Oxazole


Oxazole
Oxazole
Identifiers
CAS number 288-42-6 YesY
PubChem 9255
Jmol-3D images Image 1
Properties
Molecular formula C3H3NO
Molar mass 69.06 g mol−1
Density 1.050 g/cm3
Boiling point

69-70 °C

Basicity (pKb) 0.8
Supplementary data page
Structure and
properties
n, εr, etc.
Thermodynamic
data
Phase behaviour
Solid, liquid, gas
Spectral data UV, IR, NMR, MS
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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.[1] 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.

Contents

Preparation

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

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

Where X = H, CH3 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

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

  • Isoxazole, an analog with the nitrogen atom in position 2.
  • Imidazole, an analog with the oxygen replaced by a nitrogen.
  • Thiazole, an analog with the oxygen replaced by a sulfur.
  • Benzoxazole, where the oxazole is fused to another aromatic ring.
  • Pyrrole, an analog without the oxygen atom.
  • Furan, an analog without the nitrogen atom.
  • Oxazoline, which has one double bond reduced.
  • Oxazolidine, which has both double bonds reduced.
  • Oxadiazoles with two nitrogens instead of one (e.g. furazan).

References

  1. ^ Heterocyclic Chemistry TL Gilchrist, The Bath press 1985 ISBN 0-582-01421-2
  2. ^ 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
  3. ^ 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
  4. ^ 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.
  5. ^ 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

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Look at other dictionaries:

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  • oxazole — ˈäksəˌzōl noun Etymology: International Scientific Vocabulary ox (I) + azole 1. : a parent compound C3H3NO containing a ring composed of three carbon atoms, one oxygen atom, and one nitrogen atom with one carbon atom between the oxygen and… …   Useful english dictionary

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  • Oxazole — Ox|azole   [Kurzwort], Singular Oxazol das, s, fünfgliedrige heterozyklische Verbindungen, die im Ring je ein Sauerstoff und ein Stickstoffatom enthalten; nach der Stellung der Heteroatome unterscheidet man Oxazol und Isoxazol …   Universal-Lexikon

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