Oxazole

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Oxazole
Full structural formula
Skeletal formula with numbers
Ball-and-stick model
Space-filling model
Names
IUPAC name
1,3-oxazole
Identifiers
288-42-6 N
ChEBI CHEBI:35597 N
ChemSpider 8898 N
EC Number 206-020-8
Jmol interactive 3D Image
MeSH D010080
PubChem 9255
Properties
C3H3NO
Molar mass 69.06 g/mol
Density 1.050 g/cm3
Boiling point 69 to 70 °C (156 to 158 °F; 342 to 343 K)
Acidity (pKa) 0.8 (of conjugate acid) [1]
Supplementary data page
Refractive index (n),
Dielectric constantr), etc.
Thermodynamic
data
Phase behaviour
solid–liquid–gas
UV, IR, NMR, MS
N verify (what is YesYN ?)
Infobox references

Oxazole is the parent compound for a vast class of heterocyclic aromatic organic compounds. These are azoles with an oxygen and a nitrogen separated by one carbon.[2] Oxazoles are aromatic compounds but less so than the thiazoles. Oxazole is a weak base; its conjugate acid has a pKa of 0.8, compared to 7 for imidazole.

Preparation[edit]

Classical oxazole synthetic methods in organic chemistry are

Other methods are reported in literature.

oxazoline from propargyl amides Merkul 2006
Oxazoline Synthesis Continuous Reactor

Biosynthesis[edit]

In biomolecules, oxazoles result from the cyclization and oxidation of serine or threonine nonribosomal peptides:

Where X = H, CH
3
for serine and threonine respectively, B = base.
(1) Enzymatic cyclization. (2) Elimination. (3) [O] = enzymatic oxidation.

Oxazoles are not as abundant in biomolecules as the related thiazoles with oxygen replaced by a sulfur atom.

Reactions[edit]

Oxazoline CAN oxidation
In the balanced half-reaction three equivalents of water are consumed for each equivalent of oxazoline, generating 4 protons and 4 electrons (the latter derived from CeIV).

See also[edit]

References[edit]

  1. ^ Zoltewicz, J. A. & Deady, L. W. Quaternization of heteroaromatic compounds. Quantitative aspects. Adv. Heterocycl. Chem. 22, 71-121 (1978).
  2. ^ Heterocyclic Chemistry TL Gilchrist, The Bath press 1985 ISBN 0-582-01421-2
  3. ^ A new consecutive three-component oxazole synthesis by an amidation–coupling–cycloisomerization (ACCI) sequence Eugen Merkul and Thomas J. J. Müller Chem. Commun., 2006, 4817 - 4819, doi:10.1039/b610839c
  4. ^ Fully Automated Continuous Flow Synthesis of 4,5-Disubstituted Oxazoles Marcus Baumann, Ian R. Baxendale, Steven V. Ley, Christoper D. Smith, and Geoffrey K. Tranmer Org. Lett.; 2006; 8(23) pp 5231 - 5234; (Letter) doi:10.1021/ol061975c
  5. ^ They react together in the first phase in a continuous flow reactor to the intermediate enol and then in the second phase in a phosphazene base (PS-BEMP) induced cyclization by solid-phase synthesis.
  6. ^ Ceric Ammonium Nitrate Promoted Oxidation of Oxazoles David A. Evans, Pavel Nagorny, and Risheng Xu Org. Lett.; 2006; 8(24) pp 5669 - 5671; (Letter) doi:10.1021/ol0624530