Oxetane, or 1,3-propylene oxide, is a heterocyclic organic compound with the molecular formula C
₃H
₆O, having a four-membered ring with three carbon atoms and one oxygen atom.

The term "an oxetane" or "oxetanes" refer to any organic compound containing the oxetane ring.

A typical well-known method of preparation is the reaction of potassium hydroxide with 3-chloropropyl acetate at 150 °C:^[2]

Yield of oxetane made this way is c. 40%, as the synthesis can lead to a variety of by-products including water, potassium chloride, and potassium acetate.

Another possible reaction to form an oxetane ring is the Paternò–Büchi reaction. The oxetane ring can also be formed through diol cyclization^[3] as well as through decarboxylation of a six-membered cyclic carbonate.^{[citation needed]}

More than a hundred different oxetanes have been synthesized.^{[citation needed]} Functional groups can be added into any desired position in the oxetane ring, including fully fluorinated (perfluorinated) and fully deuterated analogues. Major examples are:

Name	Structure	Boiling point, Bp [°C]
3,3-Bis(chloromethyl)oxetane		198[4]
3,3-Bis(azidomethyl)oxetane		165[5]
2-Methyloxetane		60[citation needed]
3-Methyloxetane		67[citation needed]
3-Azidooxetane		122[6]
3-Nitrooxetane		195[7]
3,3-Dimethyloxetane		80[citation needed]
3,3-Dinitrooxetane		–

Paclitaxel (Taxol) is an example of a natural product containing an oxetane ring. Taxol has become a major point of interest among researchers due to its unusual structure and success in the involvement of cancer treatment.^[8] The attached oxetane ring is an important feature that is used for the binding of microtubules in structure activity; however little is known about how the reaction is catalyzed in nature, which creates a challenge for scientists trying to synthesize the product.^[8]

Oxetanes are less reactive than epoxides, and generally unreactive in basic conditions,^[9] although Grignard reagents at elevated temperatures^[10] and complex hydrides will cleave them.^[11] However, the ring strain does make them much more reactive than larger rings,^[12] and oxetanes decompose in the presence of even mildly acidic nucleophiles.^[13] In non-nucleophilic acids, they mainly isomerize to allyl alcohols.^[14]

Noble metals tend to catalyze isomerization to a carbonyl.^[15]

In industry, the parent compound, oxetane polymerizes to polyoxetane in the presence of a dry acid catalyst,^[16] although the compound was described in 1967 as "rarely polymerized commercially".^[17]

• β-Propiolactone or 2-oxetanone.
• 3-Oxetanone