Applications of Norrish type I and II reactions in the total synthesis of natural products: a review

Abstract

Natural products and their analogue have played a key role in the drug discovery and development process. In the laboratory, the total synthesis of secondary metabolites is very useful in ascertaining the hypothetical complex structure of molecules of natural origin. Total synthesis of natural products using Norrish type I and II reactions as a crucial step has been explored in this overview. Norrish reactions are important photo-induced transformations of carbonyl compounds in organic synthetic chemistry and are connected in numerous industrially and biologically relevant procedures and the processing of carbonyl compounds in the atmosphere. The present review tries to focus on the brilliant applications of Norrish type I and II photochemical reactions as a key step in the total synthesis of natural products and highlights on natural sources, structures, and biological activities of the promising natural products for the first time elegantly.

Photochemical Ring Editing: Access to Privileged 1,2,5-Thiadiazole Scaffolds via Efficient Carbon Excision from Thiadiazines Under Ambient, Aerobic Conditions

“…Therefore, we confirm: (i) the additional oxygen atoms installed through the reaction result on the ring sulfur and external amide carbonyl; (ii) the C4 centred carbonyl does not migrate and; (iii) the cleavage of the C-C bond during the ring contraction does not depend on Norrish-type radical processes induced by direct excitation of the carbonyl. 40 To assess the selectivity preferences for the reaction, with respect to the excised carbon, we screened a series of asymmetric thiadiazines 30a-40a with different R-groups substituted at the 3-and 5-ring positions. Pleasingly, most asymmetric compounds showed excellent chemoselectivity and a single product was isolated.…”

Merging the Norrish type I reaction and transition metal catalysis: photo- and Rh-promoted borylation of C–C σ-bonds of aryl ketones

“…The Norrish type I reaction is one of the representative photoreactions of ketones to cleave C–C σ-bonds α to the carbonyl moiety (α-cleavage reaction) upon ultraviolet irradiation. 8 Although its synthetic application has been largely devoted to intramolecular reactions of cyclic dialkyl ketones, 9 it is also reported that alkyl aryl ketones (ArCOR) generate a pair of an alkyl radical (R˙) and an aroyl radical (ArCO˙) reversibly, which undergo hydrogen abstraction to give an aldehyde along with an alkene. 10 This could be a promising approach toward intermolecular arylation reactions using ketones as aryl sources if the generated aroyl radical decarbonylates efficiently to form an aryl radical (Ar˙), which could be utilized for arylation of other substrates ( Fig.…”

Samarium(III) Triflate in Organic Synthesis: a Mild and Efficient Catalyst

“…[10,11] Besides, catalysis is a potential synthetic tool for the synthesis of promising organic molecules as well as the total synthesis of bioactive secondary metabolites for accomplishing a high degree of molecular complexity from comparatively simple building blocks. [12][13][14][15][16][17][18][19][20][21][22] Triflate salts of the lanthanides, commonly known as lanthanide triflate, have been examined for their application in the synthesis of organic molecules as a water-tolerant Lewis acid. [23] Lanthanides display variable oxidation states such as + 2, + 3, and + 4 oxidation states.…”

“…One of the fundamental pillars of organic chemistry is catalysis; the catalyst increases the targeted reaction rate by lowering the activation energy in several industrial syntheses, energy conversion, and environmental pollution control [10,11] . Besides, catalysis is a potential synthetic tool for the synthesis of promising organic molecules as well as the total synthesis of bioactive secondary metabolites for accomplishing a high degree of molecular complexity from comparatively simple building blocks [12–22] . Triflate salts of the lanthanides, commonly known as lanthanide triflate, have been examined for their application in the synthesis of organic molecules as a water‐tolerant Lewis acid [23] .…”