Recent advances in transition-metal-catalyzed incorporation of fluorine-containing groups

• Xiaowei Li,
• Xiaolin Shi,
• Xiangqian Li and
• Dayong Shi

Beilstein J. Org. Chem. 2019, 15, 2213–2270, doi:10.3762/bjoc.15.218

Hydroarylations by cobalt-catalyzed C–H activation

• Rajagopal Santhoshkumar and
• Chien-Hong Cheng

Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202

• site selectivity. The found inter- and intramolecular KIEs (kH/kD) of 1.4 shows that the C−H activation may not be the rate the determining step. Moreover, competition experiments indicate that the reaction favors electron-rich arenes 64 and electron-deficient isocyanates. Ellman’s group also reported

Cobalt bis(acetylacetonate)–tert-butyl hydroperoxide–triethylsilane: a general reagent combination for the Markovnikov-selective hydrofunctionalization of alkenes by hydrogen atom transfer

• Xiaoshen Ma and
• Seth B. Herzon

Beilstein J. Org. Chem. 2018, 14, 2259–2265, doi:10.3762/bjoc.14.201

• alkene scope and exploring the site-selectivity in polyene substrates. General mechanism of alkene hydrofunctionalization via HAT. Reduction of the alkenyl chloride 1 by HAT. Substrate scope of alkyl-aryl azo compound synthesis via HAT. Conditions: alkene (0.250 mmol), diazonium salt (1.50 equiv), Co

Bromide-assisted chemoselective Heck reaction of 3-bromoindazoles under high-speed ball-milling conditions: synthesis of axitinib

• Jingbo Yu,
• Zikun Hong,
• Xinjie Yang,
• Yu Jiang,
• Zhijiang Jiang and
• Weike Su

Beilstein J. Org. Chem. 2018, 14, 786–795, doi:10.3762/bjoc.14.66

• yields (88–96%) and excellent selectivity (the dehalogenated side-product 4 was not detected in most cases). Among which, strong electron-withdrawing substrates required long reaction times to achieve the desired results (3ca, 3ga, 3pn). It was suprising to find that substrate 1d showed excellent site

• -selectivity under 700 rpm, giving 6-bromo-substituted product 3da in 94% yield. Indazoles with N-Me, THP and Bn groups afforded good to excellent yields in the coupling reaction with n-butyl acrylate. However, the N-Boc substrate readily underwent removal of the protecting group [65], and resulted in the

Synthesis of β-arylated alkylamides via Pd-catalyzed one-pot installation of a directing group and C(sp³)–H arylation

• Yunyun Liu,
• Yi Zhang,
• Xiaoji Cao and
• Jie-Ping Wan

Beilstein J. Org. Chem. 2016, 12, 1122–1126, doi:10.3762/bjoc.12.108

• incorporation of a metal catalyst and controlling the site selectivity [7][8][9]. While benefiting the advantage of straightforward transformation from the C–H activation strategy, the utilization of a DG also brings unfavorable defection of step economics because an additional operation step in installing the

Recent advances in C(sp³)–H bond functionalization via metal–carbene insertions

• Bo Wang,
• Di Qiu,
• Yan Zhang and
• Jianbo Wang

Beilstein J. Org. Chem. 2016, 12, 796–804, doi:10.3762/bjoc.12.78

• –carbene; site-selectivity; Introduction Direct functionalization of inactivated C–H bonds, especially C(sp3)–H bonds, have attracted significant attentions in recent years. The C(sp3)–H bond activation strategies based on radical reactions and transition metal catalysis have been explored, alongside the

• development of various directing groups for controlling the site-selectivity of the reaction. Regardless of the great efforts devoted to the field, the intermolecular C(sp3)–H bond activation of simple alkanes still remains a formidable challenge, obviously attributed to the inertness and ubiquitous nature of

• site-selectivity of C(sp3)–H bond insertion is also affected by steric factors. High regioselectivity of C(sp3)–H bond insertions has been observed in intramolecular reactions in most cases, in which the C(sp3)–H bond positioned 5 atoms away from the carbene center will normally react preferentially

