Oxetane, basicity compounds

Cyclobutane has not been polymerised cationically (or by any other mechanism). Thermochemistry tells us that the reason is not thermodynamic it is attributable to the fact that the compound does not possess a point of attack for the initiating species, the ring being too big for the formation of a non-classical carbonium ion analogous to the cyclopropyl ion, so that there is no reaction path for initiation. The oxetans in which the oxygen atom provides a basic site for protonation, are readily polymerizable. Methylenecyclobutane polymerises without opening of the cyclobutane ring [72, 73]. 

Oxetanes are rather basic materials and are inert to attack by bases. However, as stated above, anionic polymerization of thietanes has been reported [67], Significantly, in anionic polymerizations initiated by organo-lithium compounds the propagating end is a carbanion rather than a thiolate species viz. 

Cyclic ethers with three- and four-membered rings represent a special group of ethers the epoxides (oxiranes) and oxetanes, respectively. These compounds are very reactive and have important uses in industry. The most basic cyclic ether, oxirane, ethylene-oxide is used for artificial maturation of vegetables. 

In a similar way it has been shown that reaction of mesylate 22, under aqueous basic conditions, affords the oxetane acid 23. This latter compound was used for a formal synthesis of the anti-viral oxetanocin. (See also Vol. 24, p. 217 and p. 176 for similar work.) The synthesis of other branched-chain nucleosides is covered in Chapter 20. 

Under basic conditions, tetra-acetylethylene leads to the cyclopentenone derivative (12). The reaction of (12) with excess diazomethane has been shown to give four compounds, i.e. the two expected cyclopropane derivatives and the two oxetans (13) and (14). ... 

---