Routes to simple 3-substituted oxetanes
, PhD thesis, University of Salford.
This thesis describes syntheses and attempted syntheses of certain 3-substituted
oxetanes. Simple oxetanes bearing reactive substituents in the 3-position are required
since the polymerisation of these compounds is anticipated to lead to polymers of
potential use as energetic binders in rocket propellant systems. Oxetanes of particular
interest are 3-hydroxyoxetane, 3,3-bis(hydroxymethyl)oxetane, and 3-(hydroxymethypoxetane.
3-Hydroxyoxetane was prepared in three steps from epibromohydrin (I). Firstly,
Lewis acid-catalysed ring opening of the epoxide in the presence of acetic acid gave the
bromohydrin II. This was heated with ethyl vinyl ether and p-toluenesulphonic acid,
and cyclisation of the resulting ether III with strong base afforded the oxetane IV.
Deprotection gave 3-hydroxyoxetane (V).
3-Hydroxyoxetane (V) underwent reaction with dinitrogen pentaoxide, and the
resulting nitrate ester VI was polymerised to give poly-3-nitratooxetane 3,3-Bis(hydroxymethyl)oxetane (IX) was prepared from pentaerythritol (VIII)
via pyrolysis of the carbonate ester X, and by monobromination followed by
intramolecular Williamson reaction of the resulting bromohydrin XI.
Attempts have been made to synthesise 3-(hydroxyMethypoxetane (XII) by two
main routes. The first involved cyclisation of either 2-(hydroxymethyl)propane-1,3-diol
(XIII) or a protected derivative XIV to give either the oxetane XII itself or the
corresponding derivative XV. 2-(Hydroxymethyl)propane-1,3-diol (XHI) was itself prepared by deamination
of 2-amino-2-(hydroxymethyl)propane-1,3-diol (XVI) using hydroxylamine-0-
sulphonic acid in base, but it could not be cyclised directly.
2,2-Dimethy1-5-(hydroxymethyl)-5-nitro-1,3-dioxane (XVIII) was formed by
the reaction of 2-(hydroxymethyl)-2-nitropropane-1,3-diol (XVH) with 2-methoxypropene.
The dioxane XVIII was further protected by conversion to 2,2-dimethy1-5-
(methanesulphonyloxymethyl)-5-nitro-1,3-dioxane (XIX). Hydro-denitration of the
nitro-compound XIX using tri-n-butyltin hydride, yielded 2,2-dimethy1-5-
(methanesulphonyloxymethyl)-1,3-dioxane (XX), which was hydrolysed to the
corresponding diol XXI. Treatment of this methanesulphonyl ester XXI with strong
base afforded 3-(hydroxy/methypoxetane (XV).
An attempt to form 2(t-butyldimethylsilyloxymethyppropane-1,3-diol (XXII)
via a five-stage process from allyl t-butyldimethylsilyl ether (xxim) was unsuccessful. Cyclo-addition of the allyl ether XXIII with dichloroketene gave 3-(tbutyldimethylsilyloxymethyl)-
2,2-dichlorocyclobutanone (XXIV) which was dehalogenated
to give 3-(t-butyldimethylsilyloxymethyl)cyclobutanone (XXV). This
was converted to diethyl acetal XXVI, but the acetal failed to undergo Baeyer-Villiger
oxidation to 5-(t-butyldimethylsilyloxymethyl)-2-oxo-1,3-dioxane (XXVII). A second route to 3-(hydroxymethyl)oxetane (MI) involved the formation and
attempted cyclisation of the glycidyl ether XXVIII to give oxetane XXIX. The
epoxide XXVIII was prepared from ethyl bromoacetate and glycidol, but no cyclisation
could be effected.
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