3,3′-(Ethane-1,2-di­yl)bis­(3,4-dihydro-2H-1,3-benzoxazine)

The title compound, C₁₈H₂₀N₂O₂, was prepared by Mannich-type reaction of phenol, ethane-1,2-diamine and formaldehyde. The heterocyclic rings adopt half-chair conformations. The acyclic methyl­ene groups attached to the N atoms are in an axial position. In the crystal, weak C—H...O hydrogen bonds link the mol­ecules into dimers. These dimers are further connected via C—H...π contacts.

3,3′-(Ethane-1,2-diyl)bis(6-meth­oxy-3,4-dihydro-2H-1,3-benzoxazine) mono­hydrate

The asymmetric unit of the title compound, C₂₀H₂₄N₂O₄·H₂O, contains one half-organic mol­ecule (an inversion centre generates the other half of the mol­ecule) and a half-mol­ecule of water (the O atom has site symmetry 2). The near planarity of the fused-benzene ring is illustrated by the very small deviations of all the atoms from the plane [largest deviation = 0.0092 (11) Å. The six-membered N,O-containing ring adopts a half-chair conformation. The observed N—CH₂ and CH₂—O bond lengths can be correlated to the manifestation of an anomeric effect in the N—CH₂—O unit. In the crystal, the mol­ecules are connected into zigzag chains parallel to [001] through O—H...N hydrogen bonds formed between the oxazinic N atom and the solvent water mol­ecule. The chains are consolidated by C—H...O inter­actions.