Total synthesis of grayanane natural products

• Nicolas Fay,
• Rémi Blieck,
• Cyrille Kouklovsky and
• Aurélien de la Torre

Beilstein J. Org. Chem. 2022, 18, 1707–1719, doi:10.3762/bjoc.18.181

• cyclization based on a bridgehead tertiary carbocation intermediate forging the B ring; iii) redox manipulations and a 1,2-migration as final steps. The synthesis started from (S)-ketone 44 which was prepared via asymmetric CBS reduction of diketone 26 (Scheme 7). Firstly, this (S)-ketone 44 was transformed

Acid-catalyzed rearrangements in arenes: interconversions in the quaterphenyl series

• Sarah L. Skraba-Joiner,
• Carter J. Holt and
• Richard P. Johnson

Beilstein J. Org. Chem. 2019, 15, 2655–2663, doi:10.3762/bjoc.15.258

• present work, we have explored rearrangements of quaterphenyls, the next homolog in the paraphenylene series, now with six structural isomers. Scheme 2 summarizes interconnections via 1,2-migration of a terminal phenyl group. As will be shown below, an internal aryl–aryl bond can also be transposed

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• also described, with a focus on radical-involved reactions in terms of organic synthesis. Keywords: dehalogenation; electrolysis; green chemistry; heptamethyl cobyrinate; methyl transfer; 1,2-migration; photosensitizer; vitamin B12; Review 1. Introduction 1-1. Redox and coordination chemistry of B12

• catalytic reactions We deeply investigated the electrochemical catalytic reactions mediated by 1 and related complexes and succeeded in the functional simulations of MMCM-type 1,2-migration reactions [42]. For example, when 2,2-bis(ethoxycarbonyl)-1-bromopropane was selected as a model substrate, the 1,2

• reaction conditions. Mechanistic investigations revealed that the formation of the two-electron-reduced species of Co(III)-monoalkylated complex of 1 was vital for carbon-skeleton rearrangement reactions. It was also discovered that the 1,2-migration of the carboxylic ester group proceeded via an anionic

Synthesis of new tricyclic 5,6-dihydro-4H-benzo[b][1,2,4]triazolo[1,5-d][1,4]diazepine derivatives by [3⁺ + 2]-cycloaddition/rearrangement reactions

• Lin-bo Luan,
• Zi-jie Song,
• Zhi-ming Li and
• Quan-rui Wang

Beilstein J. Org. Chem. 2018, 14, 1826–1833, doi:10.3762/bjoc.14.155

• followed by a ring-expansion rearrangement. In the rearrangement reaction, the phenyl substituent in the initially formed spiro-triazolium adducts 16 underwent a [1,2]-migration from C(3) to the electron-deficient N(2). This led to the ring expansion from 6-membered piperidine to 7-membered diazepine

Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

• Takeshi Fujita,
• Ryo Kinoshita,
• Tsuyoshi Takanohashi,
• Naoto Suzuki and
• Junji Ichikawa

Beilstein J. Org. Chem. 2017, 13, 2682–2689, doi:10.3762/bjoc.13.266

• elimination from 2a, 1,2-migration of the phenyl group, and deprotonation, followed by hydrolysis of the resulting doubly activated benzylic difluoromethylene unit (Scheme 2). Neither a combination of bis(pyridine)iodonium (IPy2BF4) and trifluoromethanesulfonic acid nor a combination of I2 and silver(I

Unusual reactions of diazocarbonyl compounds with α,β-unsaturated δ-amino esters: Rh(II)-catalyzed Wolff rearrangement and oxidative cleavage of N–H-insertion products

• Valerij A. Nikolaev,
• Jury J. Medvedev,
• Olesia S. Galkina,
• Ksenia V. Azarova and
• Christoph Schneider

Beilstein J. Org. Chem. 2016, 12, 1904–1910, doi:10.3762/bjoc.12.180

• nucleophilic 1,2-migration of aryl (Ph) or alkyl (Me) group R2 occurs, producing α-oxoketene D. The latter interacts with N–H-group of the aminoester 1 to give acylamides 6a–c. Predominance of the Wolff rearrangement over typical carbenoid reactions (N–H-insertion, etc.) in the case of diazodicarbonyl

Rearrangements of organic peroxides and related processes

• Ivan A. Yaremenko,
• Vera A. Vil’,
• Dmitry V. Demchuk and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162

On the mechanism of imine elimination from Fischer tungsten carbene complexes

• Philipp Veit,
• Christoph Förster and
• Katja Heinze

Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125

• accordance with the established mechanism of 1,2-migration reactions of carbenes [47][48][68][69][70][71]. Interestingly, the 1,2-H-shift of Z-2 (Z-2 → Z-3: ΔG‡ = 179 kJ mol−1) with a lower barrier occurs within the C–C(carbene)–N plane via a direct interaction of the nσ orbital at the carbene carbon atom

Recent applications of the divinylcyclopropane–cycloheptadiene rearrangement in organic synthesis

