Reactions of 3-aryl-1-(trifluoromethyl)prop-2-yn-1-iminium salts with 1,3-dienes and styrenes

• Thomas Schneider,
• Michael Keim,
• Bianca Seitz and
• Gerhard Maas

Beilstein J. Org. Chem. 2020, 16, 2064–2072, doi:10.3762/bjoc.16.173

• consider the reactivity of the electrophilic (“electron-poor”) acetylenic bond toward 1,3-dienes, and show how the expected [4 + 2] or [2 + 2] cycloaddition products can enter subsequent cascade reactions toward carbocycles which incorporate a C(CF3)NMe2 structural unit. Results and Discussion The Diels

• presumably renders an ionic [2 + 2] cycloaddition pathway competitive with the Diels–Alder reaction. The few reported examples of cyclobutene formation from alkynes and unactivated 1,3-dienes include the sensitized photocycloaddition of phenylacetylene and DMBD [30] and the gold(I)-catalyzed reaction of

• -substituted iminium groups with electron-rich (hetero)aromatics are known [18][24]. Furthermore, 1-(trifluoromethyl)indenes have recently been generated by cationic cyclization of β-aryl trifluoromethyl enones under superacid conditions [42][43][44]. Styrenes are also known to behave as dienes in [4 + 2

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

• an aromatic unit in α-position to the nitrogen atom. Sensitive functional groups such as hydroxy, silyl, and ethynyl were tolerated by this protocol. Furthermore, this methodology was also extended towards the C–H annulation with dienes. The proposed mechanism of this reaction requiring only oxygen

An overview on disulfide-catalyzed and -cocatalyzed photoreactions

• Yeersen Patehebieke

Beilstein J. Org. Chem. 2020, 16, 1418–1435, doi:10.3762/bjoc.16.118

• benzyloxymethylenetriphenylphosphane to give the dienes 71 and 72 as a 3:1 mixture. At room temperature, the resulting (E,E)-isomer 71 is quantitatively converted into the desired oxatricyclic system 74 via a diastereoselective Diels–Alder cycloaddition process. However, the (Z,E)-isomer 72 remains unreactive under these reaction

Highly selective Diels–Alder and Heck arylation reactions in a divergent synthesis of isoindolo- and pyrrolo-fused polycyclic indoles from 2-formylpyrrole

• Carlos H. Escalante,
• Eder I. Martínez-Mora,
• Carlos Espinoza-Hicks,
• Alejandro A. Camacho-Dávila,
• Fernando R. Ramos-Morales,
• Francisco Delgado and
• Joaquín Tamariz

Beilstein J. Org. Chem. 2020, 16, 1320–1334, doi:10.3762/bjoc.16.113

• -vinylpyrroles 16a,b were chosen as the dienes to evaluate the reactivity with diverse dienophiles. The reaction of acrolein, methyl acrylate, maleic anhydride and maleimide (R3 = H, 7a) in xylene by heating up to 150 °C failed to provide the corresponding adducts. It was possible to recover the starting

• ratio determined through the Gibbs energy (endo/exo, 79.9:20.1) matched better. Actually, the reactivity of diene 8b would be expected to be lower due to a greater deactivation of the cyano group, as suggested by comparing the most stable HOMO of this diene with the values for dienes 8c and 8g

• (Supporting Information File 1, Table S1). Hence, the latter dienes should be more reactive than diene 8b, and consequently more stereoselective [54][55][56]. In contrast, the Gibbs energy for the diene/dienophile 8c/7b (88.8:11.2) did not completely match the experimental endo/exo (99:1) ratio, but the ZPE

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

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

• pericyclic reactions with olefins and dienes, and the second deals with heteroatom oxidations carried out by singlet oxygen. Review Porphyrins as photoredox catalysts Porphyrins and metalloporphyrins have been extensively studied as photosensitizers in singlet oxygen generation, but underexploited as

