Straightforward Synthesis of Fluorinated Enals via Photocatalytic α-Perfluoroalkenylation of Aldehydes

Abstract

(Per)­fluorinated substances represent an important compound class with regard to drug design and material chemistry. We found a mild, operationally simple, and inexpensive photocatalytic perfluoroalkenylation reaction giving tetrasubstituted, highly electron-deficient enals straight from aldehydes. This one-step reaction tolerates various functional groups and can be applied to a wide range of substrates giving the products in yields of 52–84%.

Recent Advances in Photoinduced Perfluoroalkylation Using Perfluoroalkyl Halides as the Radical Precursors

“…In 2021, Czekelius and Wulkesch 76 reported a photoinduced metal-free β-perfluoroalkenylation of aldehydes via C–F bond cleavage leading to polysubstituted enals (Scheme 45 ). Aldehydes with various functional groups and perfluoroalkyl iodides with various chain lengths were suitable substrates.…”

Water facilitated photolysis of perfluoroalkyl iodidesviahalogen bonding

“…Since then, various Lewis bases have been developed for light-induced perfluoroalkylation of unsaturated bonds via XB (Scheme 1B). 11 Despite this progress, most of these methods require superstoichiometric amounts of amines or other Lewis bases. Recently, Czekelius and co-workers developed an interesting catalyzed photoactivation of perfluoroalkyl iodides using catalytic amounts of phosphines.…”

Catalyst-Free Visible-Light-Mediated Iodoamination of Olefins and Synthetic Applications

“…19 We next investigated the tosyl and nosyl deprotection for representative examples (Scheme 3F). While morpholine derivative 14 and piperidine 15 can smoothly be tosyldeprotected under mild reductive conditions, the introduced nosyl goup offers the possibility to deprotect more functionalized molecules like Ns-5 under much milder redox-neutral conditions, giving halostachine (20) in good yields.…”

“…Notably, this principle of photochemical iodide activation can be also found with phosphines. 20 In conclusion, we have developed a highly efficient protocol to directly furnish a broad scope of iodoamination of commercially available alkenes utilizing simple and abundant sulfonamides and NIS under visible-light irradiation. The protocol excels through high yields and environmentally benign reaction conditions, omitting any metal or catalyst species and being driven in a green and biodegradable solvent.…”

“…The latter adds to the alkene 1 , forming radical intermediate VII , which now can abstract iodide from the starting complex I to deliver the final product 4 with concurrent regeneration of nitrogen-centered radical VI . Notably, this principle of photochemical iodide activation can be also found with phosphines …”