Metal‐Free Reductive Cleavage of CN and SN Bonds by Photoactivated Electron Transfer from a Neutral Organic Donor

Abstract

A photoactivated neutral organic super electron donor cleaves challenging arenesulfonamides derived from dialkylamines at room temperature. It also cleaves a) ArC–NR and b) ArN–C bonds. This study also highlights the assistance given to these cleavage reactions by the groups attached to N in (a) and to C in (b), by lowering LUMO energies and by stabilizing the products of fragmentation.

Cs2CO3‐Promoted Direct N‐Alkylation: Highly Chemoselective Synthesis of N‐Alkylated Benzylamines and Anilines

“…Ethyl Phenylglycinate (6k): Following the general procedure, the reaction of aniline ( 5a , 196 µL, 2.12 mmol), ethyl bromoacetate ( 2h , 118 µL, 1.06 mmol) and cesium carbonate (345 mg, 1.06 mmol) in anhydrous DMF (4.0 mL) at 60 °C for 5 h, afforded compound 6k as a light‐brown solid (137 mg, 72 %) after silica gel purification (CH 2 Cl 2 /pentane, 3:1), m.p. 56–57 °C (amorphous) . 1 H NMR (400 MHz, CDCl 3 ): δ = 1.30 (t, J = 7.2 Hz, 3 H), 3.90 (s, 2 H), 4.25 (q, J = 7.2 Hz, 2 H), 4.28 (br.…”

Powerful Bispyridinylidene Organic Reducing Agents with Iminophosphorano π‐Donor Substituents

“…The most powerful and intensively studied organic reducing agents are compounds A (−1.20 V vs. SCE),5, 10–12 and bispyridinylidenes B a (−1.24 V vs. SCE) and C a (−1.27 V vs. SCE) 2. 3, 7, 13–19 These ground‐state electron donors have been used in the reduction of organic substrates such as aryl halides,5, 7, 13, 20 sulfones and arenesulfonamides,7, 10 Weinreb amides,16 acyloin derivatives,17 triflates and triflamides 18…”

“…10, 15, 21 The desire to reduce these challenging substrates has led Murphy and co‐workers to utilize photoexcitation to boost the reducing power of the reagents. Indeed, upon photoactivation, B a is able to reduce difficult substrates such as activated benzenes, N , N ‐dialkyl arenesulfonamides, benzylic esters and ethers, benzyl malonates and cyanoacetates,15, 19, 21, 22 which could not be reduced by B a in the ground state. Unfortunately, the majority of the photoassisted reductions involve the use of excess reducing agent and require longer reaction times (typically 72 h) 3…”

Facile preparation and isolation of neutral organic electron donors based on 4-dimethylaminopyridine

“…2 Electron donors based on alternate scaffolds, that are easier to prepare and offer similar, or even slightly increased, reducing power became available when Murphy described an elegant synthesis for amino-substituted bispyridinylidenes such as 4a (E 1/2 (DMF) = -1.24 V vs SCE). 7,11,12 Their facile preparation has led these DMAP-derived electron transfer agents to find applicability in the polymerization of various activated alkene and cyclic ester monomers, 13 as well as the ground-state or photoexcited reduction of a variety of substrates including aryl halides, 11 Weinreb amides, 14 acyloin derivatives, 15 arenesulfonamides, 11 triflates and triflamides, 16 as well as benzylic C-O, 17 C-N, 18 and C-C bonds. 19 Most commonly, these reactions involve the in situ generation of the air and moisture sensitive electron donors via the reaction of easily handled pyridinium ion precursors with a strong base.…”