Borylation and rearrangement of alkynyloxiranes: a stereospecific route to substituted α-enynes

• Ruben Pomar Fuentespina,
• José Angel Garcia de la Cruz,
• Gabriel Durin,
• Victor Mamane,
• Jean-Marc Weibel and
• Patrick Pale

Beilstein J. Org. Chem. 2019, 15, 1416–1424, doi:10.3762/bjoc.15.141

• rearrangement of the so-formed alkynyloxiranyl borates. This stereospecific process overall transfers the cis or trans-stereochemistry of the starting alkynyloxiranes to the resulting 1,3-enynes. Keywords: boron; enyne; lithium; oxirane; rearrangement; Introduction Lithiated oxiranes are useful intermediates

• (see below) to be trapped by various phenylboronic esters 2. The resulting borate intermediate afforded the tetrasubstituted enyne 3 in good to moderate yields, depending on the boronic ester’s nature (Table 1). The catechol ester 2a only provided a modest yield of 3 (Table 1, entry 1), while the

• isomers. The cis-configured compound cis-1b readily reacted with pinacol phenylboronate 2c under the conditions set up above, providing enyne 4 as the sole product in high yield (Table 2, entry 1). NMR analysis revealed the Z-stereochemistry of this enyne [31]. In contrast, the trans-isomer trans-1b

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

• investigated with the objective of constructing condensed polycyclic structures. This investigation demonstrated that the generally observed domino reaction course involving a ring-opening metathesis of the norbornene unit and a ring-closing enyne metathesis is influenced to a great extent by the nature of the

• functional group and the substrate structure and may follow a different reaction course than what is usually observed. In cases where ROM–RCEYM occurred, the resulting 1,3-diene reacts in situ with the dienophile to provide condensed tetracyclic systems. Keywords: Diels–Alder reaction; domino process; enyne

• ][28][29][30][31][32][33] for the synthesis of a variety of complex ring systems such as condensed, bridged and spirocycles difficult to obtain otherwise. On the contrary, the domino process involving a ring-opening metathesis (ROM) followed by a ring-closing enyne metathesis (RCEYM) [34][35][36][37

Synthesis of cis-hydrindan-2,4-diones bearing an all-carbon quaternary center by a Danheiser annulation

• Gisela V. Saborit,
• Carlos Cativiela,
• Ana I. Jiménez,
• Josep Bonjoch and
• Ben Bradshaw

Beilstein J. Org. Chem. 2018, 14, 2597–2601, doi:10.3762/bjoc.14.237

• through ring-expanding cyclopentane annulations based on a Prins–pinacol rearrangement [17][18] and Au(I)-catalyzed pinacol-terminated 1,6-enyne cyclizations [19][20], the C3a–C7a bond formation occurring in the last step of both procedures. Finally, Snyder gained access to the type A hydrindane nucleus

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

• Diels–Alder reaction, Claisen rearrangement, cross-metathesis, and cross-enyne metathesis are used. The synergistic combination of these powerful reactions is found to be useful for the construction of complex targets and fulfill synthetic brevity. Keywords: Claisen rearrangement; Diels–Alder reaction

• a CM in an efficient manner. Biaryl derivatives In view of the interesting properties of biaryl derivatives, we have identified a three-step sequence, which involve cross-enyne metathesis (CEM), DA reaction followed by SM coupling [46]. To this end, acetylene derivatives 96a,b were subjected to CEM

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

• mild electron-rich ligand resulted in hydroacylation product (Scheme 33b) [94]. A plausible mechanism for the hydroarylative cyclization of enynes was shown in Scheme 34. The reaction begins with the reduction of Co(II) to Co(I) by Zn dust. The enyne compound underwent oxidative addition with Co(I) to

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

• species (Figure 1). However, the substrates employed have been restricted to allylarenes and 1,4-enyne, and 1,4-diene derivatives and α-olefins were totally unexplored. Therefore, the next challenge would be to use less reactive α-olefins (pKa value of 1-propene = 43). In this paper, we describe an

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• the alkene moiety of the 1,7-enyne, two consecutive cyclizations lead to the final sulfonylated benzo[α]fluoren-5-one. Electron and proton transfer and subsequent formation of dihydrogen close the catalytic cycle and regenerate the photocatalyst. Sulfinamides Formation of sulfoxides A new method for

Synthesis of substituted Z-styrenes by Hiyama-type coupling of oxasilacycloalkenes: application to the synthesis of a 1-benzoxocane

