Copper-catalyzed asymmetric sp³ C–H arylation of tetrahydroisoquinoline mediated by a visible light photoredox catalyst

• Pierre Querard,
• Inna Perepichka,
• Eli Zysman-Colman and
• Chao-Jun Li

Beilstein J. Org. Chem. 2016, 12, 2636–2643, doi:10.3762/bjoc.12.260

• , St Andrews, Fife, KY16 9ST, UK 10.3762/bjoc.12.260 Abstract This report describes a highly enantioselective oxidative sp3 C–H arylation of N-aryltetrahydroisoquinolines (THIQs) through a dual catalysis platform. The combination of the photoredox catalyst, [Ir(ppy)2(dtbbpy)]PF6, and chiral copper

• photoredox system might help, which indeed has improved the reaction yield and enantioselectivity. Different iridium and ruthenium photoredox catalysts were evaluated and [Ir(ppy)2(dtbbpy)]PF6 was found to be the most efficient [32]. With this iridium photoredox catalyst, TBHP, and copper(I) bromide co

• toluene and THF (Table 1, entries 7 and 8). On the other hand, highly polar solvents such as MeCN and MeOH were not beneficial for the formation of the desired product 3a (Table 1, entries 9 and 10). Control experiments performed in the absence of photoredox catalyst and/or transition metal copper(II

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• -aryltetrahydroisoquinolines with alkynes (Scheme 11) [33]. By using an iridium-based photoredox catalyst in combination with benzoyl peroxide, iminium ion 7 is formed in situ. This strategy enables reduction of the reaction temperature, ultimately enabling higher enantioselectivities. With respect to the scope of alkynes

Eosin Y-catalyzed visible-light-mediated aerobic oxidative cyclization of N,N-dimethylanilines with maleimides

• Zhongwei Liang,
• Song Xu,
• Wenyan Tian and
• Ronghua Zhang

Beilstein J. Org. Chem. 2015, 11, 425–430, doi:10.3762/bjoc.11.48

• presented the same reaction using [Ru(bpy)3]3+ as photoredox catalyst under irradiation with visible light next year [44]. Herein, we show an environmentally friendly aerobic oxidative cyclization methodology that avoids the use of metal catalysts and makes full use of air as oxidant. Results and Discussion

An improved procedure for the preparation of Ru(bpz)₃(PF₆)₂ via a high-yielding synthesis of 2,2’-bipyrazine

• Danielle M. Schultz,
• James W. Sawicki and
• Tehshik P. Yoon

Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9

• . Moreover, the yields on larger scales were unreliable, and work-up and purification of this inefficient coupling reaction proved difficult. Thus, in order to accelerate our investigations of complex 2 as a strongly oxidizing photoredox catalyst, we required a robust, high-yielding, and scalable synthesis

Visible-light-induced bromoetherification of alkenols for the synthesis of β-bromotetrahydrofurans and -tetrahydropyrans

• Run Lin,
• Hongnan Sun,
• Chao Yang,
• Youdong Yang,
• Xinxin Zhao and
• Wujiong Xia

Beilstein J. Org. Chem. 2015, 11, 31–36, doi:10.3762/bjoc.11.5

• reported that visible-light-induced photoredox catalysis could serve as a more environmental-friendly alternative reaction system to obtain Br2 in situ from CBr4, an oxidative quencher of photoredox catalyst [16][17][18][19][20][21][22]. Thus, as part of difunctionalization of alkenes, with our continuous

Visible light photoredox-catalyzed deoxygenation of alcohols

• Daniel Rackl,
• Viktor Kais,
• Peter Kreitmeier and
• Oliver Reiser

Beilstein J. Org. Chem. 2014, 10, 2157–2165, doi:10.3762/bjoc.10.223

• = 2-phenylpyridine) as photoredox catalyst (Scheme 1) [10]. This protocol is applicable to a broad range of alcohols. It also greatly advanced the quest to develop sustainable methods for the deoxygenation of alcohols. Yet, several redox steps, i.e., the stoichiometric transformation of

Cyclization–endoperoxidation cascade reactions of dienes mediated by a pyrylium photoredox catalyst

• Nathan J. Gesmundo and
• David A. Nicewicz

Beilstein J. Org. Chem. 2014, 10, 1272–1281, doi:10.3762/bjoc.10.128

Direct C–H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

• Ren Tomita,
• Yusuke Yasu,
• Takashi Koike and
• Munetaka Akita

Beilstein J. Org. Chem. 2014, 10, 1099–1106, doi:10.3762/bjoc.10.108

• examination of photocatalytic trifluoromethylation of 1,1-diphenylethene 2a with 1 equivalent of Umemoto’s reagent 1a in the presence of 5 mol % fac-Ir(ppy)3, a photoredox catalyst, and 2 equivalents of K2HPO4, a base, in [D6]-DMSO under visible light irradiation (blue LEDs: λmax = 425 nm) for 2 h. As a

• absence of photocatalyst (Table 1, entries 9 and 10), strongly supporting that the photoexcited species of the photoredox catalyst play key roles in the reaction. The scope and limitations of the present photocatalytic trifluoromethylation of alkenes are summarized in Table 2. 1,1-Diphenylethenes with

Visible-light photoredox catalysis enabled bromination of phenols and alkenes

• Yating Zhao,
• Zhe Li,
• Chao Yang,
• Run Lin and
• Wujiong Xia

Beilstein J. Org. Chem. 2014, 10, 622–627, doi:10.3762/bjoc.10.53

• of phenols and alkenes has been developed utilizing visible light-induced photoredox catalysis. The bromine was generated in situ from the oxidation of Br− by Ru(bpy)33+, both of which resulted from the oxidative quenching process. Keywords: alkenes; bromination; phenols; photoredox catalyst

• obtained in 78% yield (Table 1, entry 1), whereas 3-bromo-4-methoxyphenol was not observed. The optimization of the reaction conditions were conducted by screening selected solvents and the amount of the photoredox catalyst using 1a as the representative substrate. As can be seen in Table 1, the solvent

• . The stereochemistry of the bromofuran compound was determined by 2D NMR spectra. Conclusion In summary, we have developed a mild and operationally simple method for the in situ preparation of bromine utilizing a visible-light photoredox catalyst. The reaction proceeds with high chemical yield and

Regioselective 1,4-trifluoromethylation of α,β-unsaturated ketones via a S-(trifluoromethyl)diphenylsulfonium salts/copper system

• Satoshi Okusu,
• Yutaka Sugita,
• Etsuko Tokunaga and
• Norio Shibata

Beilstein J. Org. Chem. 2013, 9, 2189–2193, doi:10.3762/bjoc.9.257

• chalcones. During the preparation of this article, the Nicewicz group showed a single example of conjugate trifluoromethylation of chalcone with sodium trifluoromethanesulfinate salt in the presence of N-methyl-9-mesitylacridinium as a photoredox catalyst resulting in a low product yield of 31% as a mixture