Photocatalytic sequential C–H functionalization expediting acetoxymalonylation of imidazo heterocycles

• Deepak Singh,
• Shyamal Pramanik and
• Soumitra Maity

Beilstein J. Org. Chem. 2023, 19, 666–673, doi:10.3762/bjoc.19.48

• activation and functionalization of sp2 and sp3 C–H bonds via relay catalysis (Scheme 4). The relay can be divided into two cycles; the first cycle (cycle-1) deals with the C(sp2)–H functionalization at the C-3 position of the imidazo heterocycles, while the second cycle (cycle-2) is all about the C(sp3)–H

In silico rationalisation of selectivity and reactivity in Pd-catalysed C–H activation reactions

• Liwei Cao,
• Mikhail Kabeshov,
• Steven V. Ley and
• Alexei A. Lapkin

Beilstein J. Org. Chem. 2020, 16, 1465–1475, doi:10.3762/bjoc.16.122

• mild conditions [13]. In particular, reactions involving palladium-catalysed activation of sp2 or sp3 C–H bonds of arenes or alkanes have been extensively investigated due to their wide scope and functional group tolerance [14]. A number of different mechanisms are proposed in the literature

Recent advances on the transition-metal-catalyzed synthesis of imidazopyridines: an updated coverage

• Gagandeep Kour Reen,
• Ashok Kumar and
• Pratibha Sharma

Beilstein J. Org. Chem. 2019, 15, 1612–1704, doi:10.3762/bjoc.15.165

• well, giving the corresponding products in excellent yields. This protocol served as a novel route for the synthesis of imidazo[1,5-a]pyridines 37 via oxidative amination of sp3 C–H bonds in the aerial atmosphere. The reaction involved oxidative dehydrogenation of benzylamine intermediate 92 to form 93

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• reactions using traditional chemistry and organophotoredox synthesis can offer some interesting options as well. Wu et al. reported the alkylation of unfunctionalised allylic and benzylic sp3 C–H bonds by reaction with Michael acceptors, using blue LEDs and acridinium salts (Scheme 12) [55]. The main

• exact definition of a reaction employed in LSF, Jiang and co-workers have described a procedure that allows the enantioselective aerobic olefination of α-amino sp3 C–H bonds, using cooperative asymmetric and organocatalysed photoredox catalysis (Scheme 29) [73]. This may not allow for direct

Mechanochemical synthesis of small organic molecules

• Tapas Kumar Achar,
• Anima Bose and
• Prasenjit Mal

Beilstein J. Org. Chem. 2017, 13, 1907–1931, doi:10.3762/bjoc.13.186

•  11) using 2,3-dichloro-5,6-dicyanoquinone (DDQ) as an efficient oxidant [67]. Su and co-workers have also reported an asymmetric version of the CDC reaction between terminal alkynes and sp3 C–H bonds under high speed ball milling conditions [68]. Several optically active 1-alkynyl

• reaction under mechanomilling [67]. Asymmetric alkynylation of prochiral sp3 C–H bonds via CDC [68]. Fe(III)-catalyzed CDC coupling of 3-benzylindoles [69]. Mechanochemical synthesis of 3-vinylindoles and β,β-diindolylpropionates [70]. Mechanochemical C–N bond construction using anilines and arylboronic

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

• catalysts provide a mild and highly effective sp3 C–H asymmetric arylation of THIQs. Keywords: C–H arylation; copper catalyst; enantioselectivity; visible light; Introduction Functionalization of sp3 C–H bonds is a unique and powerful transformation in modern organic synthesis, which remains a challenging

• interest in terms of atom economy, nevertheless enantioselectivity is difficult to control due to often-required harsh reaction conditions. Therefore, the development of simple and facile processes to functionalize sp3 C–H bonds under mild conditions in the absence of directing groups is of great interest

• providing extremely important tools for potential transition-metal-catalyzed enantioselective reactions of sp3 C–H bonds, which could be carried out at low temperature and under mild reaction conditions [13][14]. We envisioned that combining photoredox catalysis with typical cross-coupling methods will

Synthesis of 2-oxindoles via 'transition-metal-free' intramolecular dehydrogenative coupling (IDC) of sp² C–H and sp³ C–H bonds

• Nivesh Kumar,
• Santanu Ghosh,
• Subhajit Bhunia and
• Alakesh Bisai

Beilstein J. Org. Chem. 2016, 12, 1153–1169, doi:10.3762/bjoc.12.111

Opportunities and challenges for direct C–H functionalization of piperazines

• Zhishi Ye,
• Kristen E. Gettys and
• Mingji Dai

Beilstein J. Org. Chem. 2016, 12, 702–715, doi:10.3762/bjoc.12.70

• -functionalization reaction of N-(2-pyridinyl)piperazines with carbon monoxide and terminal olefins (Figure 13) [52]. Their previous work on pyridinyl group-directed Rh-catalyzed carbonylation at sp3 C–H bonds adjacent to the nitrogen atom in other alkylamines such as pyrrolidine, piperidine, and

Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones

• Ping Qian,
• Bingnan Du,
• Wei Jiao,
• Haibo Mei,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32

• -initiated cyclization [30][31] and other radical reactions [32][33][34]. Due to their low polarity and high bond-dissociation energy, the functionalization of unactivated sp3 C–H bonds in simple alkanes remains as a challenging task. The direct cascade, 1,2-alkyarylation of alkenes to construct multi

• alkanes resulting in alkyl-substituted oxindoles (Scheme 1a) [43]. However, cyclization of N-allylbenzamides initiated by the functionalization of sp3 C–H bonds of simple alkanes remains unexplored. Very recently, our group developed a metal-free hydroxyalkylation-initiated radical six-membered

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

• dichloromethane. More recently, a Pd(OAc)2/NaNO3/O2 catalytic system was developed for acetoxylation of unactivated sp3-C–H bonds using the same directing groups [87]. Air or oxygen (1 atm) played a role of terminal oxidant and sodium nitrate was a redox co-catalyst; the reactions were performed in a AcOH/Ac2O

Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

• Jincan Zhao,
• Hong Fang,
• Jianlin Han and
• Yi Pan

Beilstein J. Org. Chem. 2013, 9, 1718–1723, doi:10.3762/bjoc.9.197

• excellent stereoselectivity, and only trans-isomers are obtained. Keywords: alkenylation; cycloalkanes; decarboxylative; Fe(acac)3; free radical; sp3 C–H bonds; Introduction Direct C–H functionalization has become one of the most useful and attractive tools in organic chemistry because it can construct

• ][68]. Our group was surprised to find that low-cost Fe(acac)3 could catalyze the direct alkenylation of cyclohexane sp3 C–H bonds by decarboxylative couplings with high efficiency. Results and Discussion We initiated our investigation by reacting cinnamic acid (1a, 0.3 mmol) with cyclohexane (2a, 2 mL

• product 3, Fe(II) and carbon dioxide. The Fe(III) catalyst is then reformed via DTBP oxidation [71]. Conclusion In conclusion, an efficient procedure for the Fe(acac)3-catalyzed direct alkenylation of sp3 C–H bonds of cycloalkanes with DTBP as an oxidant has been reported. This method provides a useful

Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

• Daisuke Hirose and
• Tsuyoshi Taniguchi

Beilstein J. Org. Chem. 2013, 9, 1713–1717, doi:10.3762/bjoc.9.196

• precursor of a 5-amino-1,4-diol, and the access from simple aliphatic alkenes in one step is unprecedented. The functionalization of unreactive sp3 C–H bonds using a radical 1,5-hydrogen shift is an old methodology compared with modern transition metal-catalyzed C–H activation reactions [25][26][27], but

Copper-catalyzed aerobic aliphatic C–H oxygenation with hydroperoxides

• Pei Chui Too,
• Ya Lin Tnay and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2013, 9, 1217–1225, doi:10.3762/bjoc.9.138

• radical; 1,5-H radical shift; hydroperoxides; molecular oxygen; Introduction Aliphatic sp3 C–H bonds are ubiquitous components in organic molecules but rather inert towards most of the chemical reactions. It thus remains as one of the most challenging topics in organic synthesis to develop catalytic

Arylglycine-derivative synthesis via oxidative sp³ C–H functionalization of α-amino esters

• Zhanwei Xu,
• Xiaoqiang Yu,
• Xiujuan Feng and
• Ming Bao

Beilstein J. Org. Chem. 2012, 8, 1564–1568, doi:10.3762/bjoc.8.178

• reported the copper-catalyzed oxidative coupling reaction of alkynes with tertiary amine N-oxides [15]. This new strategy for the direct functionalization of sp3 C–H bonds adjacent to a nitrogen atom, via tertiary amine N-oxide intermediates, was successfully applied to the coupling reaction of ethyl 2

• -(disubstituted amino)acetates with indoles to achieve indolylglycine derivatives (Scheme 2, reaction 1) [16]. In the course of our continuous research on the direct functionalization of sp3 C–H bonds, we found that this new strategy could also be applied to the coupling reaction of naphthols and phenols with

• reaction of 5 with 2-naphthol may have occurred to generate the coupling product 3a. The generated 3-chlorobenzoate anion acted as a proton acceptor. In conclusion, a new strategy for the functionalization of sp3 C–H bonds of amino esters was successfully applied to the coupling reaction of ethyl 2

C–H Functionalization

• Huw M. L. Davies

Beilstein J. Org. Chem. 2012, 8, 1552–1553, doi:10.3762/bjoc.8.176

• impact on the streamlined synthesis of important compounds for the pharmaceutical industry and materials science. The selective functionalization of sp3 C–H bonds is a more challenging proposition, but in recent years significant advances have been made to suggest that even these types of transformations

Recent advances in the gold-catalyzed additions to C–C multiple bonds

• He Huang,
• Yu Zhou and
• Hong Liu

Beilstein J. Org. Chem. 2011, 7, 897–936, doi:10.3762/bjoc.7.103