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

A set of structurally varied indano[1,2-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 I 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.