| Summary: | Three isomeric (benzyloxythienyl)oxazolines <b>9</b>, <b>11</b> and <b>13</b> have been prepared and are found, upon treatment with a strong base, to undergo either Wittig rearrangement or intramolecular attack of the benzylic anion on the oxazoline function to give products derived from cleavage of the initially formed 3-aminothienofuran products. This pattern of reactivity is directly linked to the distance between the two reactive groups as determined by X-ray diffraction, with the greatest distance in <b>11</b> leading to exclusive Wittig rearrangement, the shortest distance in <b>13</b> giving exclusively cyclisation-derived products, and the intermediate distance in <b>9</b> leading to both processes being observed. The corresponding <i>N</i>-butyl amides were also obtained in two cases and one of these undergoes efficient Wittig rearrangement leading to a thieno[2,3-<i>c</i>]pyrrolone product.
|
|---|