Selective Synthesis of Z‐Cinnamyl Ethers and Cinnamyl Alcohols through Visible Light‐Promoted Photocatalytic E to Z Isomerization

Abstract

A photocatalytic E to Z isomerization of alkenes using an iridium photosensitizer under mild reaction conditions is disclosed. This method provides scalable and efficient access to Z‐cinnamyl ether and allylic alcohol derivatives in high yields with excellent stereoselectivity. Importantly, this method also provides a powerful strategy for the selective synthesis of Z‐magnolol and honokiol derivatives possessing potential biological activity.

Visible-light-mediated decarboxylative (E)-alkenylation of aliphatic carboxylic acids with aryl styryl sulfones under metal-free conditions

“…Firstly, we conducted a photo- E to Z isomerization of these compounds using an iridium-based photocatalyst for triplet-energy transfer, furnishing products 6a and 6b with ≥85 : 15 Z / E ratio. 30 These results exemplify that a careful selection of the photocatalyst has an essential impact on the configuration of the obtained olefin. Secondly, we capitalized on the fact that 2-phenoxycarboxylic acids are suitable substrates for this method by performing an iron-catalyzed allylic substitution of the phenoxy group in 3aa by a phenyl ring, 31 using an excess of phenylmagnesium bromide to obtain ( E )- 7 as a single isomer.…”

Heteroleptic Copper-Based Complexes for Energy-Transfer Processes: E → Z Isomerization and Tandem Photocatalytic Sequences

“…In contrast, indenyl–olefin 11 was only isolated in 56% Z , demonstrating the importance of the additional endocyclic carbonyl in 10 for achieving high selectivity in the isomerization. The ethyl- and methyl-substituted allylic alcohols 15 and 16 , could be photoisomerized using the copper-based photocatalyst at 400 nm to afford the Z -isomer in 94 and 97% Z , respectively. Phosphonate ester 17 was isomerized to a 92:8 Z / E ratio using the optimized copper catalyst under blue LEDs (previously reported under UV-light conditions) …”

Synthesis of Enantioenriched 3,4-Disubstituted Chromans through Lewis Base Catalyzed Carbosulfenylation

“…Following representative procedure A, the reaction of ( E )-(3-bromoprop-1-en-1-yl)­benzene (0.83 g, 4.2 mmol) with 4-(trifluoromethyl)­phenol (0.82 g, 5.1 mmol, 1.2 equiv) afforded 948 mg (81%) of 1g as a white solid. Spectroscopic data for 1g matched reported literature values and was used without further purification.…”