215719-46-3Relevant academic research and scientific papers
Unusual cyclodimerization of small cyclic ethers via neighboring carbonyl-group participation and cation transfer
Kanoh, Shigeyoshi,Nishimura, Tomonari,Naka, Masashi,Motoi, Masatoshi
, p. 7065 - 7074 (2002)
Oxetanes having both a carbonyl functional group and a phenyl group at the 3-position bring about unusual cyclodimerization under the influence of trifluoromethanesulfonic acid, to give a cis/trans-isomer mixture of substituted 1,3-dioxanes via neighboring carbonyl-group participation, cation transfer including phenonium rearrangement, and cyclodimerization. Oxiranes having a carbonyl functional group also undergo a similar cyclodimerization to form a 1,3-dioxolane ring. No phenyl substituent is required in the cases of the oxiranes, because the cation transfer process involves a 1,2-hydride shift alone. These five- and six-membered cyclic acetals are quite different from ring-expanded cyclic ether dimers expected simply from the back-biting reaction known in the cationic ring-opening polymerization of oxiranes and oxetanes.
Isomerization of cyclic ethers having a carbonyl functional group: New entries into different heterocyclic compounds
Kanoh, Shigeyoshi,Naka, Masashi,Nishimura, Tomonari,Motoi, Masatoshi
, p. 7049 - 7064 (2007/10/03)
Oxiranes (epoxides) and oxetanes having a carbonyl functional group are chemoselectively isomerized to different heterocyclic compounds via Lewis acid-promoted 1,6- and 1,7-intramolecular nucleophilic attacks of the carbonyl oxygen on the electron-deficient carbon neighboring the oxonium oxygen: for example, cyclic imides to bicyclic acetals, esters to bicyclic orthoesters, sec-amides to 4,5-dihydrooxazole or 5,6-dihydro-4H-1,3-oxazines, and tert-amides to bicyclic acetals or azetidines. The intramolecular attack of a 1,5-positioned carbonyl oxygen predominantly results in a propagating-end isomerization polymerization. On the other hand, cyclic ethers having a 1,8- or farther positioned carbonyl group undergo conventional ring-opening polymerization. A tetrahydrofuran (oxolane) ring does not open, even with a 1,6-positioned carbonyl group.
