Synthesis and stereochemistry of indano[1,2‐d][1,3]oxazines and thiazines,new ring systems

A set of structurally varied indano1,2‐d]1,3]oxazines and thiazines, which are new ring systems, were prepared by ring‐closure reactions of amino alcohols 4–6. The reactions of cis‐ and trans‐1‐amino‐ and cis‐ 1‐benzylamino‐2‐hydroxymethylindane (4–6) with 1 equivalent of an aromatic aldehyde in methanol at room temperature resulted in three‐component equilibria (15a‐g), or a Schiff base (16), or a ring‐closure product alone (17a‐c), respectively, depending on the substitution or configuration of the starting amino alcohol. The ring‐chain tautomeric equilibria can be described by an equation of Hammett type.