Alkenes electrocyclic and sigmatropic photorearrangement

Selected theoretical and computational photochemistry references.16 480 534 535 538 603-610 Electrocyclic Photorearrangements 

Only the singlet state interconversions of conjugated dienes and cyclobutenes are taken into consideration here, because the triplet state is generally not involved in this process.596 There are two important factors that affect electrocyclization (1) reaction 

Apart from photocyclization reactions, simple trienes undergo many types of other phototransformations, including E Z photoisomerization (Section 6.1.1), sigmatropic shifts (see later) or photoadditions (Section 6.1.4). For example, conformational control and possibly equilibration between the excited conformers result in a 

Case Study 6.3 Mechanistic photochemistry - previtamin D photochemistry 

Vitamin D3 is naturally synthesized in human skin by a spontaneous thermal antarafacial hydrogen [l,7]-sigmatropic shift in previtamin D3, which is produced from 64 upon solar UVB irradiation in the first step.621 

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