• James R. Vyvyan,
• Courtney A. Engles,
• Scott L. Bray,
• Erik D. Wold,
• Christopher L. Porter and
• Mikhail O. Konev

Beilstein J. Org. Chem. 2017, 13, 2122–2127, doi:10.3762/bjoc.13.209

• ][17][18][19][20][21] and enyne metathesis [22][23]. We became interested in the cross-coupling of cyclic siloxanes in the context of preparing trisubstituted Z-styrenes for the synthesis of natural product targets [24]. Heliannuol A was the first member of a family of allelopathic [25][26][27

The chemistry and biology of mycolactones

• Matthias Gehringer and
• Karl-Heinz Altmann

Beilstein J. Org. Chem. 2017, 13, 1596–1660, doi:10.3762/bjoc.13.159

Unpredictable cycloisomerization of 1,11-dien-6-ynes by a common cobalt catalyst

• Abdusalom A. Suleymanov,
• Dmitry V. Vasilyev,
• Valentin V. Novikov,
• Yulia V. Nelyubina and
• Dmitry S. Perekalin

Beilstein J. Org. Chem. 2017, 13, 639–643, doi:10.3762/bjoc.13.62

• the diene compounds 3a,b in 90–95% yields. These compounds were also obtained using a 1,2-bis(diphenylphosphino)benzene (dppbz) ligand. Despite the extensive studies of enyne transformations, this type of cyclization has been achieved only recently, using a cyclobutadiene rhodium complex as a catalyst

Chiral cyclopentadienylruthenium sulfoxide catalysts for asymmetric redox bicycloisomerization

• Barry M. Trost,
• Michael C. Ryan and
• Meera Rao

Beilstein J. Org. Chem. 2016, 12, 1136–1152, doi:10.3762/bjoc.12.110

• alcohols revealed a matched/mismatched effect that was strongly dependent on the nature of the solvent. Keywords: asymmetric catalysis; [3.1.0] bicycles; [4.1.0] bicycles; cycloisomerization; 1,6-enyne; 1,7-enyne; ruthenium catalysis; sulfoxide; Introduction Due to their prevalence in natural products [1

• ], medicinal targets [2], and materials [3], organic chemists have made the construction of cyclic, organic molecules one of the most important areas of research in their discipline. Of the available methods to affect cyclization, transition metal-catalyzed enyne cycloisomerizations [4] have been recognized as

• an atom- [5], step- [6], and redox-economical [7] class of reactions that are able to stitch together cyclic molecules quickly and efficiently. The very first enyne cycloisomerization reactions were reported by the Trost group while they were synthesizing substrates intended for thermal Alder–ene

Solving the puzzling competition of the thermal C²–C⁶ vs Myers–Saito cyclization of enyne-carbodiimides

• Anup Rana,
• Mehmet Emin Cinar,
• Debabrata Samanta and
• Michael Schmittel

Beilstein J. Org. Chem. 2016, 12, 43–49, doi:10.3762/bjoc.12.6

• Anup Rana Mehmet Emin Cinar Debabrata Samanta Michael Schmittel Department of Chemistry and Biology, Universität Siegen, Adolf-Reichwein-Str. 2, D-57068 Siegen, Germany 10.3762/bjoc.12.6 Abstract The mechanism of the thermal cyclization of enyne-carbodiimides 7a–c has been studied computationally

• by applying the DFT method. The results indicate that enyne-carbodiimides preferentially follow the C2–C6 (Schmittel) cyclization pathway in a concerted fashion although the Myers–Saito diradical formation is kinetically preferred. The experimentally verified preference of the C2–C6 over the Myers

• –Saito pathway is guided by the inability of the Myers–Saito diradical to kinetically compete in the rate-determining trapping reactions, either inter- or intramolecular, with the concerted C2–C6 cyclization. As demonstrated with enyne-carbodiimide 11, the Myers–Saito channel can be made the preferred

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• aldehyde groups were acceptable as para or meta-substituents on the aromatic ring at the β-positions (Table 2, entries 6–9). The alkynoate 3f bearing a 2-thienyl group at the β-position is also compatible with the conjugate addition and gave 94% syn selectivity (Table 2, entry 10). The 1,3-enyne derivative

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• temperature (Scheme 11) [48]. This method was used to prepare polycyclic scaffolds that can be encountered in diverse alkaloid natural products such as coralyne and berberine (Scheme 12) [49]. Similarly, enyne ring-closing metathesis reactions were performed to access a variety of vinyl-3,4