• (1Δg) the main photoactive species in solution [63][64][65]. Singlet oxygen is a highly reactive electrophile toward electron-rich organic molecules/atoms such as alkenes, dienes, and heteroatoms (N, P, S, Se, etc.) making this molecule very effective in pericyclic reactions and heteroatom oxidations

• improved protocol when using continuous conditions. Subsequently, we reported a comprehensive methodology involving photooxygenations of conjugated dienes and rearrangements, thus leading to relevant oxidized products (Scheme 37) [87]. In this methodology, we developed in both batch and continuous-flow

Diversity-oriented synthesis of 17-spirosteroids

• Benjamin Laroche,
• Thomas Bouvarel,
• Martin Louis-Sylvestre and
• Bastien Nay

Beilstein J. Org. Chem. 2020, 16, 880–887, doi:10.3762/bjoc.16.79

• study (Scheme 2). Thus, in the presence of G-II in toluene and under microwave heating, the reaction provided 17-spirosteroid dienes 8–10 in good yields (67–82%). Spirocyclic vinylcyclopentene substrates 8a,b and 9a,b were engaged in Diels–Alder reactions with a variety of dienophiles (11–15). The

• 84% yield. Concerning the use of oxepane-type dienes 8b and 9b, none of the attempted Diels–Alder reactions proved efficient, systematically leading to a mixture of diastereoisomers and difficult purifications. Only cycloadducts 16f and 17b could be isolated in minute amounts (Scheme 3). Finally, the

Copper catalysis with redox-active ligands

• Agnideep Das,
• Yufeng Ren,
• Cheriehan Hessin and
• Marine Desage-El Murr

Beilstein J. Org. Chem. 2020, 16, 858–870, doi:10.3762/bjoc.16.77

• phenols, ketones and 1,3-dienes (Scheme 6) [27]. C–C bond formation Complexes of radical and redox-active ligands with transition metals are known to be able to promote radical reactions through single-electron transfer (SET) processes [28]. Expanding on the research area pioneered by Wieghardt and

Combining enyne metathesis with long-established organic transformations: a powerful strategy for the sustainable synthesis of bioactive molecules

• Valerian Dragutan,
• Ileana Dragutan,
• Albert Demonceau and
• Lionel Delaude

Beilstein J. Org. Chem. 2020, 16, 738–755, doi:10.3762/bjoc.16.68

• the corresponding bicyclic dienic scaffolds. The subsequent hydroboration and aminohydroxylation carried out on these bicyclic dienes provided the AB subunit as a key intermediate component of manzamines A (16a) and E (16b, Scheme 19). Eventually, several highly elaborated transformations of the AB

Recent advances in Cu-catalyzed C(sp³)–Si and C(sp³)–B bond formation

• Balaram S. Takale,
• Ruchita R. Thakore,
• Elham Etemadi-Davan and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2020, 16, 691–737, doi:10.3762/bjoc.16.67

• tertiary carbon centers-bearing silicon products, although educts with initial tri-substitution led to lower isolated yields (e.g., 258). An unusual type of reaction has been described in which an acyl silane reacts with 1,3-dienes, under Cu catalysis, leading to an interesting class of α-silyl tertiary

• addition (e.g., 351, 352). It was shown that the presence of a heteroatom plays a crucial role due to the otherwise non-selective, facile addition of Cu-Bpin to alkenes (Scheme 56) [103]. Based on previous studies on asymmetric 3-component carboboration of styrene derivatives [104] and 1,3-dienes [105

• conversion of 2-substituted 1,3-dienes 376 into borocyano products using commercially available phosphine ligands (Scheme 60). Simply switching from a mono to a bidentate ligand resulted in 1,4 to 4,1-borocupration. The formation of allyl–Cu intermediates in the catalytic cycle readily trap available

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• species could be also involved mechanistically in the Ag-mediated reaction of enynals with conjugated dienes [18] and the homodimerization of enynals [19][20]. So, the studies on the reactions of alkynes involving the generation of silver carbene species from non-diazo precursors are of great value for

