scholarly journals Catalyst-free regioselective acetylation of primary hydroxy groups in partially protected and unprotected thioglycosides with acetic acid

RSC Advances ◽  
2020 ◽  
Vol 10 (60) ◽  
pp. 36836-36842
Author(s):  
Polina I. Abronina ◽  
Nelly N. Malysheva ◽  
Alexander I. Zinin ◽  
Natalya G. Kolotyrkina ◽  
Elena V. Stepanova ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Elevated Temperatures ◽  
Catalyst Free ◽  
Protective Groups ◽  
Hydroxy Groups ◽  
Anhydrous Acetic Acid

Highly regioselective acetylation of primary hydroxy groups in thioglycoside derivatives was achieved by treatment with aqueous or anhydrous acetic acid (60–100%) at elevated temperatures (80–118 °C), avoiding manipulations with protective groups.

scholarly journals Abraham model correlations for estimating solute transfer of neutral molecules into anhydrous acetic acid from water and from the gas phase

2015 ◽  
Vol 212 ◽  
pp. 16-22 ◽  
Author(s):  
Dawn M. Stovall ◽  
Amber Schmidt ◽  
Colleen Dai ◽  
Shoshana Zhang ◽  
William E. Acree ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Gas Phase ◽  
Solute Transfer ◽  
Abraham Model ◽  
Anhydrous Acetic Acid

Anodic oxidation of halides in anhydrous acetic acid

1973 ◽  
Vol 44 (1) ◽  
pp. 37-45 ◽  
Author(s):  
M. Mastragostino ◽  
G. Casalbore ◽  
S. Valcher
Keyword(s):  
Acetic Acid ◽  
Anodic Oxidation ◽  
Anhydrous Acetic Acid

Light Directs Monomer Coordination in Catalyst-Free Grignard Photopolymerization

2021 ◽  
Author(s):  
Eliot Woods ◽  
Alexandra Berl ◽  
Leanna Kantt ◽  
Michael Wasielewski ◽  
Brandon E. Haines ◽  
...  
Keyword(s):  
Conjugated Polymers ◽  
Radical Anion ◽  
Elevated Temperatures ◽  
Spectroscopic Studies ◽  
Computational Investigation ◽  
Catalyst Free ◽  
Active Layers ◽  
End Groups ◽  
Type Coupling

π-Conjugated polymers can serve as active layers in flexible and lightweight electronics, and are conventionally synthesized by transition-metal-mediated polycondensation at elevated temperatures. We recently reported a photopolymerization of electron-deficient heteroaryl Grignard monomers that enables the catalyst-free synthesis of n-type π-conjugated polymers. Herein we provide an experimental and computational investigation of the mechanism of this photopolymerization. Spectroscopic studies performed <i>in situ</i> and after quenching reveal that the propagating species is a radical anion with halide end groups. DFT calculations for model oligomers suggest a Mg-templated S<sub>RN</sub>1-type coupling, in which Grignard monomer coordination to the radical anion chain avoids the formation of free sp<sup>2</sup> radicals and enables C–C bond formation with very low barriers. We find that light plays an unusual role in the reaction, photoexciting the radical anion chain to shift electron density to the termini and thus favor productive monomer binding.

N-Methylamino Acids in Peptide Synthesis. III. Racemization during Deprotection by Saponification and Acidolysis

1973 ◽  
Vol 51 (15) ◽  
pp. 2555-2561 ◽  
Author(s):  
John R. McDermott ◽  
N. Leo Benoiton
Keyword(s):  
Acetic Acid ◽  
Sodium Hydroxide ◽  
Hydrogen Bromide ◽  
Aqueous Sodium Hydroxide ◽  
Acid Strength ◽  
Carboxyl Group ◽  
Aqueous Sodium ◽  
Aqueous Acid ◽  
Amino Acid Analyzer ◽  
Anhydrous Acetic Acid

The racemization of N-methylamino-acid derivatives in aqueous sodium hydroxide and hydrogen bromide in anhydrous acetic acid and other solvents has been investigated by determining the products of the reaction with an amino-acid analyzer after deprotection. Whereas MeIle-OMe, Z-MeIle, and the N-unmethylated derivatives were only slightly racemized ( <2%), Z-MeIle-OMe (18–24%), Z-Ala-MeLeu-OMe (22%), and Z-Ala-MeLeu-OBu′ (7%) were appreciably racemized by aqueous sodium hydroxide. It is suggested that these derivatives racemize because of the absence of an > N—H or carboxyl group whose ionization would suppress ionization of the neighboring α-C—H bond. Z-Melle and Z-Ala-MeLeu were substantially racemized (68% in 4 h and 34% in 1 h, respectively) by 5.6 N hydrogen bromide in acetic acid. The extent of racemization by acid varied with acid strength, polarity of solvent, and time. Incorporation of label into both isomers of Ala-MeLeu from a solution of the tritiated reagent established that ionization at the α-C—H bond had occurred. No racemization was caused by aqueous acid or by hydrogen chloride.

Screened indicators in anhydrous acetic acid medium: Chromatic evaluation of their transitions

1991 ◽  
Vol 105 (1-3) ◽  
pp. 89-99 ◽  
Author(s):  
Jos� Barbosa ◽  
Elisabeth Bosch ◽  
Jos� Luis Cortina ◽  
Mart� Ros�s
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
Acetic Acid Medium ◽  
Screened Indicators ◽  
Anhydrous Acetic Acid
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