Bildung von 4‐, 5‐ und 6gliedrigen Heterocyclen durch ambidoselektive Ringschlüsse von Enolat‐Ionen

Abstract

Formation of 4‐, 5‐ and 6‐membered heterocycles by ambidoselective cyclization of enolate anionsN‐Acylmethyl‐N‐chloracetyl‐2,6‐dimethylanilines 4 were cyclized with base to 4‐, 5‐ or 6‐membered ring compounds, depending on the substituent R2 (Scheme 2). All products can be rationalized as derived from the intermediate enolate anions a and b. The enolate anion a reacts by intramolecular alkylation to yield either 1, 4‐oxazines 5 or azetidines 6 (Schemes 1, 3 and 7). The regioselectivity observed is expected on the basis of the allopolarization principle. The enolate anion b reacts only with formation of a new CC bond (Scheme 5). Comparison with the behaviour of the 2, 6‐unsubstituted anilines 9, 1a and 12, shows a strong dependence not only on electronic but also on steric factors (Scheme 4 and 6).