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• exocyclic C6 position have also been reported. For higher-order hepta- and nonafulvenes, the extended conjugated system also allows them to act as 8π components, as well as 2–6π components. Pentafulvenes can react as 2π components with moderately electron-deficient dienes and 4π components in reactions with

• fulvene to function as a 6π component in reactions with electron-deficient dienes (Scheme 5b) and fulvenes acting as dipolarophiles have been reported for enantioselective [6 + 3] and [3 + 2] cycloadditions [83][84][105]. In general, reactions with electron-rich alkenes will take place preferentially at

• reacting partner in the structure [91][119][127]. For example, pentafulvenes tethered to various dienes have been employed as precursors to various polycyclic ring systems, including kigelinol, neoamphilectane and kempane skeletons, which can be formed in a stereospecific manner depending upon the tether

Catalytic asymmetric oxo-Diels–Alder reactions with chiral atropisomeric biphenyl diols

• Chi-Tung Yeung,
• Wesley Ting Kwok Chan,
• Wai-Sum Lo,
• Ga-Lai Law and
• Wing-Tak Wong

Beilstein J. Org. Chem. 2019, 15, 955–962, doi:10.3762/bjoc.15.92

• reactions. Oxo-Diels–Alder (oxo-DA) reactions between electron-poor aldehydes and electron-rich dienes such as Danishefsky’s dienes or Brassard’s dienes are efficient ways to construct oxygen-containing six-membered heterocycles via [4 + 2] cyclizations, and have been dominated by metal-based chiral Lewis

Hoveyda–Grubbs catalysts with an N→Ru coordinate bond in a six-membered ring. Synthesis of stable, industrially scalable, highly efficient ruthenium metathesis catalysts and 2-vinylbenzylamine ligands as their precursors

• Kirill B. Polyanskii,
• Kseniia A. Alekseeva,
• Pavel V. Raspertov,
• Pavel A. Kumandin,
• Eugeniya V. Nikitina,
• Atash V. Gurbanov and
• Fedor I. Zubkov

Beilstein J. Org. Chem. 2019, 15, 769–779, doi:10.3762/bjoc.15.73

• way in lower yields [32]. The third part of this study was devoted to the demonstration of catalytic properties of metallo-complexes 11 in “standard” metathesis reactions (Scheme 6, Table 3). As a model substrate we chose easily available alkenes and dienes, such as i) styrene (12) and allylbenzene

• small amount of the starting compound 14 underwent polymerisation. The utility of the catalyst for the RCM reaction was demonstrated by the cyclization of dienes 17 and 19 (Table 3, entries 25–33) in both air and argon atmosphere. The complexes 11a, 11b and 11d in the air atmosphere provided cyclic

• alkenes 18, 20 with a strong admixture of initial dienes (Table 3, entries 25, 26, 29). Under argon atmosphere, the same transformations provided good results in the presence of 0.1–0.01 mol % of catalysts 11b,d (Table 3, entries 28, 30–32). Similarly, in the case of the ROCM reactions (Scheme 6

Application of olefin metathesis in the synthesis of functionalized polyhedral oligomeric silsesquioxanes (POSS) and POSS-containing polymeric materials

• Patrycja Żak and
• Cezary Pietraszuk

Beilstein J. Org. Chem. 2019, 15, 310–332, doi:10.3762/bjoc.15.28

• silsesquioxanes (POSS) and POSS-containing polymeric materials. Three types of processes, i.e., cross metathesis (CM) of vinyl-substituted POSS with terminal olefins, acyclic diene metathesis (ADMET) copolymerization of divinyl-substituted POSS with α,ω-dienes and ring-opening metathesis polymerization (ROMP) of

• metathesis in chemistry of unsaturated derivatives of POSS is limited to three types of processes, i.e., cross metathesis (CM) of vinyl-substituted POSS with terminal olefins, acyclic diene metathesis (ADMET) copolymerization of divinyl-substituted POSS with α,ω-dienes and ring-opening metathesis

