Studies on the Polymerization of Acrolein Oxime. XVII. The Structure of the β-Form of the Bicyclic Trimer from Methacrylaldehyde Oxime

The thermal oligomerization of methacrylaldehyde oxime leads to 2,4,7-trimethylperhydroisoxazolo[2,3-a]pyridine-2,7-dicarbaldehyde dioxime (1). The β-form of 1 was separated, and its crystal structure was determined by X-ray analysis. It is monoclinic with space group P21/c, a=13.274(11), b=8.652(7), c=11.618(14) A, β=96.73(8)°, and Z=4. The molecules are linked by two N···O hydrogen bonds, with the N(13)···O(14) and N(8)···O(18) distance of 2.824(5) and 2.897(5) A respectively.