• Sebastian Krüger and
• Tanja Gaich

Beilstein J. Org. Chem. 2014, 10, 163–193, doi:10.3762/bjoc.10.14

• formation gives rise to either cis- or trans-divinylcyclopropanes 268/271. cis-Divinylcyclopropane 271 can readily undergo DVCPR to give bicycle 272. 1,2-Migration of the migrating group G leads to final bicycle 273 after regeneration of the catalyst. Trans-divinylcyclopropane 268 can undergo DVCPR after

• 1,2-migration and subsequent formation of cis-divinylcyclopropane 269 yielding bridged bicycle 270. Chung and coworkers [210] discovered a related reaction pattern using platinum(II) as the catalyst. Depending on the attached rests on enyne 276 both possible cycloheptadienes (bridged 277 or annulated

Gold(I)-catalyzed enantioselective cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2013, 9, 2250–2264, doi:10.3762/bjoc.9.264

• a nucleophilic intramolecular attack of the carboxy moiety on the activated alkyne. 1,2-Migration of the ester affording a gold–carbene of type A is usually preferred when a terminal alkyne is used [38][39][40]. Based on this concept, several groups have shown that the resulting carbenoid

Gold(I)-catalyzed formation of furans from γ-acyloxyalkynyl ketones

• Marie Hoffmann,
• Solène Miaskiewicz,
• Jean-Marc Weibel,
• Patrick Pale and
• Aurélien Blanc

Beilstein J. Org. Chem. 2013, 9, 1774–1780, doi:10.3762/bjoc.9.206

• -acyloxyalkynyl ketones were efficiently converted into highly substituted furans with 2.5 mol % of triflimide (triphenylphosphine)gold(I) as a catalyst in dichloroethane at 70 °C. Keywords: alkynyl ketones; cycloisomerization; furans; gold-catalysis; 1,2-migration; Introduction Furans are an important class of

• latter have already been described to rearrange into furans by using copper catalysts. Indeed, Gevorgyan et al. showed that the combination of copper(I) chloride and triethylamine catalyzed the 1,2-migration/cycloisomerization of γ-acyloxyalkynyl ketones in dimethylacetamide (DMA) at 130 °C (Scheme 2

• the crude residue was purified by silica gel flash chromatography (pentane/Et2O). Gold(I) or gold(III)-catalyzed furan syntheses with or without nucleophiles. Copper(I)-catalyzed 1,2-migration/cycloisomerization of γ-acyloxyalkynyl ketones. Mechanistic hypothesis for gold(I)-catalyzed conversion of γ

Palladium-catalyzed dual C–H or N–H functionalization of unfunctionalized indole derivatives with alkenes and arenes

• Gianluigi Broggini,
• Egle M. Beccalli,
• Andrea Fasana and
• Silvia Gazzola

Beilstein J. Org. Chem. 2012, 8, 1730–1746, doi:10.3762/bjoc.8.198

• /esterification process through iminium intermediates. Cyclization of 3-indolylallylcarboxamides involving 1,2-migration of the acyl group from spiro-intermediates. Domino reactions of 2-indolylallylcarboxamides involving N–H functionalization. Cyclization/acyloxylation reaction of 3-alkenylindoles. Doubly

Efficient oxidation of oleanolic acid derivatives using magnesium bis(monoperoxyphthalate) hexahydrate (MMPP): A convenient 2-step procedure towards 12-oxo-28-carboxylic acid derivatives

• Jorge A. R. Salvador,
• Vânia M. Moreira,
• Rui M. A. Pinto,
• Ana S. Leal and
• José A. Paixão

Beilstein J. Org. Chem. 2012, 8, 164–169, doi:10.3762/bjoc.8.17

• group, creating a tertiary carbocation at C-13. Then, a concerted stereoselective 1,2-migration of the 12β-H to the 13β-position with the rearrangement of the 12α-hydroxy group affords the final 12-oxo-28-carboxylic acid structure [18]. The molecular structure of compound 11, determined by single

Access to pyrrolo-pyridines by gold-catalyzed hydroarylation of pyrroles tethered to terminal alkynes

• Elena Borsini,
• Gianluigi Broggini,
• Andrea Fasana,
• Chiara Baldassarri,
• Angelo M. Manzo and
• Alcide D. Perboni

Beilstein J. Org. Chem. 2011, 7, 1468–1474, doi:10.3762/bjoc.7.170

• pyrrolo[2,3-c]pyridines (Scheme 1) [33]. The reaction provided also the isomeric pyrrolo[3,2-c]pyridines arising from 1,2-migration of the amide moiety. Having recently broadened our studies toward gold catalysis [34][35], we have been intrigued by the investigation of a gold-catalyzed intramolecular

• on the C–C triple bond to direct the cyclization following 6-exo-dig or 7-endo-dig processes. Once again, the trend in terms of direct and rearranged product formation was dependent on the solvent, the 1,2-migration products being favoured in less polar solvents. The 7-endo-dig cyclizations of amides

