
John D. Chisholm
Keyword(s):  
Carboxylic Acid ◽  
High Yield ◽  
Deuterium Labeling ◽  
Ester Formation ◽  
Acid Substrate

2-(Trimethylsilyl)ethyl 2,2,2-trichloroacetimidate is readily synthesized from 2-trimethylsilylethanol in high yield. This imidate is an effective reagent for the formation of 2-trimethylsilylethyl esters without the need for an exogenous promoter or catalyst, as the carboxylic acid substrate is acidic enough to promote ester formation without an additive. A deuterium labeling study indicated that a β-silyl carbocation intermediate is involved in the transformation.

scholarly journals Regioselective activation of benzocyclobutenones and dienamides lead to anti-Bredt bridged-ring systems by a [4+4] cycloaddition

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jianyu Zhang ◽  
Xi Wang ◽  
Tao Xu
Keyword(s):  
Type Ii ◽  
Ring Systems ◽  
Hydride Shift

AbstractTo the best of our knowledge, bridgehead carbon benzofused-bridged ring systems have previously not been accessible to the synthetic community. Here, we describe a formal type-II [4 + 4] cycloaddition approach that provides fully sp2-carbon embedded anti-Bredt bicyclo[5.3.1] skeletons through the Rh-catalyzed C1–C8 activation of benzocyclobutenones (BCBs) and their coupling with pedant dienamides. Variously substituted dienamides have been coupled with BCBs to provide a range of complex bicyclo[5.3.1] scaffolds (>20 examples, up to 89% yield). The bridged rings were further converted to polyfused hydroquinoline-containing tetracycles via a serendipitously discovered transannular 1,5-hydride shift/Prins-like cyclization/Schmidt rearrangement cascade.

scholarly journals FSMP-06. IN VIVO MONITORING OF LDHA EXPRESSION IN GLIOBLASTOMA USING QUANTITATIVE EXCHANGED-LABEL TURNOVER 1H MRS TECHNIQUE

2020 ◽  
Vol 3 (Supplement_1) ◽  
pp. i17-i17
Author(s):  
Puneet Bagga ◽  
Laurie Rich ◽  
Mohammad Haris ◽  
Neil Wilson ◽  
Mitch Schnall ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Lactate Production ◽  
Deuterium Labeling ◽  
1H Mrs ◽  
In Vivo Monitoring ◽  
Lactate Turnover ◽  
Crucial Information ◽  
Specialized Hardware

Abstract Most cancers, including glioblastomas (GBMs), rely extensively on glycolysis to support growth, proliferation, and survival. A hallmark of this elevated glycolysis is overexpression of Lactate dehydrogenase-A (LDHA) protein leading to increased uptake of glucose and overproduction of lactate. Various clinical trials using LDHA as a target for diagnosis and treatment have yielded encouraging results. However, in vivo monitoring of LDHA expression has been challenging due to either requirement of administration of radioactive substrates or specialized hardware. In this presentation, we will demonstrate a new method-quantitative exchanged-label turnover MRS (QELT, or simply qMRS)-that increases the sensitivity of magnetic resonance-based metabolic mapping without the requirement for specialized hardware. qMRS relies on the administration of deuterated (2H-labeled) substrates to track the production of downstream metabolites. Since 2H is invisible on 1H MRS, replacement of 1H with 2H due to metabolic turnover leads to an overall reduction in 1H MRS signal for the corresponding metabolites. We applied our qMRS technique to monitor the rate of lactate production in a preclinical GBM model. Infusion of [6,6’-2H2]glucose led to downstream deuterium labeling of lactate, thereby resulting in a reduction in the 1.33 ppm lactate-CH3 peak on 1H MRS over time. The subtraction of post-administration 1H MR spectra from the pre-infusion spectra aided in the determination of the kinetics of the lactate turnover. We believe that the detection and quantification of lactate production kinetics may provide crucial information regarding tumor LDHA expression non-invasively in GBMs without requiring biopsies. Hence, qMRS is expected to open up new opportunities to probe LDHA expression differences in a variety of gliomas, including GBMs and astrocytomas. This method takes advantage of the universal availability and ease of implementation of 1H MRS on all clinical and preclinical magnetic resonance scanners.

Transition metal acetates

1968 ◽  
Vol 46 (22) ◽  
pp. 3443-3446 ◽  
Author(s):  
D. A. Edwards ◽  
R. N. Hayward
Keyword(s):  
Solid State ◽  
Thermogravimetric Analysis ◽  
Transition Metal ◽  
Infrared Spectra ◽  
Magnetic Moments ◽  
Acetate Group ◽  
Visible Spectra

Some anhydrous transition metal acetates (Mn(II), Co(II), Cu(II), Ni(II), Zn(II), Ag(I), Mo(II), Ce(III), La(III)) have been prepared and their infrared spectra measured in the solid state. The infrared spectra have been related to established modes of bonding of the acetate group to metals. Thermal decompositions of the anhydrous acetates have been investigated by thermogravimetric analysis; magnetic moments and visible spectra have been measured.

A special-salt effect upon the hydride shift during the acetolysis of cyclohexyl tosylate

1976 ◽  
Vol 41 (24) ◽  
pp. 3920-3922 ◽  
Author(s):  
M. Gillard ◽  
F. Metras ◽  
S. Tellier ◽  
J. J. Dannenberg
Keyword(s):  
Salt Effect ◽  
Hydride Shift

scholarly journals Changes in Thermodynamic Interactions at Highly Immiscible Polymer/Polymer Interfaces due to Deuterium Labeling

2006 ◽  
Vol 110 (22) ◽  
pp. 10602-10605 ◽  
Author(s):  
Shane E. Harton ◽  
Frederick A. Stevie ◽  
Zhengmao Zhu ◽  
Harald Ade
Keyword(s):  
Polymer Interfaces ◽  
Deuterium Labeling ◽  
Immiscible Polymer
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