Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• ], electron-deficient arenes [24], and nitriles [25]. Additionally, Cozzi recently applied a novel aluminium-based photocatalyst 9 to this reaction, as an earth-abundant metal alternative albeit with slightly reduced enantioselectivities (8 examples, up to 96:4 er) [26]. Interestingly, as with some other

• the [2 + 2] photocycloaddition of 2-pyridones 186 and acetylenedicarboxylates 187 catalysed by ent-183 to give cyclobutenes 188 (Scheme 28b) [82]. Another intermolecular reaction was later developed, this time using catalyst 185 for the [2 + 2] photocycloaddition of quinolones 189 and electron

• -deficient alkenes 190 to synthesise cyclobutanes 191 (Scheme 28c) [83]. Recently, Bach et al. also employed this methodology for the intramolecular [2 + 2] cycloaddition of quinolones 192 containing either a pendant alkene or allene to obtain cyclobutanes 193 (Scheme 28d) [84]. Recently, ent-185 was applied

Design and synthesis of a bis-macrocyclic host and guests as building blocks for small molecular knots

• Elizabeth A. Margolis,
• Rebecca J. Keyes,
• Stephen D. Lockey IV and
• Edward E. Fenlon

Beilstein J. Org. Chem. 2020, 16, 2314–2321, doi:10.3762/bjoc.16.192

• molecular knots. The modular second-generation approach to small trefoil knots described herein involves electrostatic interactions between an electron-rich bis-macrocyclic host compound and electron-deficient guests in the threading step. The bis-macrocyclic host was synthesized in eight steps and 6.6

• ]. Herein the synthesis of a unique bis-macrocyclic host 1 is described (Figure 1). Host 1 was designed to be a second-generation building block in the thread–link–cut (TLC) approach to molecular knots [13]. The two 25-atom macrocycles are electron-rich and complementary to the electron-deficient guests bis

Chan–Evans–Lam N1-(het)arylation and N1-alkеnylation of 4-fluoroalkylpyrimidin-2(1H)-ones

• Viktor M. Tkachuk,
• Oleh O. Lukianov,
• Mykhailo V. Vovk,
• Isabelle Gillaizeau and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2020, 16, 2304–2313, doi:10.3762/bjoc.16.191

• substituents (a methoxy or 1-pyrrolidinyl group) at position 4 of 3-pyridylboronic acid enabled increased yields of the target products 3s and 3t thus opening a preparative pathway to a wide variety of 4-alkoxy-3-pyridyl and 4-dialkylamino-3-pyridyl derivatives. Hetarylboronic acids containing a more electron

• -deficient pyrimidyl instead of the pyridyl residue was completely unreactive to N1-hetarylation of substrate 1a under the conditions used. Contrary to this case, the method developed allowed electron-rich heterocyclic nuclei including the 3-thienyl (but not isomeric 2-thienyl), 5-trifluoromethyl-3-thienyl

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• Asitanga Ghosh Deptartment of Chemistry, Hooghly Mohsin College, Chinsurah, Hooghly, West Bengal, 712101, India 10.3762/bjoc.16.190 Abstract Photochemical reactions of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores like a 5,6 dibenzoyl moiety and bulky electron-deficient substituents

• photoproduct 6g was obtained when 3g was irradiated [10]. In all of the molecules, the bridgehead positions contain only electron-donor groups (such as OMe, Me, etc.), but same type of rigid enones having electron deficient groups at the bridgehead positions have not been checked so far. To bridge this gap, we

• under similar reaction conditions, a mixture of methyl esters 11a and 11b was obtained in the same 1:6 ratio with a moderate yield (60%). Conclusion From the above results it was evident that the presence of phenyl or isopropenyl like electron-deficient bulky substituents at the bridgehead position of

Regioselective cobalt(II)-catalyzed [2 + 3] cycloaddition reaction of fluoroalkylated alkynes with 2-formylphenylboronic acids: easy access to 2-fluoroalkylated indenols

• Tatsuya Kumon,
• Miroku Shimada,
• Jianyan Wu,
• Shigeyuki Yamada and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 2193–2200, doi:10.3762/bjoc.16.184

• substituted 2-formylphenylboronic acids 2. Electron-deficient formylphenylboronic acids possessing a fluorine or chlorine atom on the benzene ring gave the corresponding indenols 3aB and 3aC in 41% and 32% yield, respectively, which could not be improved even when an excess loading of the reagents, prolonging

Efficient [(NHC)Au(NTf₂)]-catalyzed hydrohydrazidation of terminal and internal alkynes

