Oxetanes reaction with organolithium reagents

Derivatives of azete are only known as unstable reaction intermediates. Oxetane and azetidine are considerably less reactive than their three-membered connterparts (oxetane reacts with hydroxide anion 10 times more slowly than does oxirane), but nonetheless do undergo similar ring-opening reactions, for example oxetane reacts with organolithium reagents in the presence of boron triflnoride, or with cuprates, and azetidine is opened on heating with concentrated hydrochloric acid. Azetidininm ions react mnch more easily with nucleophiles. ... 

Other chiral oxetanes used to generate chiral y-oxido functionalized organolithium intermediates are 306-309, which gave the expected enantiopure products by reaction with non-prochiral electrophiles"" °. In all cases, when prochiral electrophilic reagents were used, a mixture of the corresponding diastereomers was obtained in variable proportions depending on the electrophile, which could be easily separated by column chromatography. 

The reaction of oxetanes with Grignard reagents and organolithium compounds is well known and has been useful, particularly with oxetane itself. A recent application involves use of the reaction of isopentylmagnesium bromide with oxetane as the first step of a synthesis of an insect pheromone (equation 43) (76CB3375). The Grignard reaction with 2-methyloxetane and 2-phenyloxetane is less satisfactory, due to the extensive formation of by-products. 

---