We report herein an ew method for the photoredox activation of boronic esters.U sing these reagents,a ne fficient and high-throughput continuous flow process was developed to perform adual iridium-and nickel-catalyzed C(sp 2)-C(sp 3) coupling by circumventing solubility issues associated with potassium trifluoroborate salts.F ormation of an adduct with apyridine-derived Lewis base was found to be essential for the photoredox activation of the boronic esters.B ased on these results we were able to develop afurther simplified visible light mediated C(sp 2)-C(sp 3)coupling method using boronic esters and cyano heteroarenes under flowc onditions.

An efficient method for the synthesis of monoprotected syn‐ or cis‐1,2‐diol derivatives by reduction of easily accessible α‐(2,2,6,6‐tetramethylpiperidinyloxy) ketones is reported. The α‐(tetramethylpiperidinyloxy) group as the stereodirecting group induces in unhindered acyclic or cyclic ketones complete syn‐ or cis‐diastereoselectivity, respectively, with L‐Selectride. For more hindered derivatives, where L‐Selectride becomes unreactive, LiAlH4 proved effective, essentially showing the same high selectivity. The diastereoselectivity of the reduction can be rationalized for acyclic ketones by the Felkin–Anh model, whereas for cyclic substrates, attack from the face opposite to the tetramethylpiperidinyloxy group predictably prevails with high selectivity regardless of the substitution pattern. The liberation of free diols was achieved by reductive N–O bond cleavage of the alkoxyamine unit.

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anti‐β‐Amino‐α‐(aminoxy) esters or amides are synthesized by merging polar asymmetric aza‐Michael additions of lithium 1‐phenylethylamides to α,β‐unsaturated carboxylic acid derivatives and diastereoselective radical couplings with the persistent free radical TEMPO mediated or catalyzed by ferrocenium hexafluorophosphate. Aliphatic α,β‐unsaturated carboxylic derivatives gave good to excellent anti‐diastereoselectivity for the radical coupling step, whereas the selectivity remained lower for cinnamic acid derivatives. The method allows the convenient introduction of a protected oxygen functionality, which is stable to acidic, basic, hydride and hydrogenolytic reductive conditions, but can be deprotected with zinc and acetic acid in the presence of TBDMS and Boc groups without noticeable epimerization. The tandem aza‐Michael/oxygenation strategy was applied in total syntheses of the TH2 cytokine secretion modulator cytoxazone, and dipeptide fragments of the anti‐β‐amino‐α‐hydroxy acid containing macrocyclic peptides perthamide C and largamide H.

In the light you will find the road (Led Zeppelin): Photoredoxkatalyse mit sichtbarem Licht erhellt den Weg, um Reaktivitätsbeschränkungen von Alkylnucleophilen in Kreuzkupplungen zu überwinden. Die iridiumkatalysierte oxidative Photoredoxaktivierung von Alkyltrifluorboraten oder aliphatischen Carbonsäuren ergibt Alkylradikale, die nickelkatalysierte Kreuzkupplungen eingehen.