• Maximillian Heidrich and
• Herbert Plenio

Beilstein J. Org. Chem. 2020, 16, 2080–2086, doi:10.3762/bjoc.16.175

• effect was weaker, but nonetheless the conversion of the electron-deficient hydrazides (R = NO2) was slightly more efficient than with the electron-rich hydrazides (R = NMe2). Conclusion In conclusion, we have demonstrated the efficient hydrohydrazidation of various terminal and internal alkynes

Natural dolomitic limestone-catalyzed synthesis of benzimidazoles, dihydropyrimidinones, and highly substituted pyridines under ultrasound irradiation

• Kumar Godugu,
• Venkata Divya Sri Yadala,
• Mohammad Khaja Mohinuddin Pinjari,
• Trivikram Reddy Gundala,
• Lakshmi Reddy Sanapareddy and
• Chinna Gangi Reddy Nallagondu

Beilstein J. Org. Chem. 2020, 16, 1881–1900, doi:10.3762/bjoc.16.156

• , with good yields of 7k (90%) and 7l (92%), respectively (Table 6, entries 11 and 12). From this study, it was concluded that the optimized reaction conditions are suitable for monosubstituted (both electron-rich and electron-deficient) and disubstituted benzaldehyde derivatives as well as

One-pot and metal-free synthesis of 3-arylated-4-nitrophenols via polyfunctionalized cyclohexanones from β-nitrostyrenes

• Haruyasu Asahara,
• Minami Hiraishi and
• Nagatoshi Nishiwaki

Beilstein J. Org. Chem. 2020, 16, 1830–1836, doi:10.3762/bjoc.16.150

• method toward the preparation of 3-arylated-4-nitrophenols. On the other hand, nitroalkenes possess an electron-deficient double bond, and hence, they serve as an excellent Michael acceptor and dienophile [12][13][14][15][16][17][18][19]. When β-nitrostyrene (1, Ar = Ph) is subjected to the Diels–Alder

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

• , pyrimidines, and oximes (Figure 20). The mild arylation proceeded in good to excellent yields over 20 examples and worked with electron-deficient, electron-rich as well as relatively sterically hindered arylating reagents. The mechanism proposed by the authors is presented in Figure 21. First, the DG-assisted

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• the intramolecular version, the fluorine atom or fluorinated group can also form a part of the linker. The reaction yields are dependent on the degree of substitution, bulkiness, and electronic effects of the substituents of both the alkyne and alkene moieties. In general, electron-deficient alkynes

Photoredox-catalyzed silyldifluoromethylation of silyl enol ethers

• Vyacheslav I. Supranovich,
• Vitalij V. Levin and
• Alexander D. Dilman

Beilstein J. Org. Chem. 2020, 16, 1550–1553, doi:10.3762/bjoc.16.126

• silane is very sensitive to Lewis bases and accordingly it was used as a precursor of difluorocarbene, which can react with enol ethers [19][20] (Scheme 1). We showed that this silane could be involved in the radical chain hydrofluoroalkylation of electron-deficient alkenes, using a boron hydride as a

One-pot synthesis of 1,3,5-triazine-2,4-dithione derivatives via three-component reactions

• Gui-Feng Kang and
• Gang Zhang

Beilstein J. Org. Chem. 2020, 16, 1447–1455, doi:10.3762/bjoc.16.120

• reaction, and provided products 6ga and 6ha in still moderate yields. When an electron-deficient aromatic aldehyde such as 4-phenylbenzaldehyde (1i) was used, the reaction effectively afforded product 6ia in 45% yield. Similarly, benzaldehydes having other electron-withdrawing groups such as cyano, nitro

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• thietanes. Later, this transformation was considered as thia-Paternò–Büchi reaction. The reactions of thiobenzophenone (184a) with both, electron-rich olefins 185, 186a, and 187a under irradiation with UV light at 366 nm, and electron-deficient olefins 187b,c, 188, and 189 under irradiation with either 366

• of electron-deficient olefins 187b,c, 189, 242a, and 269–272. The reactions afforded stereospecifically and regioselectively the 3-functionalized spirothietanes 273–285 as the major products. The stereospecific addition suggested either a concerted process or a pathway involving very short-lived

• functionalized thietanes, electron-deficient sulfur ylides were investigated in the ring expansion of thiiranes. However, the reactions failed due to the poor nucleophilicity of the electron-deficient sulfur ylides. However, in the presence of rhodium catalysts, the electron-deficient sulfur ylides were

Ferrocenyl-substituted tetrahydrothiophenes via formal [3 + 2]-cycloaddition reactions of ferrocenyl thioketones with donor–acceptor cyclopropanes

• Grzegorz Mlostoń,
• Mateusz Kowalczyk,
• André U. Augustin,
• Peter G. Jones and
• Daniel B. Werz