Recent developments in gold-catalyzed cycloaddition reactions

• Fernando López and
• José L. Mascareñas

Beilstein J. Org. Chem. 2011, 7, 1075–1094, doi:10.3762/bjoc.7.124

• carboxyl unit on the metal-activated alkyne complex XXI. When a terminal alkyne is used (Figure 1, R = H), the 1,2-migration of the acetate moiety is preferred, affording an alkenyl–gold carbenoid species of type XXIII. In contrast, internal alkynes typically experience a 1,3-acyloxy migration rendering

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

• initiated by 1,2-indole migrations [132], the starting material, indole 247, was converted to an intermediate with [AuNTf2(Ph3P)]. Intramolecular attack of the indole on the activated alkyne gives the vinyl–gold complex, which is transformed into the gold carbene complex through a 1,2-migration of the

• substituted naphthalenes 296 [151]. This cascade reaction involves a tandem sequence of 1,3- and 1,2-migration of two different migrating groups. Jin and Yamamoto prepared the fused tri- and tetracyclic enones 298 through an efficient gold(III)-catalyzed tandem reaction, heteroenyne metathesis, and Nazarov

• allenoates 364 and various terminal alkynes [172]. The González group developed an intermolecular reaction of internal alkynes and imines, in which the propargyl tosylates 367 react with N-tosylaldimines 368 to afford cyclopent-2-enimines 369 [173]. The final product was achieved through a 1,2-migration of

When gold can do what iodine cannot do: A critical comparison

• Sara Hummel and
• Stefan F. Kirsch

Beilstein J. Org. Chem. 2011, 7, 847–859, doi:10.3762/bjoc.7.97

• cyclic oxonium ion is produced in the first stage of the cascade via both gold- and iodonium-triggered cyclization. In both cases, the heterocyclization is followed by a 1,2-migration onto the oxonium ion, where the only difference is whether the final product bears a H or an I atom at the C4-position

• transformations There are several gold-catalyzed processes for which there are no corresponding iodine counterparts. In general, most of the processes specific for gold are assumed to proceed via gold carbene intermediates. For example, 1,5-enynes 49 can react in gold-catalyzed domino reactions that include a 1,2

• -migration as an additional step (Scheme 14). Gold-induced activation of the alkyne followed by cyclization produces a cyclopropyl gold carbene 50 as the key intermediate. Depending on the substitution pattern, two alternative reaction outcomes are possible: The formation of bicyclo[3.1.0]hexane derivatives

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

• Paul W. Davies,
• Nicolas Martin and
• Neil Spencer

Beilstein J. Org. Chem. 2011, 7, 839–846, doi:10.3762/bjoc.7.96

• the most common fundamental steps in these skeletal rearrangements involves C–C bond fission through 1,2-migration. This step is triggered by the generation of carbocationic character, which is generally stabilised in some form, either by an adjacent gold atom or through extended delocalisation. While

Solvent- and ligand-induced switch of selectivity in gold(I)-catalyzed tandem reactions of 3-propargylindoles

• Estela Álvarez,
• Delia Miguel,
• Patricia García-García,
• Manuel A. Fernández-Rodríguez,
• Félix Rodríguez and
• Roberto Sanz

Beilstein J. Org. Chem. 2011, 7, 786–793, doi:10.3762/bjoc.7.89

• nucleophilic nature of indoles [15], which are known to react with gold-activated alkynes or allenes [16][17], and by taking advantage of our reported methodology for the synthesis of 3-propargylindoles [18][19], we have shown that the indole nucleus is able to participate in gold-catalyzed 1,2-migration

Synthetic applications of gold-catalyzed ring expansions

• David Garayalde and
• Cristina Nevado

Beilstein J. Org. Chem. 2011, 7, 767–780, doi:10.3762/bjoc.7.87

• , intermediates characterize these competitive processes, i.e., 1,2-migration via metal "carbenoid" 81 formation and [3,3]-sigmatropic rearrangement via allenyl acetate 82 as an intermediate (Scheme 24) [5][56][57]. In 2008, Toste and co-workers reported a gold(I)-catalyzed cycloisomerization of cis-pivaloyloxy

When cyclopropenes meet gold catalysts

• Frédéric Miege,
• Christophe Meyer and
• Janine Cossy

Beilstein J. Org. Chem. 2011, 7, 717–734, doi:10.3762/bjoc.7.82

• allylic carbocation 41. Subsequent 1,2-migration of the acetoxy group proceeded via the formation of five-membered intermediates 42 or 42', which then collapsed to the geometric isomers of the corresponding 2-acetoxydiene. For steric reasons, the energy barrier was found to be significantly lower for the

Unusual behavior in the reactivity of 5-substituted-1H-tetrazoles in a resistively heated microreactor

• Bernhard Gutmann,
• Toma N. Glasnov,
• Tahseen Razzaq,
• Walter Goessler,
• Dominique M. Roberge and
• C. Oliver Kappe

Beilstein J. Org. Chem. 2011, 7, 503–517, doi:10.3762/bjoc.7.59

• from the resulting azido group and a subsequent 1,2-migration of the acylimido group from carbon to nitrogen to give the same nitrilimine intermediate was ruled out by Herbst via 15N labeling studies [44]. The degradative acylation of 5-substituted-1H-tetrazoles with acyl halides is in fact an elegant