Photochemical strategies for the construction of polycyclic molecules

Photochemical Approaches to Complex Chemotypes: Applications in Natural Product Synthesis

“…As a result, a number of fascinating total syntheses of natural products have been achieved, which highlight the remarkable power of UV light for constructing advanced polycyclic carbon skeletons. 27 , 32 , 33 The use of UV light for bond assembly has been known for a long period of time. Trommsdorff found in the early 19th century that crystals of the sesquiterpene santonin reacted upon exposure to sunlight, which may be considered the birth of photochemistry.…”

Photocycloaddition of Arenes and Allenes

“…28 The reaction was also carried out on a preparative scale (0.15-0.79 mmol), and the identity of the products were established by full spectroscopic analyses; the identity of the core structures was confirmed by X-ray analysis of 2l and 3b. 16 Substitution on position 3 of the aromatic ring with electron releasing substituents ( Table 3, entries [2][3][4] accelerates the reaction considerably and enhances the formation of the para-photocycloaddition product, whereas the substituents on the position 4 show an opposite effect. For example irradiation of the 4-methyl-or 4-methoxy-substituted analogue leads to remarkably longer reaction times and no formation of the bicyclo[2.2.2]octadiene product (Table 3, entries 5 and 6).…”

“…Activation by transition metal complexes is one way of conferring an alkene or diene character to aromatic rings, but the main approach is the photochemical excitation. 1,2,3,4,5 While the meta photocycloaddition is very well established 6,7 and has been applied many times in organic synthesis, 8 the ortho- 9,10 and particularly the para-versions 11 have not yet gained much attention as they occur rarely and usually with low yield. However, these two modes also have the potential to create significant complexity, with the formation of a new ring and up to four new stereocenters.…”

Synthesis of Benzocarbazole Derivatives by Photocyclization

“…The application of photochemical reactions for the synthesis of complex organic compounds, which are difficult to prepare by conventional methods, is an important and rapidly growing area of research in organic chemistry . For example, UV irradiation is used in key steps of the synthesis of a series of natural and biologically active compounds . Photoreactions provide the basis for the synthesis of fused carbo‐ and heterocycles.…”