• the application of ADMET in the synthesis of oligomers or polymers containing a POSS unit in the main chain. Marciniec disclosed ADMET copolymerization of DDSQ-2SiVi with dienes in the stereoselective synthesis of a new class of vinylene–arylene copolymers containing double-decker silsesquioxanes in

Synthesis of 1,2-divinylcyclopropanes by metal-catalyzed cyclopropanation of 1,3-dienes with cyclopropenes as vinyl carbene precursors

• Jesús González,
• Alba de la Fuente,
• María J. González,
• Laura Díez de Tejada,
• Luis A. López and
• Rubén Vicente

Beilstein J. Org. Chem. 2019, 15, 285–290, doi:10.3762/bjoc.15.25

• Abstract The synthesis of 1,2-divinylcyclopropanes by the reaction of cyclopropenes with 1,3-dienes is reported. The process relies on the ability of ZnCl2 or [Rh2(OAc)4] to generate metal–vinyl carbene intermediates from cyclopropenes, which effect cyclopropanation of 1,3-dienes. Most of the reactions

• proceeded in reasonable yields while the diastereoselectivity strongly depends on the structure of the diene. An example of an intramolecular process as well as the use of furan and 1,4-cyclohexadiene as dienes are also reported. Keywords: cyclopropanation; cyclopropenes; dienes; divinylcyclopropanes

• cyclopropanecarboxaldehydes [10] or reactions of metallated vinylcyclopropanes with suitable electrophiles are commonly employed (Scheme 1a) [11][12][13]. In a more convergent approach where the cyclopropane ring is created at the last stage, divinylcyclopropanes can be prepared by cyclopropanation of 1,3-dienes with metal

Oxidative radical ring-opening/cyclization of cyclopropane derivatives

• Yu Liu,
• Qiao-Lin Wang,
• Zan Chen,
• Cong-Shan Zhou,
• Bi-Quan Xiong,
• Pan-Liang Zhang,
• Chang-An Yang and
• Quan Zhou

Beilstein J. Org. Chem. 2019, 15, 256–278, doi:10.3762/bjoc.15.23

• alkylidenecyclopropanes 1 with allylic bromides 78 for the synthesis of 2-bromo-1,6-dienes 79 via radical ring-opening and SH2’ reactions (path V in Scheme 17) [95]. The experimental results suggested that radical carbonylation could also be incorporated in the reaction sequence, leading to 2-bromo-1,7-dien-5-ones 80

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• tested for the ethenolysis of cyclic olefins to selectively form α,ω-dienes, along with other 23 Ru benzylidene complexes featuring NHC ligands that differ in steric and electronic properties [50]. It is worth to underline that this transformation mediated by ruthenium initiators is less well

• investigated, presumably as a consequence of the high activity of ruthenium catalysts toward the competitive ROMP that is leading to low yields of terminal dienes. Among all the investigated systems, N-CF3 complex 153 emerged as the best performing catalyst in the ethenolysis of cis-cyclooctene (47), giving 96

• functionalized α,ω-dienes was thus accomplished in useful yields (>70%). In order to explain the selectivity observed in the ethenolysis of cyclic olefins, steric and electronic descriptors of the NHC ligands obtained computationally were evaluated. The main role in controlling selectivity was ascribed to the π

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• (Table 2, entry 11), implicating that the redox process is partially operating along with the main radical chain process. Norbornene (2m) was found reactive for degenerative transfer of xanthate 1a (Table 2, entry 12). The reaction was also applied to dienes 2n and 2o, which led the formation of

Generation of 1,2-oxathiolium ions from (arysulfonyl)- and (arylsulfinyl)allenes in Brønsted acids. NMR and DFT study of these cations and their reactions

• Stanislav V. Lozovskiy,
• Alexander Yu. Ivanov,
• Olesya V. Khoroshilova and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2018, 14, 2897–2906, doi:10.3762/bjoc.14.268

