Investigation into the reactions of aliphatic methoxydiazo-ketones upon treatment with boron trifluoride etherate

This research was a study of the possible cyclization reactions of the aliphatic methoxydiazoketones (I) and (II) upon treatment with BF3 etherate. Previous work in this area had dealt with aromatic systems. J. Moore and H. Shaffer (10) showed that 1-diazo-3-(o-anisyl)-2-propanone (III) is converted in about 35% yield to chromanone (IV) upon treatment with BF3. They obtained lesser amounts of chromanone and larger amounts of open chain products when mineral acids were employed. Diazoketones such as (V) and (VI) have shown a pronounced tendency to form four-membered rings upon treatment with mineral acids. (8) No open chain products were isolated in the latter case even in the presence of excess nucleophile. The formation of five and six-membered rings has generally been limited to the sterically favorable ortho-substituted aromatic forms. Based on the fact that the Lewis Acid, BF3, gave the best yield of cyclic product in the aromatic system a similar result might be expected from the aliphatic series. The object of this research was to produce the cyclic compounds oxetanone-3 (VII) and tetrahydro-3-furanone (VIII) by the BF3 method. The diazoketones which appear in this paper will be written as RCOCHN2 although the actual structure is a resonance hybrid of the three forms