• . Enyne ring-closing metathesis. Synthesis of (R)-(+)-muscopyridine using a RCM strategy. Synthesis of a tris-pyrrole macrocycle. Synthesis of a bicyclic imidazole. RCM using Schrock’s catalyst 44. Synthesis of 1,6-pyrido-diazocine 46 by using a RCM. Synthesis of fused pyrimido-azepines through RCM. RCM

Ru complexes of Hoveyda–Grubbs type immobilized on lamellar zeolites: activity in olefin metathesis reactions

• Hynek Balcar,
• Naděžda Žilková,
• Martin Kubů,
• Michal Mazur,
• Zdeněk Bastl and
• Jiří Čejka

Beilstein J. Org. Chem. 2015, 11, 2087–2096, doi:10.3762/bjoc.11.225

• of 1,7-octadiene and (−)-β-citronellene; HGIIN+Cl− on SBA-15 (HGIIN+Cl−/SBA-15) was the most active (TON up to 16000 in RCM of citronellene). HGIIN+Cl−/SBA-15 proved its versatility in RCM, enyne metathesis, metathesis of methyl oleate, and cross-metathesis of electron deficient methyl acrylate with

Recent applications of ring-rearrangement metathesis in organic synthesis

• Sambasivarao Kotha,
• Milind Meshram,
• Priti Khedkar,
• Shaibal Banerjee and
• Deepak Deodhar

Beilstein J. Org. Chem. 2015, 11, 1833–1864, doi:10.3762/bjoc.11.199

• decades have changed the landscape of organic synthesis. Armed with these advances, olefin metathesis has become a staple in retrosynthesis. Metathesis protocols such as ring-closing metathesis (RCM), cross-metathesis (CM), and enyne metathesis (EM) have gained popularity in the synthesis of complex

• related to the RRM readers may refer to excellent reviews available in the literature [3][4][5][6]. Review Cyclopropene systems Cyclopropene derivatives are highly strained systems and they are ideal candidates for the RRM process. In this context, Zhu and Shi [7] have reported the ring-closing enyne

• catalyst 2 to generate the expected RRM product 97 in 68% yield. Further, this approach is useful for the preparation of polyunsaturated trisaccharides (Scheme 19). Mori and co-workers [24] have used the RRM protocol starting with enyne 98 using catalyst 2 in the presence of ethylene (24) to generate the

Preparation of conjugated dienoates with Bestmann ylide: Towards the synthesis of zampanolide and dactylolide using a facile linchpin approach

• Jingjing Wang,
• Samuel Z. Y. Ting and
• Joanne E. Harvey

Beilstein J. Org. Chem. 2015, 11, 1815–1822, doi:10.3762/bjoc.11.197

• the C3–C8 fragment of zampanolide, was synthesised from acrolein (12) (Scheme 2). Firstly, Barbier reaction of acrolein with propargyl bromide followed by silyl protection of the resulting alcohol afforded enyne 13. Treatment of the lithium alkynylide derived from 13 with methyl chloroformate produced

Latent ruthenium–indenylidene catalysts bearing a N-heterocyclic carbene and a bidentate picolinate ligand

• Thibault E. Schmid,
• Florian Modicom,
• Adrien Dumas,
• Etienne Borré,
• Loic Toupet,
• Olivier Baslé and
• Marc Mauduit

Beilstein J. Org. Chem. 2015, 11, 1541–1546, doi:10.3762/bjoc.11.169

• -diisopropylphenyl)imidazolidin-2-ylidene) demonstrated excellent latent behaviour in ring closing metathesis (RCM) reaction and could be activated in the presence of a Brønsted acid. The versatility of the catalyst 4a was subsequently demonstrated in RCM, cross-metathesis (CM) and enyne metathesis reactions

• by HCl addition. The versatility of the catalyst was subsequently demonstrated in RCM, CM and enyne metathesis reactions. Solid-state structure of complex 4a from single crystal X-ray diffraction. Hydrogens have been omitted for clarity. (N in blue, C in grey, O in red, Cl in green). Olefin

• . Synthesis of complex 4a and 4b from (SIPr)(pyridine)RuCl2(indenylidene) (5). Substrate scope in RCM, CM and enyne metathesis catalyzed by 4aa. Supporting Information Supporting Information File 38: Full experimental procedures and detailed analytical data for ruthenium complexes. Acknowledgements This

