Sodium Iodide-Triphenylphosphine-Mediated Photoredox Alkylation of Aldimines

Abstract

The photoredox reactions involving electron donor-acceptor (EDA) complexes have attracted significant attentions in the last decade. Very recently, the sodium iodide-triphenylphosphine-N-acyloxyphthalimide EDA complex has been discovered and employed in developing several net redox-neutral photoreactions. Herein, the EDA complex has been applied in a net reductive setup for the first time to establish a photoredox alkylation of aldimines without photosensitizer. The reaction affords not only high yields for secondary, tertiary and α-heterosubstituted alkyl radicals, but also high yields for primary alkyl radicals, and moderate to high yields for electron-rich or secondary benzylic radicals, two difficult groups of radicals in previous studies. This work provides an efficient and reliable approach for the synthesis of unnatural amino acids and amines.

Electron donor–acceptor complex-catalyzed photoredox reactions mediated by DIPEA and inorganic carbonates

“…During our previous work, 14 we noticed that an orange colour appeared upon mixing NHPI esters and DIPEA in methylene chloride (DCM). Further study confirmed the formation of an EDA complex between NHPI esters and DIPEA.…”

“…In the screening of alkali metal carbonates, Na 2 CO 3 was found to be less effective (entry 11), and no reaction took place with K CO 3 and Cs 2 CO 3 (entries 12 and 13). Significantly improved results were obtained in the reactions under violet light (entries [14][15][16][17]. The reactions proceeded significantly faster (taking ca.…”

“…Differing from chain reactions initiated at the cost of donors, 12 donor catalysts in their reactions are regenerated after radical generation. In our recent efforts to create radical approaches for the alkylation of aldimines, 13,14 we have established a high-yield photoredox decarboxylative alkylation of imines catalyzed by an iodide EDA complex. 14 In this work, we reveal that diisopropylethylamine (DIPEA, Hünig's base) could form EDA complexes with alkyl N -hydroxyphthalimide esters (NHPI esters) and alkali metal carbonates, and catalyse photoredox decarboxylative radical reactions of NHPI esters with various radical acceptors (Fig.…”

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

“…Simultaneously, Shen and colleagues made a notable contribution by disclosing a NaI/PPh 3 EDA complex-mediated photoredox alkylation of aldimines 20 ( Scheme 11 ) [ 20 ]. This newly developed method offered a reliable and efficient route for the synthesis of unnatural amino acids and amines.…”