4π Electrocyclization

5 real reactions from the literature, on cyclic conjugated dienes and cyclobutenes. Each scheme shows starting materials, conditions and products, with the yield and reference where the source reports them.

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1. 4π electrocyclization: cyclopentadiene (a cyclic conjugated diene) with hν; THF gives bicyclo(2.1.0)pent-2-ene (the cyclobutene).

   4π electrocyclizationOrg. Synth. Coll. Vol. 6, p. 145

2. 4π electrocyclization: a cyclic conjugated diene with 100 C; 4e con gives the electrocyclic product.

   4π electrocyclizationAngew. Chem. Int. Ed. 2017, 56, 4839

3. 4π electrocyclization: (1Z,3E)-cycloocta-1,3-diene (a cyclic conjugated diene) with 80 C; 4e con gives the cyclobutene. 100% yield.

   4π electrocyclizationJ. Am. Chem. Soc. 1965, 87, 3996

4. 4π electrocyclization: a cyclobutene with mesitylene (solvent); 4e con gives the cyclic conjugated diene. 78% yield.

   4π electrocyclizationJ. Org. Chem. 1989, 54, 2267

5. 4π electrocyclization: a cyclic conjugated diene with hv; 4e dis gives the cyclobutene.

   4π electrocyclizationTetrahedron Lett. 1981, 22, 3115