Beilstein J. Org. Chem. 2020, 16, 1288–1295, doi:10.3762/bjoc.16.109

• -methanides (thiocarbonyl ylides) with electron-deficient ethylenic dipolarophiles. This method was extensively developed by Huisgen and co-workers in the 1980s [3][4][5]. In the course of these studies, a non-orthodox stepwise mechanism of the 1,3-dipolar cycloaddition was established by experiments

• performed with the sterically crowded thiocarbonyl S-methanide 1, derived from 2,2,4,4-tetramethyl-3-thioxocyclobutanone and extremely electron-deficient ethylenes 2 such as (E)- and (Z)-dialkyl dicyanobutenoates (R = CO2Me) [6], tetracyanoethylene (R = CN) [7] or (E)- and (Z)-1,2-bis(trifluoromethyl

• molecular structures of cis-9c and trans-9d drawn using 50% probability displacement ellipsoids. The terminology cis and trans referred to the relative orientation of Ph and Fc groups. Synthesis of spirotetrahydrothiophenes 3 via non-concerted [3 + 2]-cycloadditions of thiocarbonyl ylide 1 with electron

Photocatalysis with organic dyes: facile access to reactive intermediates for synthesis

• Stephanie G. E. Amos,
• Marion Garreau,
• Luca Buzzetti and
• Jerome Waser

Beilstein J. Org. Chem. 2020, 16, 1163–1187, doi:10.3762/bjoc.16.103

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

• Shigeyuki Yamada,
• Takuya Higashida,
• Yizhou Wang,
• Masato Morita,
• Takuya Hosokai,
• Kaveendra Maduwantha,
• Kaveenga Rasika Koswattage and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 1154–1162, doi:10.3762/bjoc.16.102

• proposed mechanism of Pd(II)-catalyzed C≡C oxidation is illustrated in Scheme 2 [33]: The catalytic cycle starts with the coordination of the electron-rich C≡C bond to the electron-deficient divalent Pd center, forming the corresponding π-complex (Int-A). Int-A smoothly undergoes nucleophilic attack by the

• proposed reaction mechanism, the successful isolation of the half-oxidized benzil derivatives 2a and 2b from the oxidation of fluorinated bistolanes 1a and 1b, respectively, may be due to the decreased reactivity of the C≡C bond toward Pd(II)-catalyzed C≡C oxidation caused by the adjacent electron

• -deficient fluorinated aromatic ring. To confirm the electron-withdrawing effect of this fluorinated aromatic ring, the electronic charge at the adjacent C≡C bond was calculated by density functional theory (DFT) using the Gaussian 16 (Revision B.01) software package [35]. As typical examples, the molecular

Accelerating fragment-based library generation by coupling high-performance photoreactors with benchtop analysis

• Quentin Lefebvre,
• Christophe Salomé and
• Thomas C. Fessard

Beilstein J. Org. Chem. 2020, 16, 982–988, doi:10.3762/bjoc.16.87

• reactions, and ranged from 6% to 50% for copper-catalyzed cross-coupling reactions [13]. Much information could be obtained from this screening. Electron-deficient aryl bromides led to better yields than neutral and electron-rich partners, as observed in previous reports on photochemically- or

• electrochemically-mediated nickel-catalyzed cross-couplings. Electron-deficient aniline products are less prone to oxidative decomposition. BCP-amines were viable coupling partners but gave the corresponding products 1a–e in poor purities. Simple azetidines partook the reaction to give 2a–c while azaspiro[3,3

Pd-catalyzed asymmetric Suzuki–Miyaura coupling reactions for the synthesis of chiral biaryl compounds with a large steric substituent at the 2-position

• Yongsu Li,
• Bendu Pan,
• Xuefeng He,
• Wang Xia,
• Yaqi Zhang,
• Hao Liang,
• Chitreddy V. Subba Reddy,
• Rihui Cao and
• Liqin Qiu

Beilstein J. Org. Chem. 2020, 16, 966–973, doi:10.3762/bjoc.16.85

• 3d). The yield and ee value of an oxazolidinone amide were slightly lower than those of tetrahydropyrrolamide (3e, 3f). Various aromatic substituted amides were investigated. The results show that electron-rich or electron-deficient substituents on the phenyl ring have no significant influence on the

• enantiomeric excesses of the products (3g–n), but the best ee value was obtained for the substrate with an electron-deficient phenyl ester (88% ee, 3o). By changing 1-naphthaleneboronic acid to 4-substituted-1-naphthaleneboronic acids 3p, 3q and 3r, the enantioselectivity and the yield of the reaction

• heterocyclic group, an electron-rich aromatic or an electron-deficient aromatic group, the reaction always performed well with high yield and good enantioselectivity. We guess that the large sterically hindered π-plane formed between a carbonyl group and a benzene ring is the guarantee of high ee values of the