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• electron-enriched arenes [7][8][9], diazotization/halogenations of anilines [10], and ortho-lithiation/halogenations sequence [11] among others are widely used as traditional strategies for creating C–X bonds. However, one or more problems such as poor site-selectivity, reliance on toxic halogen sources

• the conventional electrophilic halogenation of arenes, the site selectivity was a main challenge and mixed haloarene products were frequently obtained. In 2006, Yu and co-workers [32] first realized the selective o-halogenation of pyridine-2-ylbenzenes 1 via C–H activation in a copper/O2 system. As

• shown in Scheme 1, the presence of the pyridine ring was crucial in controlling the site selectivity by forming the copper complex 3 which enabled the selective halogenation of the ortho C–H bond of the phenyl ring to give products 2 via transition state 4 and 5. The 1,1,2,2-tetrahaloethane played the

Site-selective covalent functionalization at interior carbon atoms and on the rim of circumtrindene, a C₃₆H₁₂ open geodesic polyarene

• Hee Yeon Cho,
• Ronald B. M. Ansems and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2014, 10, 956–968, doi:10.3762/bjoc.10.94

• , optical, magnetic, mechanical, and chemical properties of the material. For such functionalization reactions, site selectivity often becomes an issue when there is more than one site where the reaction could occur. Herein, we report methods for the site-selective covalent functionalization of

• –Hirsch reaction proceeds smoothly to afford 20 in good yield and with complete site selectivity (Scheme 5). The reaction was performed with five equivalents of bromomalonate and one equivalent of DBU (1,8-diazabicyclo[5.4.0]undec-7-ene) as a base in toluene at room temperature. Based on mechanism studies

• curvature on the convex surface (i.e., the carbon atoms with the greatest POAV angle, see Figure 5). Similar site selectivity for the 6:6-bond that incorporates the most pyramidalized carbon atoms has previously been observed in the functionalization of fullerene C70 [56]. As explained in the introductory

Mechanistic studies on the CAN-mediated intramolecular cyclization of δ-aryl-β-dicarbonyl compounds

• Brian M. Casey,
• Dhandapani V. Sadasivam and
• Robert A. Flowers II

Beilstein J. Org. Chem. 2013, 9, 1472–1479, doi:10.3762/bjoc.9.167

• radical intermediates. Furthermore, DFT computational studies were used to rationalize the observed site selectivity in the 2-tetralone products. Keywords: CAN oxidation; β-dicarbonyls; free radical; radical arylations; tetralones; Introduction 2-Tetralones are important intermediates or components of

• as single isomers. Moreover, the isomers formed from these reactions result from cyclization occurring at the more hindered carbon atom of the δ-aryl ring. This observed site selectivity is consistent with previous research by both MacMillan and Nicolaou on the α-arylation of aldehydes through organo

• compared to the parent aryl diketone radical, and the rotational transition structure has a comparable barrier of 2.5 kcal/mol. While it is evident why electron-rich systems should more readily cyclize, the observed site selectivity in products 2g and 2j warranted further investigation. For these

C–H Functionalization

• Huw M. L. Davies

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

• functionalization of complex systems at will. To achieve this, it will be necessary to have an extensive toolbox of catalysts and reagents to override the natural site selectivity of any given substrate. Therefore, a greater range of reaction types need to be developed and a better mechanistic understanding of the

Electronic differentiation competes with transition state sensitivity in palladium- catalyzed allylic substitutions

• Dominik A. Lange and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2007, 3, No. 36, doi:10.1186/1860-5397-3-36

• phospha-benzene-pyridine ligands. Although donor/acceptor substitutions at P and N ligand sites were expected to increase the site selectivity, i.e. the preference for "trans to P" attack at the allylic intermediate, acceptor/acceptor substitution yields the highest selectivity. Energetic and geometrical

• analyses of transition structures show that the sensitivity for electronic differentiation is crucial for this site selectivity. Early transition structures with acceptor substituted ligands give rise to more intensive Pd-allyl interactions, which transfer electronic P,N differentiation of the ligand more

• -memory effects. [42][43] Computational model systems for P,N-ligands, i.e. PH3 and para-substituted pyridines, have shown that cis-trans differentiations, i.e. the electronic site selectivity, of nucleophilic additions to Pd-η3-allylic intermediates is highest for electron poor pyridine ligands.[45] To