Electrochemical Formation of Cinnamaldehyde by the Electrolyte System N,N‐Diisopropylethylamine and 1,1,1,3,3,3‐Hexafluoropropan‐2‐ol

Abstract

The use of a supporting electrolyte has been a significant issue in electro‐organic chemistry because it can be wasteful and increase steps in terms of separation from target products. However, it is ideal for an electrolyte to play multiple roles in reactions, for example, as a feedstock or catalyst. We have discovered that the combination of N,N‐diisopropylethylamine (DIPEA) and 1,1,1,3,3‐hexafluoropropan‐2‐ol (HFIP) not only works as an electrolyte but also facilitates the electrochemical formation of cinnamaldehyde from benzaldehydes. We demonstrate that the synthesis of 20 cinnamaldehyde derivatives can be achieved by using this reaction. Isotope‐labeling experiments and 13C NMR investigations revealed the mechanistic aspects of this process, and confirmed that DIPEA is the C2 synthon of acetaldehyde and HFIP could also function as a Brønsted acid.

Direct photo-induced reductive Heck cyclization of indoles for the efficient preparation of polycyclic indolinyl compounds

“…The excited state potential E( S1* / S1− ) was estimated to be 1.15 V vs. Ag/AgCl ( S1 's E 0–0 = 2.9 eV; E pc ( S1 / S1− ) = −1.75 V), which is higher than the reported potential of E (DIPEA˙ + /DIPEA) (0.9 V vs. Ag/AgCl). 37 Therefore, upon excitation, S1 attains a triplet excited state, which accepts an electron from DIPEA to give one-electron reduced S1 ( Scheme 2 , species B) and DIPEA˙ + . (7) In situ formation of electron donor–acceptor complexes is another strategy for light-induced C–Cl bond activation.…”

“…The excited state potential E(S1*/S1 -) was estimated as 1.15 V vs Ag/AgCl (S1's E 0-0 = 2.9 eV; E pc (S1/ S1 -) = -1.75 V), which is higher than the reported potential of E(DIPEA •+ /DIPEA) (0.9 V vs Ag/AgCl). 37 shows an intense absorption at 250-300 and weak absorption beyond 325 nm. For indole substrate S1 (0.1 M), there is an intense absorption at 250-330 nm, with absorption tail ending at ~390 nm (Figure S11).…”

Electrosynthesis 2.0 in 1,1,1,3,3,3‐Hexafluoroisopropanol/Amine Mixtures

“…The Chiba group recently identified a novel mode of reactivity and reported a HFIP/DIPEA‐based aldol reaction, whereby the ethyl group of DIPEA additionally serves as a C 2 source . Mechanistic studies revealed that DIPEA and HFIP play a significant role within this reaction.…”

“…[35] Many more seminal applications of this powerful combination have been recently published and will be discussed within this review. [36][37][38][39][40]…”

“…Subsequently, our group first used a simple tertiary amine base without additional salt or reagents in a formal benzyl‐aryl cross‐coupling reaction, demonstrating the potential of this approach (Scheme ) . Many more seminal applications of this powerful combination have been recently published and will be discussed within this review …”