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HOWELL RESEARCH GROUP DEPARTMENT
OF CHEMISTRY |
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Dichotomy of Reactivity
of 1,5-Dioxaspiro[3.2]hexanes
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A
particularly interesting outcome was observed upon exploring the reactivity
of 1,5-dioxaspiro[3.2]hexanes 7. It was anticipated
that nucleophilic attack at the more reactive C6
would lead to alpha-substituted-beta-hydroxy
ketones 9. In fact, a range of carbon, oxygen, sulfur
and nitrogen nucleophiles provided alphaa-substituted-beta-hydroxy ketones
9. However, an unanticipated outcome resulted when
Lewis acid-containing nucleophiles were utilized: 2,2’-disubstituted
oxetanes 11 were isolated. It is likely that Lewis
acids induce the formation of an oxonium ion intermediate 10
which is captured by the nucleophile. The novel oxetane retained pathway
is being exploited in the synthesis of novel nucleosides and the total
synthesis of the natural products, laureatin and oxetin. |
| (1) Howell, A.R.;
Ndakala, A.J. J. Org. Chem. 1998, 63, 6098-6099. (2) Taboada, R; Ordonio, G. J. Org. Chem., 2003, 68, 1480-1488. |
