Transition-Metal-Free Synthesis of N-Arylphenothiazines through an N- and S-Arylation Sequence

Gram-Scale Synthesis of the N-Phenyl Phenothiazine Photocatalyst by Benzyne Addition

N-phenyl phenothiazine is one of the most reducing photoredox catalysts. Its synthesis commonly requires transition metal catalyzed cross-coupling reactions. Here we show the syntheses of four aryl phenothiazines via a benzyne route, including a multi-gram scale synthesis of N-phenyl phenothiazine. While yields are modest, the simplicity, low cost, and lack of requirement for cross-coupling catalysts in this synthesis will be attractive to users of this photocatalyst.

Recent Advances in the Smiles Rearrangement: New Opportunities for Arylation

The Smiles rearrangement has undergone a renaissance in recent years providing new avenues for non-canonical arylation techniques in both the radical and polar regimes. This short review will discuss recent applications of the reaction (from 2017 to late 2021), including its relevance to areas such as heterocycle synthesis and the functionalization of alkenes and alkynes as well as glimpses at new directions for the field.

1 Introduction

2 Polar Smiles Rearrangements

3 Radical Smiles: Alkene and Alkyne Functionalization

4 Radical Smiles: Rearrangements via C–X Bond Cleavage

5 Radical Smiles: Miscellaneous Rearrangements

6 Conclusions

Diarylamine Synthesis via Desulfinylative Smiles Rearrangement

Diarylamines are obtained directly from sulfinamides through a novel rearrangement sequence. The transformation is transition metal-free and proceeds under mild conditions, providing facile access to highly sterically hindered diarylamines that are otherwise inaccessible by traditional S_NAr chemistry. The reaction highlights the distinct reactivity of the sulfinamide group in Smiles rearrangements versus that of the more common sulfonamides.

Extended phenothiazines: synthesis, photophysical and redox properties, and efficient photocatalytic oxidative coupling of amines

Herein, we successfully developed a ring-fusion approach to extend the conjugation length of phenothiazines that were demonstrated to be efficient photocatalysts for visible-light-driven oxidative coupling reactions of amines under an air atmosphere.

Chemoselective Ullmann Reaction of α-Trisubstituted Thioamides: Synthesis of Novel 2-Iminobenzothiolanes

New classes of unexplored benzo[b]thiolanes are synthesized from trisubstituted thioamides through copper-catalyzed intramolecular S-arylation of thioamides for the first time. This method provides good to excellent yields with fully controlled chemoselectivity. Unusually, iminobenzo[b]thiolanes are very stable under mild acidic conditions. A plausible mechanism is proposed for the chemoselective S-arylation process.

Tunable Trifunctionalization of Tertiary Enaminones for the Regioselective and Metal-Free Synthesis of Discrete and Proximal Phosphoryl Nitriles

This paper reports an unprecedented trifunctionalization of tertiary enaminones for the synthesis phosphoryl nitriles by the reactions of enaminones with diarylphosphine oxides and trimethylsilyl cyanide (TMSCN) without the use of any metal reagent. Employing tetrabutyl ammonium hydroxide (TBAH) as the catalyst (0.2 equiv) enables discrete cyanophosphonation. On the other hand, selective proximal cyanophosphonation has been realized in the presence of acetic acid only (AcOH).