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• applications of these compounds in photomedicine [23][25][26][27]. Recently we reported a porphyrin-photocatalyzed protocol for the arylation of enol acetates and elucidated the mechanism explaining why the electron-deficient porphyrin TPFPP is more efficient than TPP in the whole process (Scheme 4A). Briefly

• -rich and electron-deficient groups in the arylsulfinic acid and alkyl sulfinates, such as sodium ethylsulfinate and sodium methylsulfinate (Scheme 19). The authors also showed that the methodology can be applied to the sulfonation of steroid drug arimistane in 45% yield (Scheme 20). The mechanistic

• epoxidation agent of an electron-deficient olefin intermediate, which was formed by deaminative Mannich coupling between the imine and nucleophiles such as malononitrile and methyl cyanoacetate (Scheme 64) [109]. Overall, a variety of additional examples of porphyrin-photocatalyzed heteroatom oxidations are

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• rearrangements, are frequently observed [8]. The use of oxidative couplings is further limited for the synthesis of strained [9][10], electron-deficient, or sterically congested aromatics [11][12][13][14]. Some of these limitations can be overcome by using prefunctionalized precursors [11], as exemplified by

• materials, this strategy has so far remained relatively unexplored [27]. As a part of our ongoing research on π-extended electron-deficient oligopyrroles [13][28][29][30][31], we have recently reported that Pd(II)-mediated double C–H activation can be a useful tool for conversion of 1,n-dipyrrolylalkanes

• into boomerang-shaped N,N'-bridged α,α'-bipyrroles that are not accessible by means of conventional oxidative coupling methods (Scheme 1) [32]. Our approach is applicable to electron-deficient and sterically encumbered systems, notably those based on pyrrole derivatives fused with naphthalenediamide

Towards triptycene functionalization and triptycene-linked porphyrin arrays

• Gemma M. Locke,
• Keith J. Flanagan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70

• significantly more enhanced, in comparison to the practically quenched fluorescence detected for the zinc-nickel dimer 16 which may be due to the electron-deficient nature of the nickel porphyrin [47]. In this instance, the excited zinc porphyrin is acting as electron donor while the electronically inactive

Cascade trifluoromethylthiolation and cyclization of N-[(3-aryl)propioloyl]indoles

• Ming-Xi Bi,
• Shuai Liu,
• Yangen Huang,
• Xiu-Hua Xu and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2020, 16, 657–662, doi:10.3762/bjoc.16.62

• bearing an alkyl or electron-deficient aryl substituent on the alkynone were not successful. The structure of product 2a was unambiguously identified by single-crystal X-ray analysis. When the N-[(3-aryl)propioloyl]indole substrates (3a–d) with different substituents at the 3-position of the indole ring

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• as gold catalysts (e.g., gold(I) cyanide), solvents (e.g., CH2Cl2, THF, MeCN, DMF), additives (e.g., TFA, Sc(OTf)3), and temperature, the reaction conditions as mentioned earlier were chosen for the synthesis of 5a and 6a (Table S1, Supporting Information File 1). Because of the electron-deficient

• are significantly shifted in the anodic direction rather than the extent of the shifts in the oxidation potentials [30]. The electron-deficient effect of the substituents is pronounced for the doubly substituted derivatives 4a and 6a. Consequently, the electrochemical energy gaps of 3a–6a are

A systematic review on silica-, carbon-, and magnetic materials-supported copper species as efficient heterogeneous nanocatalysts in “click” reactions

• Pezhman Shiri and
• Jasem Aboonajmi

Beilstein J. Org. Chem. 2020, 16, 551–586, doi:10.3762/bjoc.16.52

• multitriazole products in polyethylene glycol as a green solvent at room temperature (Scheme 10). The authors proposed that sodium ʟ-ascorbate acted as a reducing agent in the reduction of Cu(II) to Cu(I). Aromatic/aliphatic terminal acetylenes and benzyl bromides bearing electron-rich and electron-deficient

Controlling alkyne reactivity by means of a copper-catalyzed radical reaction system for the synthesis of functionalized quaternary carbons

• Goki Hirata,
• Yu Yamane,
• Naoya Tsubaki,
• Reina Hara and
• Takashi Nishikata

Beilstein J. Org. Chem. 2020, 16, 502–508, doi:10.3762/bjoc.16.45

• the reaction of 2a and electron-deficient alkyne 4a was performed under the conditions shown in Table 1, entry 9, the C–H cyclized product 5a was obtained instead of 3k. In this case, an alkyl radical addition followed by C–H cyclization via an alkenyl radical intermediate could be occur (Scheme 4). A