• reaction products: conjugated dienes, allyl alcohols, or thiochromene 1,1-dioxides. These reactions open new opportunities for organic synthesis based on electrophilic activation of sulfur containing allenes. X-ray crystal structures of compounds 2h (CCDC 1843276), 3e (CCDC 1843277), 5c (CCDC 1580895), 7b

Domino ring-opening–ring-closing enyne metathesis vs enyne metathesis of norbornene derivatives with alkynyl side chains. Construction of condensed polycarbocycles

• Ritabrata Datta and
• Subrata Ghosh

Beilstein J. Org. Chem. 2018, 14, 2708–2714, doi:10.3762/bjoc.14.248

• system. Domino metathesis of oxa- and aza-norbornenes with alkyne side chains [38][39][40] as well as norbornene derivatives having ether linked alkynes [41][42] in combination with Diels–Alder reaction of the resulting 1,3-dienes have been investigated to construct polycycles with heteroatoms. In spite

Ring-opening metathesis of some strained bicyclic systems; stereocontrolled access to diolefinated saturated heterocycles with multiple stereogenic centers

• Zsanett Benke,
• Melinda Nonn,
• Márton Kardos,
• Santos Fustero and
• Loránd Kiss

Beilstein J. Org. Chem. 2018, 14, 2698–2707, doi:10.3762/bjoc.14.247

• transformations, cyclic dienes with different ring sizes might be considered to be important starting materials for the generation of structurally diverse molecules. Among the large number of possible transformations, the ring olefinic bond of alicyclic dienes may lead to valuable β-lactams [21][22][23] or γ

• Recently, we have demonstrated the high utility of various constrained cyclic dienes, such as norbornadiene as well as 1,5- and 1,3-cyclooctadienes in the context of their applicability towards the access of diverse, highly functionalized olefinated molecules [14][15][16]. The corresponding β-lactams

Synergistic approach to polycycles through Suzuki–Miyaura cross coupling and metathesis as key steps

• Sambasivarao Kotha,
• Milind Meshram and
• Chandravathi Chakkapalli

Beilstein J. Org. Chem. 2018, 14, 2468–2481, doi:10.3762/bjoc.14.223

• with G-I catalyst 1 under ethylene, which resulted in the formation of the dienes 97a (63%) and 97b (83%, Scheme 15). Further, treatment of dienes 97a,b with dimethyl acetylenedicarboxylate (DMAD, 98) separately delivered the corresponding cycloadducts. Subsequently, aromatization was achieved by using

Cobalt- and rhodium-catalyzed carboxylation using carbon dioxide as the C1 source

• Tetsuaki Fujihara and
• Yasushi Tsuji

Beilstein J. Org. Chem. 2018, 14, 2435–2460, doi:10.3762/bjoc.14.221

• acid derivatives. Diene 14a was converted into the corresponding carboxylic acid 15a in good yield. In addition, 1,4-dienes having cyclohexenyl and geminal diphenyl substituents (14b and 14c) produced their corresponding linear carboxylic acids 15b and 15c in 78% and 57% yields, respectively. Substrate

• using alkynes [63][64][65][66], alkenes [67][68], allenes [69][70][71] and 1,3-dienes [72][73] have been reported. In this regard, Mikami et al. reported the Rh-catalyzed hydrocarboxylation of styrene derivatives depicted in Scheme 33 [74]. The desired reaction proceeded using [RhCl(cod)]2 as a catalyst

Cobalt-catalyzed nucleophilic addition of the allylic C(sp³)–H bond of simple alkenes to ketones

• Tsuyoshi Mita,
• Masashi Uchiyama,
• Kenichi Michigami and
• Yoshihiro Sato

Beilstein J. Org. Chem. 2018, 14, 2012–2017, doi:10.3762/bjoc.14.176

• to the case of nucleophilic η1-allylpalladium species [31][32][33][34][35][36][37][38][39]), whereas the cobalt atom preferred to reside at the internal position when allylarenes and 1,4-dienes were employed in our previous studies [28][29]. Subsequently, reductive elimination of methane from III