The intermediacy of oxetanes in the prins reaction

Synthesis of Novel Hapten Derivatives of 1α,25-Dihydroxy-vitamin D3 and Its 20-Epi Analogue1

“…It has been postulated that the mechanism of the ene reaction in certain cases involves the formation of a 2 + 2 transition state complex (an oxetane) before the rate-determining step to the ene product . Alternatively, the oxetane could be formed via an intermediate characteristic of the Prins reaction . Thus, instead of the concerted addition process typical of the ene reaction, the alkene attacks the formaldehyde, thereby generating a tertiary carbenium ion that collapses to the oxetane 22 .…”

Metal(IV) phosphate catalysed retro-Prins reaction involving an oxetane intermediate

“…1 The uncatalysed reaction (1) is believed to proceed through an 'ene' mechanism, 2 but various substrates undergoing acid-catalysed Prins reactions have been reported to proceed through a carbocation, 3 through a mechanism not involving a carbocation, 4 and through the formation of an oxetane intermediate, 5 as well as an ene reaction. 6 The retro-Prins reaction has proved useful synthetically, 7 but it is known only as a thermal elimination. One mechanistic study has shown clearly that the thermal retro-Prins elimination can proceed through an uncatalysed concerted reaction with hydrogen transfer [reaction (2).]…”

Reaction of Isoeugenol with Formaldehyde in Basic Medium: Formation of trans-4-(4-Hydroxy-3-hydroxymethyl-5-methoxy)-5-methyl-1,3-dioxane and its Transformation into the Tricyclo[5.2.2.02,6]undecane System†

“…In this context, it may be mentioned that the intermediacy of oxetanes has been proposed during the acidcatalysed Prins reaction of alkenes. 5 It may also be noted that the hydroxymethylation of eugenol 11, wherein the double bond in the side chain is not conjugated, smoothly furnished the usual compound 12 (Scheme 3) upon treatment with formaldehyde and base.…”