Photoinduced Disulfide-Catalyzed Intramolecular Anti-Markovnikov Hydroamination through in Situ N–S Species

Abstract

The photoinduced anti-Markovnikov hydroamination of olefins typically required photocatalysts with a high oxidative ability to initiate the single-electron process. Herein, we alternatively utilize bis­(2,4,6-triisopropylphenyl) disulfide, an inexpensive reagent with relatively low oxidative ability, as a photo and hydrogen atom transfer catalyst to achieve intramolecular hydroamination. The mechanistic studies as well as the DFT calculations are consistent with a novel process involving N-centered radical generation through the homolysis of the in situ formed N–S species and subsequent cyclization. An array of diverse nitrogen-containing cycles could be obtained.

General Anti-Markovnikov Hydrophosphinylation of Olefins Using Disulfide as the Photocatalyst and a Hydrogen Atom Shuttle

“…Given that the disulfide could undergo homolysis under irradiation or react with the X−H bond to form X−S species and ArS−H through the photoinduced σ-metathesis, 15 an arisen concern is if the P−S species was formed in situ to undergo the subsequent homolysis? The reaction of 1a and 2a was conducted by using 1.0 equiv of (TRIPS) 2 under irradiation.…”

“…The P−S species TRIPS-P(O) might be the resting species, which was very different from the ready homolysis of the N−S species. 15 In addition, the yields could be increased to 20%, 37%, and 42% by adding 20 mol %, 50 mol %, and 100 mol % of TRIPSH, respectively, suggesting that TRIPSH might act as a hydrogen donor to promote the reaction.On the other hand, when the reaction of 1a and 2a was conducted at 100 °C to facilitate the thermal instead of the photoinduced homolysis of (TRIPS) 2 , the desired product was also able to obtain in 33% yield (eq 7),…”

“…However, when such a P–S species TRIPS-P­(O) was used as catalyst to facilitate the reaction of 1a and 2a , the desired product 3g was only isolated in 13% yield (eq 6 ), leading us to the conclusion that the homolysis of the P–S species might happen under the irradiation; however, this pathway might not be the major one in the catalytic cycle due to the relatively lower efficiency. The P–S species TRIPS-P­(O) might be the resting species, which was very different from the ready homolysis of the N–S species . In addition, the yields could be increased to 20%, 37%, and 42% by adding 20 mol %, 50 mol %, and 100 mol % of TRIPSH, respectively, suggesting that TRIPSH might act as a hydrogen donor to promote the reaction. On the other hand, when the reaction of 1a and 2a was conducted at 100 °C to facilitate the thermal instead of the photoinduced homolysis of (TRIPS) 2 , the desired product was also able to obtain in 33% yield (eq ), indicating that the TRIPS radical was crucial for the formation of the desired product.…”

“…On the basis of these investigations, a mechanism was proposed (Scheme ). First, the (TRIPS) 2 could be excited under the irradiation of 390 nm LEDs to undergo homolysis and produce ArS• properly. , The hydrogen atom abstraction from 2a occurred favorably to genreate the P-centered radical A , which underwent the intermolecular radical addition to obtain the C radical B . Finally, the fast HAT with ArSH would yield the product, regenerate the catalyst, and close the catalytic cycle.…”

Photoinduced Copper-Catalyzed Aminoalkylation of Amino-Pendant Olefins

“…In the exo-cyclizationoriented difunctionalization of amino-pendant olefins, amination is facilitated potently within the molecule. 7 Besides, amination can be realized along with the introduction of foreign components for further halogenation, acylation, fluorosulfonylation, oxy-acetoxylation, oxyamination, hydroxylation, methoxylation, diazotization, trifluoromethylation, cyanation, arylation, alkynylation, etc. 8 The robust and straightforward strategies for the above transformations can be broken into five main categories: (1) transition metal catalysis; 8a,b (2) oxidation with a stoichiometric oxidant; 8c (3) photoredox catalysis combining an organic photocatalyst with a stoichiometric base; 8d−h (4) cooperative photoredox/ transition metal dual catalysis; 8i,j and (5) electrochemical method 8k,l (Scheme 1b, condition C).…”