Ruthenium indenylidene “1^st generation” olefin metathesis catalysts containing triisopropyl phosphite

• Stefano Guidone,
• Fady Nahra,
• Alexandra M. Z. Slawin and
• Catherine S. J. Cazin

Beilstein J. Org. Chem. 2015, 11, 1520–1527, doi:10.3762/bjoc.11.166

• higher catalytic activity was observed for Ind-I with 77% conversion when using 2 mol % pre-catalyst at 30 °C (Table 2, entry 13). Complex 1 was active in the ring-closing enyne metathesis (RCEYM) with 78% conversion of substrate 12 obtained with 1 mol % catalyst loading (Table 2, entry 14). A higher

Tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds

• Javier Miró,
• María Sánchez-Roselló,
• Álvaro Sanz,
• Fernando Rabasa,
• Carlos del Pozo and
• Santos Fustero

Beilstein J. Org. Chem. 2015, 11, 1486–1493, doi:10.3762/bjoc.11.161

• Abstract A new tandem cross enyne metathesis (CEYM)–intramolecular Diels–Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of

• linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM–IMDAR protocols. Keywords: bicyclic frameworks; cross enyne metathesis; Diels–Alder

• reaction; tandem reaction; Introduction Among all metathetic processes, the enyne metathesis reaction has received significant attention as an attractive and frequently used synthetic tool in organic synthesis [1][2][3][4][5][6][7]. It is an atom economical process that combines alkene and alkyne moieties

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

• treated with dilithiated 2-methyl-1-butene-3-yne (104) to generate the corresponding bis-enyne 105. Treatment with Pd(PPh3)4 in dry toluene under high dilution conditions at 100 °C afforded the exomethylene paracyclophane 106. The paracyclophane 106 was converted to oxocyclophane 107 by ozonolysis

• [141] reported the synthesis of meta-cyclophane 145 at room temperature by ring-closing alkyne metathesis of 1,3-bis(3-pentynyloxymethyl)benzenes (Figure 9). This strategy has also been extended to ortho and para-derivatives. Cross-enyne metathesis: Recently, Kotha and Waghule [142] have synthesized

• diverse crownophanes by using a cross-enyne metathesis and Diels–Alder (DA) reaction as key steps. Here, the macrocycles 146 and 149 were subjected to a cross-enyne metathesis protocol with ethylene to generate the dienes 147 and 150, respectively. These dienes were subjected to a DA reaction with

Synthesis and chemosensing properties of cinnoline-containing poly(arylene ethynylene)s

• Natalia A. Danilkina,
• Petr S. Vlasov,
• Semen M. Vodianik,
• Andrey A. Kruchinin,
• Yuri G. Vlasov and
• Irina A. Balova

Beilstein J. Org. Chem. 2015, 11, 373–384, doi:10.3762/bjoc.11.43

• depicted in Figure 9 and Figure 11 were observed. Previously palladium(II)-alkyne π-complexes have been proposed as intermediates in Pd(II)-catalyzed diamination of alkynes [63], enyne coupling [64], hydroarylation of alkynes [65], inramolecular carbocyclization [66] and other reactions. Some types of

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• phenanthridine core starting from a simple disubstituted aniline relied on the aza-Claisen rearrangement, ring-closing enyne metathesis and Diels–Alder reaction [41] (Scheme 18). The obtained phenanthridine derivatives were polysubstituted at the phenyl side-rings, while retaining the unsubstituted central

Organic chemistry on surfaces: Direct cyclopropanation by dihalocarbene addition to vinyl terminated self-assembled monolayers (SAMs)

• Malgorzata Adamkiewicz,
• David O’Hagan and
• Georg Hähner

Beilstein J. Org. Chem. 2014, 10, 2897–2902, doi:10.3762/bjoc.10.307

• of vinyl-terminated SAMs has been demonstrated, e.g., through surface modification of radicals generated by C–O bond thermolysis [17] and in a more controlled sense via olefin cross metathesis/enyne metathesis [18] of mixed vinyl and acetylenyl-terminated SAMs followed by Diels–Alder modifications of

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• particular, the electrophilic enyne intermediate [32][40], which is trespassed in the three-component synthesis of solid-state luminescent push–pull indolones 4, intrigued our interest for accessing even triene push–pull systems and to study their electronic properties. Here we report our findings on the