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A p p e a r a n c e
F r o m W i k i p e d i a , t h e f r e e e n c y c l o p e d i a
Oxazole
Names
Preferred IUPAC name
Identifiers
CAS Number
3D model (JSmol )
Beilstein Reference
103851
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.005.474
EC Number
Gmelin Reference
485850
MeSH
D010080
PubChem CID
UNII
CompTox Dashboard (EPA )
InChI=1S/C3H3NO/c1-2-5-3-4-1/h1-3H N
Key: ZCQWOFVYLHDMMC-UHFFFAOYSA-N N
InChI=1/C3H3NO/c1-2-5-3-4-1/h1-3H
Key: ZCQWOFVYLHDMMC-UHFFFAOYAD
Properties
Chemical formula
C 3 H 3 N O
Molar mass
69.06 g/mol
Density
1.050 g/cm3
Boiling point
69.5 °C (157.1 °F; 342.6 K )
Acidity (p K a 0.8 (of conjugate acid)[2]
Hazards
GHS labelling[3]
Pictograms
Signal word
Danger
Hazard statements
H225 , H318
Precautionary statements
P210 , P233 , P240 , P241 , P242 , P243 , P264+P265 , P280 , P303+P361+P353 , P305+P354+P338 , P317 , P370+P378 , P403+P235 , P501
Supplementary data page
Oxazole (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
Chemical compound
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.[4] aromatic compounds but less so than the thiazoles. Oxazole is a weak base; its conjugate acid has a p K a imidazole .
Preparation [ edit ]
The classic synthetic route the Robinson–Gabriel synthesis by dehydration of 2-acylaminoketones:
The Robinson–Gabriel synthesis
The Fischer oxazole synthesis from cyanohydrins and aldehydes is also widely used:
Fischer Oxazole Synthesis
Other methods are known including the reaction of α-haloketones and formamide and the Van Leusen reaction with aldehydes and TosMIC .
Biosynthesis [ edit ]
In biomolecules , oxazoles result from the cyclization and oxidation of serine or threonine nonribosomal peptides :[5]
Where X = H, CH 3 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 ]
With a pKa pK a Deprotonation of oxazoles occurs at C2. Formylation with dimethylformamide gives 2-formyloxazole. The lithio compound exists in equilibrium with the ring-opened enolate-isonitrile , which can be trapped by silylation .[4]
Electrophilic aromatic substitution takes place at C5, but requiring electron donating groups .
Nucleophilic aromatic substitution takes place with leaving groups at C2.
Diels–Alder reactions involving oxazole (as dienes) and electrophilic alkenes has been well developed as a route to pyridines . In this way, alkoxy-substituted oxazoles serve a precursors to the pyridoxyl system, as found in vitamin B6 . The initial cycloaddition affords a bicyclic intermediate, with an acid-sensitive oxo bridgehead.
Use of an oxazole in the synthesis of a precursor to pyridoxine , which is converted to vitamin B6 .[6]
Cornforth rearrangement of 4-acyloxazoles is a thermal rearrangement reaction with the organic acyl residue and the C5 substituent changing positions.
Various oxidation reactions. One study[7] CAN to the corresponding imide and benzoic acid :
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 ]
Additional reading [ edit ]
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. doi :10.1021/ol061975c
References [ edit ]
^ Zoltewicz, J. A. & Deady, L. W. Quaternization of heteroaromatic compounds. Quantitative aspects. Adv. Heterocycl. Chem. 22, 71-121 (1978).
^ "Oxazole" . pubchem.ncbi.nlm.nih.gov .
^ a b T. L. Gilchrist (1997). Heterocyclic Chemistry (3 ed.). Longman. ISBN 0-582-01421-2
^ Roy, Ranabir Sinha; Gehring, Amy M.; Milne, Jill C.; Belshaw, Peter J.; Walsh, Christopher T.; Roy, Ranabir Sinha; Gehring, Amy M.; Milne, Jill C.; Belshaw, Peter J.; Walsh, Christopher T. (1999). "Thiazole and Oxazole Peptides: Biosynthesis and Molecular Machinery". Natural Product Reports . 16 2 ): 249–263. doi :10.1039/A806930A . PMID 10331285 .
^ Gérard Moine; Hans-Peter Hohmann; Roland Kurth; Joachim Paust; Wolfgang Hähnlein; Horst Pauling; Bernd–Jürgen Weimann; Bruno Kaesler (2011). "Vitamins, 6. B Vitamins". Ullmann's Encyclopedia of Industrial Chemistry doi :10.1002/14356007.o27_o09 . ISBN 978-3-527-30673-2
^ "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
R e t r i e v e d f r o m " https://en.wikipedia.org/w/index.php?title=Oxazole&oldid=1182672747 " C a t e g o r i e s : ● O x a z o l e s ● S i m p l e a r o m a t i c r i n g s H i d d e n c a t e g o r i e s : ● A r t i c l e s w i t h o u t K E G G s o u r c e ● E C H A I n f o C a r d I D f r o m W i k i d a t a ● A r t i c l e s w i t h c h a n g e d I n C h I i d e n t i f i e r ● C h e m b o x h a v i n g G H S d a t a ● C h e m i c a l a r t i c l e s h a v i n g a d a t a p a g e ● A r t i c l e s c o n t a i n i n g u n v e r i f i e d c h e m i c a l i n f o b o x e s ● C h e m b o x i m a g e s i z e s e t ● A r t i c l e s w i t h s h o r t d e s c r i p t i o n ● S h o r t d e s c r i p t i o n m a t c h e s W i k i d a t a
● T h i s p a g e w a s l a s t e d i t e d o n 3 0 O c t o b e r 2 0 2 3 , a t 1 8 : 0 4 ( U T C ) . ● T e x t i s a v a i l a b l e u n d e r t h e C r e a t i v e C o m m o n s A t t r i b u t i o n - S h a r e A l i k e L i c e n s e 4 . 0 ;
a d d i t i o n a l t e r m s m a y a p p l y . B y u s i n g t h i s s i t e , y o u a g r e e t o t h e T e r m s o f U s e a n d P r i v a c y P o l i c y . W i k i p e d i a ® i s a r e g i s t e r e d t r a d e m a r k o f t h e W i k i m e d i a F o u n d a t i o n , I n c . , a n o n - p r o f i t o r g a n i z a t i o n . ● P r i v a c y p o l i c y ● A b o u t W i k i p e d i a ● D i s c l a i m e r s ● C o n t a c t W i k i p e d i a ● C o d e o f C o n d u c t ● D e v e l o p e r s ● S t a t i s t i c s ● C o o k i e s t a t e m e n t ● M o b i l e v i e w
