Improved Preparation of 9-Oxabicyclo(3.3.1)nona-2,6-diene

摘要

In the course of our work we needed ready access to highly functionalized eight-membered ring compounds and thus required a convenient method to prepare substantial quantities of 9-oxabicyclo nona-2,6-diene. 1,5-Cyclooctadiene (1,5-COD), is easily available and very inexpensive. Transannular additions of electrophilic reagents are well-known and many of the products can be transformed to the desired compound. There are many published routes, of more or less value. Probably the most convenient initial functionalization is given in the French patent literature. This performic acid oxidation provides, as shown by Ganter and co-workers, a mixture of the bicyclic diols. Direct dehydration to the oxy-bridged diene is not clean. The corresponding dibromides and diacetates have been made and converted by base-induced elimination or flash pyrolysis, respectively. We report here a simple alternative, which we find much more satisfactory and quite reproducible.