An oxazolidine is a five-membered ring compound consisting of three

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...

atoms, a

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

atom and an

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

atom. The O atom and NH group are the 1 and 3 positions, respectively. In oxazolidine derivatives, there is always a carbon atom between the O and N atoms (or it would be an ''isoxazolidine''). All of the carbon atoms in oxazolidines are reduced (compare to

oxazole 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. Oxazoles are aromatic compounds but less so than the thiazoles. Oxazole is a weak ...

and

oxazoline Oxazoline is a five-membered heterocyclic organic compound with the formula . It is the parent of a family of compounds called oxazolines (emphasis on plural), which contain non-hydrogenic substituents on carbon and/or nitrogen. Oxazolines are the ...

). Some of their derivatives, the

oxazolidinediones 2,4-Oxazolidinedione is an organic compound with the formula HN(CO)2OCH2. It is a white solid. The parent ring is not particularly important, but this core structure is found in a variety anticonvulsant drugs. The parent compound is obtained by ...

, are used as

anticonvulsant Anticonvulsants (also known as antiepileptic drugs or recently as antiseizure drugs) are a diverse group of pharmacological agents used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of b ...

s. Oxazolidines were first synthesized over 100 years ago.

Monooxazolidines

Oxazolidines that are the precursor to bisoxazolidines are in effect mono-oxazolidines. They are also used as moisture scavengers in polyurethane and other systems.

Dioxooxazolidines

Oxazolidines where the carbon centers at the 1 and 3 positions are

carbonyl In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containing a ...

s are called dioxooxazolidines. Some of these are commercial

fungicide Fungicides are biocidal chemical compounds or biological organisms used to kill parasitic fungi or their spores. A fungistatic inhibits their growth. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality, ...

s including chlozolinate,

vinclozolin Vinclozolin (trade names Ronilan, Curalan, Vorlan, Touche) is a common Dicarboximide fungicides, dicarboximide fungicide used to control diseases, such as blights, rots and molds in vineyards, and on fruits and vegetables such as raspberries, let ...

, and

famoxadone Famoxadone is a fungicide to protect agricultural products against various fungal diseases on fruiting vegetables, tomatoes, potatoes, curcurbits, lettuce and grapes.

Bisoxazolidines

Bisoxazolidines are chemical compounds that contain two oxazolidine rings. They are used as performance modifiers in

polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic chemistry, organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethan ...

coatings and paints. The rings

hydrolyze Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolysis ...

in the presence of moisture to give

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ...

and

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...

groups, which can then react with

diisocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

s, polyisocyanates and polyurethane prepolymers to form a coating. The amine groups will form urea linkages and the hydroxyl group will form urethane links. The use of a bisoxazolidine in a polyurethane system can prevent the unwanted reaction between isocyanate and moisture resulting in coating defects, as a result of carbon dioxide release. This moisture-triggered curing route is preferential to moisture cure. As the ring opening reaction is

catalyzed Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

by acids, usually

organic acid An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are rel ...

s or anhydrides of carboxylic acids are added in a small amount. The choice of linker between the two oxazolidine rings has a large impact on the performance when used to cure isocyanates. A rigid linker group increases a polyurethanes toughness. A flexible linker group imparts flexibility and increases elongation of a coating. These differences are the reason why bisoxazolidines are used to enhance the performance of polyurethane systems. Usually the rings are linked by esters, urethanes, carbonate or have the two rings fused together. A key intermediate in manufacturing bisoxazolidines is 2- -(propan-2-yl)-1,3-oxazolidin-3-ylthanol. The hydroxy group on the molecule allows for further reaction with

hexamethylene diisocyanate Hexamethylene diisocyanate (HDI) is the organic compound with the formula (CH2)6(NCO)2. It is classified as an diisocyanate. It is a colorless liquid. It has sometimes been called HMDI but this not usually done to avoid confusion with Hydrogenated ...

for example.

Isoxazolidines

In an isoxazolidine nitrogen and oxygen occupy adjacent positions (1 and 2) in the ring: this is the saturated analogue of

Isoxazole Isoxazole is an electron-rich azole with an oxygen atom next to the nitrogen. It is also the class of compounds containing this ring. Isoxazolyl is the univalent radical derived from isoxazole. Occurrence Isoxazole rings are found in some natural ...

. Isoxazolidines can be produced by the

nitrone-olefin (3+2) cycloaddition The nitrone-olefin (3+2) cycloaddition reaction is the combination of a nitrone with an alkene or alkyne to generate an isoxazoline or isoxazolidine via a +2cycloaddition process. This reaction is a 1,3-dipolar cycloaddition, in which the nitrone ...

reaction.

References

{{reflist

Monooxazolidines

Dioxooxazolidines

Bisoxazolidines

Isoxazolidines

See also

References