- ONE-STEP SYNTHESIS OF OXAZOLES FROM KETONES AND NITRILES USING COPPER(II) TRIFLUOROMETHANESULFONATE AS A KEY REAGENT
-
Oxazoles were prepared in one step from ketones and nitriles using copper(II) trifluoromethanesulfonate under acid catalysis.
- Nagayoshi, Kazuo,Sato, Tadashi
-
-
Read Online
- Heterocyclic volatiles formed by heating cysteine or hydrogen sulfide with 4-hydroxy-5-methyl-3(2H)-furanone at pH 6.5
-
The reaction of 4-hydroxy-5-methyl-3(2H)-furanone (HMF) with cysteine or hydrogen sulfide at pH 6.5 for 60 min at 140°C produced complex mixtures of volatile compounds, the majority of these containing either sulfur or nitrogen. Of the 68 compounds detect
- Whitfield, Frank B.,Mottram, Donald S.
-
p. 816 - 822
(2007/10/03)
-
- Mechanistic Studies of 2-(1-Hydroxyethyl)-2,4,5-trimethyl-3-oxazoline Formation under Low Temperature in 3-Hydroxy-2-butanone/Ammonium Acetate Model Systems
-
Volatile compounds formed from the reaction of 3-hydroxy-2-butanone/ammonium acetate at 25, 55 and 85 °C were investigated. Six compounds were characterized by gas chromatography - mass spectrometry (EI and CI). Among the volatile compounds identified, an interesting intermediate compound, 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline, was found. 15N-Labeled ammonium acetate was used to confirm the structure of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline. The formation pathway of these volatile compounds was proposed. In these model systems, 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline was formed at the reaction temperature below 25 °C. On the other hand, tetramethylpyrazine was the major component when the reaction temperature was higher than 85 °C. The amounts of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline and tetramethylpyrazine increased linearly with the increasing heating time at 55 °C. Protic solvents did not promote 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline formation but did favor the formation of tetramethylpyrazine. A kinetic study of 2-(1-hydroxyethyl)-2,4,5-trimethyl-3-oxazoline formation was also performed, and the activation energy was found to be 16.5 kcal/mol.
- Fu, Hui-Yin,Ho, Chi-Tang
-
p. 1878 - 1882
(2007/10/03)
-
- Reactivity of Heterocyclic Nitrogen Donors in Systems containing the Tetrachloroaurate(III) Anion
-
A series of gold(III) complexes of the type has been prepared and characterized (L = oxazole, benzoxazole, thiazole, their benzo and methyl-substituted derivatives, or 2-methylbenzoselenazole).The five-membered N.O-, N,S- and N,Se-heterocyclic bases are all bound to Au(III) through nitrogen.The kinetics of the displacement of L by chloride to give (1-) has been studied in methanol-water (95:5. v/v) at 25.0 deg C and I = 0.20 mol dm-3 (LiClO4).The equilibrium constants for the reversible processes have also been determined.The reactions of the corresponding pyridine, 4-chloro-, 4-cyano- and 2,6-bis(chloromethyl)-pyridine complexes have also been reexamined under the same conditions.The equlibrium constants, K2, depend upon the basicity of the nitrogen in the ligands and points for all ligands, irrespective of ring size and composition, lie roughly on the same log K2 versus pKa curve.There is no significant systematic steric effect on the equilibrium constants of the sort found for the more basic methyl pyridines.The complexes of the five-membered heterocyclic ligands are approximately ten times less reactive than those of the six-membered N-heterocycles of comparable basicity and exhibit steric retardation from ortho-methyl substituents.The nucleophilicities of these ligands have been calculated and five-membered N,O- and N,S-heterocycles are considerably less reactive than six-membered N-heterocycles of similar basicity.
- Canovese, Luciano,Cattalini, Lucio,Tomaselli, Michele,Tobe, Martin L.
-
p. 307 - 314
(2007/10/02)
-
- Oxazoles from β-acyloxy-N,N-bis(trimethylsilyl)enamines
-
Sequential addition of methyllithium and acyl chlorides to O-trimethylsilyl acetyltrimethylsilane cyanohydrin affords β-acyloxy-N,N-bis(trimethylsilyl)enamines which cyclize to 2-substituted-4,5-dimethyloxazoles under thermolysis or trimethylsilyl trifluoromethanesulfonate treatment.
- Cunico,Kuan
-
p. 1945 - 1948
(2007/10/02)
-
- Base-Catalyzed Cyclization of N-Propargylamides to Oxazoles
-
The base-catalyzed cyclization of some N-propargylamides to oxazoles has been studied in the presence of sodium hydride and potassium carbonate.The α-arylsubstituted propargylamides 1c-d (Ar = p-OMeC6H4 (1c), C6H5 (1d), and p-O2NC6H4 (1e)) cyclized with markedly higher rates (1e > 1d > 1c) than the unsubstituted and α-methyl substituted propargylamides 1a and 1b.A 1H nmr spectroscopic experiment demonstrated the presence of an allenic intermediate in the potassium carbonate-catalyzed ring closure of 1e.The observed rank order of reactivities correlates well withthe acidities of the respective propargylic hydrogens of the amides and with the ability of the ring closed intermediates to stabilize an oxazole anion.The results demonstrate that the base-catalyzed formation of oxazoles from propargylamides may proceed via an allenic intermediate.
- Nilsson, Bjoern M.,Hacksell, Uli
-
p. 269 - 275
(2007/10/02)
-
- A Convenient Synthesis of 2,4,5-Trisubstituted Oxazoles
-
Various 2,4,5-trisubstituted oxazoles (2) have been prepared from the ketoximes (1) in a single step, bei treating the latter with acid chlorides at 80-135 deg C for 8-36 hr.
- Reddy, Gaddam Subba,Bhatt, M. Vivekananda
-
p. 322 - 323
(2007/10/02)
-
- A NEW SYNTHESIS OF OXAZOLES
-
Oxazoles are prepared from the ketoximes in a single pot sequence.
- Bhatt, M. Vivekananda,Reddy, Gaddam Subba
-
p. 2359 - 2360
(2007/10/02)
-
