Redox-Selective Iron Catalysis for α-Amino C–H Bond Functionalization via Aerobic Oxidation

Abstract

Single-electron oxidation and α-deprotonation of tertiary anilines using Fe­(phen)3(PF6)3 afford α-aminoalkyl radicals, which can be coupled with electrophilic partners to afford various tetrahydroquinolines. Mechanistically, the Fe­(phen) n 2+/3+ catalytic cycle is maintained by O2 or a TBHP oxidant, and the presence of the oxygen bound iron complex, Fe­(III)–OO­(H), was elucidated by electron paramagnetic resonance and electrospray ionization mass spectrometry. This redox-selective nonheme iron catalyst behaves similarly to bioinspired heme iron catalysts.

Iron Redox Shuttles with Wide Optical Gap Dyes for High‐Voltage Dye‐Sensitized Solar Cells

“…[Fe(tpy) 2 ][PF 6 ] 3 is reported [17] to have been synthesized according to a general procedure [18] . In our hands, we have found a recently reported route to Fe 3+ pyridyl compounds with PbO 2 as an oxidant to arrive at the desired [Fe(tpy) 2 ][PF 6 ] 3 complex [19] . Briefly, [Fe(tpy) 2 ][PF 6 ] 3 begins with complexation of Fe(SO 4 ) ⋅ 7H 2 O in H 2 O with 2 equivalents of 2,2′;6′,2“‐terpyridine followed by addition of 1 M H 2 SO 4 and excess PbO 2 .…”

Photochemical Reaction of N,N‐Dimethylanilines with N‐Substituted Maleimides Utilizing Benzaldehyde as the Photoinitiator

“…The past decade, various methods for the synthesis of tetrahydro‐pyrrolo[3,4‐c]quinolinones, which via aromatization can lead to the desired pyrrolo[3,4‐c]quinolinones, [7d,e] have been developed, primarily focusing on the oxidative annulation by utilizing a catalyst and either air or oxygen or a chemical reagent as the oxidant. Various examples exist in literature employing mainly metal catalysts [7] .…”

“…Various examples exist in literature employing mainly metal catalysts [7] . For example, Kang and coworkers showed that the reaction can be performed with the use of an iron (III) complex and as the external oxidant, which is essential for the completion of the transformation, they used either TBHP or air (Scheme 1A) [7e] . Similarly, Gogoi and coworkers used CeO 2 as the catalyst and air as the oxidant, in order to perform this oxidative annulation (Scheme 1B) [7d] .…”

Visible‐Light‐Induced Synthesis of 1,2,3,4‐Tetrahydroquinolines through Formal [4+2] Cycloaddition of Acyclic α,β‐Unsaturated Amides and Imides with N,N‐Dialkylanilines

“…The reaction of acyclic α,β‐unsaturated compounds with N , N ‐dialkylanilines has the possibility of enabling the synthesis of 1,2,3,4‐THQs possessing a wide variety of substituents with control of trans / cis diastereo‐ and enantioselectivity. However, there are very few reports on photo‐ and non‐photoinduced reactions with acyclic α,β‐unsaturated compounds, for example, arylidene malononitrile, [5a, 21] dialkyl fumarate, [5b, 7d, 20d] and 1‐(2‐alkenoyl)‐3,5‐dimethylpyrazole [22] . Among the three types of acyclic α,β‐unsaturated compounds, 1‐(2‐alkenoyl)‐3,5‐dimethylpyrazole has been utilized for the reaction of N , N ‐dialkylaniline to give 1,2,3,4‐THQs in which a bidentate chelation complex of a chiral Lewis acid, ( R , R )‐DBFOX/Ph ⋅ Ni II (( R , R )‐DBFOX/Ph=( R , R )‐4,6‐dibenzofurandiyl‐2,2′‐bis(4‐phenyloxazoline)), [23] with 1‐(2‐alkenoyl)‐3,5‐dimethylpyrazole serves as a photocatalyst; [22] however, only two reactions have been demonstrated.…”