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Figure 6
Illustrations for the crystal structure of 4a: (a) a two-dimensional herringbone layer via N—H⋯N hydrogen; (b) packing of layers on top of each other to form infinite stacks. Note that the double bonds are aligned within the stacks to undergo double [2 + 2] reaction.

IUCrJ
Volume 2| Part 5| September 2015| Pages 523-533
ISSN: 2052-2525
https://doi.org/10.1107/S2052252515009987