Synthesis of 1-indanones with a broad range of biological activity

• Marika Turek,
• Dorota Szczęsna,
• Marek Koprowski and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2017, 13, 451–494, doi:10.3762/bjoc.13.48

• reactions leading to intermediates 197 and 198 [85]. The authors have also synthesized other fluorenone derivatives 200–204 by using this method (Scheme 56). 1.6 From diazo compounds Hashimoto et al. have proposed the synthesis of optically active 1,1’-spirobi[indan-3,3’-dione] derivative 208 (up to 80

• % enantiomeric excess) from bis(α-diazo-β-keto ester) 205 [86]. The key step of this synthesis was a double intramolecular C–H insertion process catalyzed by dirhodium(II) tetrakis[N-phthaloyl-(R or S)-tert-leucinate]. The resulting spiroindanone derivative 207 obtained from the intermediate 206, underwent

• , potentially more selective than known compounds [87]. Transformation of diazo compounds 209 into 1-indanone derivatives 210, catalyzed by rhodium acetate, has been one of the steps in the total synthesis of atipamezole analogues 211 (Scheme 58). The most common symptom of the menopause is hot flash, which is

Catalytic Wittig and aza-Wittig reactions

• Zhiqi Lao and
• Patrick H. Toy

Beilstein J. Org. Chem. 2016, 12, 2577–2587, doi:10.3762/bjoc.12.253

• catalytic diaza-Wittig reactions (Scheme 20) [38]. In these reactions 76 (from the reduction of 44) was the catalyst that transformed diazo group containing starting materials 77 into pyridazine derivatives 78. In these reactions 44 was actually added to the reaction mixtures as the pre-catalyst that was

The in situ generation and reactive quench of diazonium compounds in the synthesis of azo compounds in microreactors

• Faith M. Akwi and
• Paul Watts

Beilstein J. Org. Chem. 2016, 12, 1987–2004, doi:10.3762/bjoc.12.186

• transfer synthesis’ in micro-chips for a diazo-coupling reaction [23]. The authors did not however employ a phase transfer catalyst, but rather the principle to increase the reaction selectivity in the diazo coupling of 5-methylresorcinol (10) to p-nitrobenzene diazonium tetrafloroborate (11) in a biphasic

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

• products. These oxidation processes are mediated by Rh(II) catalysts possessing perfluorinated ligands. The formation of pyrrolidine structures, characteristic for catalytic reactions of diazoesters, was not observed in these processes at all. Keywords: diazo compounds; N–H-insertion; oxidation cleavage

• intermediates generated from diazo compounds (ammonium, oxonium, C=X-ylides and others) to react with a variety of electrophiles/nucleophiles yielding complex and challenging organic molecules from relatively straightforward initial compounds [9][10]. The research group by Hu and co-workers elaborated recently

• system of the amino ester to afford N-arylpyrrolidines B (Scheme 1). It was suggested that this strategy for the synthesis of pyrrolidines could be extended to diazo compounds of other types and structures, and, as with diazoesters, multi-substituted pyrrolidines are the principal reaction products in

On the cause of low thermal stability of ethyl halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

• briefly studied the thermal, non-catalytic cyclopropanation of styrenes and compared the results to the analogous Rh(II)-catalyzed reactions. Keywords: carbenes; catalysis; cyclopropanation; halo diazoacetates; half-lives; thermal stability; Introduction The chemistry of diazo compounds has fascinated

• organic chemists ever since Theodor Curtius synthesized ethyl diazoacetate (EDA, 1) for the first time in 1883 [1]. Even today, after more than a century of research, diazo compounds still play an important role in state-of-the-art organic chemistry in areas such as for example C–H functionalization [2

• ]. The synthesis and properties of diazo compounds have been a topic of much interest, particularly relevant are their thermal stability and sensitivity towards Brønsted and Lewis acids. The monograph by Regitz and Maas gives an excellent overview on their preparation and properties [3]. The thermal

Multicomponent reactions: A simple and efficient route to heterocyclic phosphonates

• Mohammad Haji

Beilstein J. Org. Chem. 2016, 12, 1269–1301, doi:10.3762/bjoc.12.121

• prepare phosponylpyrazoles 217 in the presence of KOH in MeOH in 73–95% yields (Scheme 44) [82]. Based on their explanation, the treatment of dimethyldiazomethylphosphonate 213 with a nucleophilic base generates diazo compound 215. The subsequent [3 + 2] cycloaddition reaction of 215 with Knoevenagel

• developed for the preparation of different 3-carbo-5-phosphonylpyrazoles 223 (Scheme 45) [83]. The corresponding phosphonylpyrazoles 223 were formed via a Claisen–Schmidt/1,3-dipolar cycloaddition/oxidation process under basic conditions in MeOH in 30–91% yields. The dual reactivity of diethyl (1-diazo-2

The synthesis of functionalized bridged polycycles via C–H bond insertion

• Jiun-Le Shih,
• Po-An Chen and
• Jeremy A. May

Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97

• major product, with the minor product coming from the predicted second-most preferred conformation 84. The May group also showed that the cascade reaction could be initiated from hydrazones. In the course of this work, it was discovered that NaOSiMe3 was a superior base for hydrazone to diazo conversion

• gold ketocarbenes 104 from alkynes (Scheme 22) [95]. Those carbenes are then capable of further transformations, including C–H bond insertion and the reaction with other alkynes. Notably, this approach avoids the use of unstable diazo compounds. The Zhang group also demonstrated that the gold carbenes

Enantioselective carbenoid insertion into C(sp³)–H bonds

• J. V. Santiago and
• A. H. L. Machado

Beilstein J. Org. Chem. 2016, 12, 882–902, doi:10.3762/bjoc.12.87

• activation; chiral catalysis; diazo compounds; total synthesis; Introduction One of the major challenges met in organic synthesis is the formation of carbon–carbon bonds, in particular in a stereoselective way. Nucleophilic substitution reactions, radical reactions, cross-coupling reactions and the Heck

• the carbenoid intermediate can change its reactivity and hence the selectivity of the carbenoid reaction. The most commonly used diazo compounds rely on the formation of a donor/acceptor carbenoid intermediate type. The EWG increases the electrophilicity and reactivity of the donor/acceptor carbenoid

• -cuparenone (8) through the construction of a five-membered ring prepared by an enantioselective carbenoid insertion into a C(sp3)–H bond (Scheme 3) [34]. To carry out the cyclization, the carbenoid was formed by the action of Rh2(OAc)4 on the diazo compound 6. That intermediate intramolecularly inserted into

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

• (I) complexes. In some cases, high regioselectivity and enantioselectivity have been achieved in the C–H bond insertion of small alkanes. This review highlights the most recent accomplishments in this field. Keywords: alkane; diazo compounds; C–H bond functionalization; C–H bond insertion; metal

• chiral porphyrins D4-por*, the enantioselective intermolecular carbene insertion into C(sp3)–H bonds was achieved with moderate to high selectivities (Scheme 7). Besides, the reaction of diazo compounds with benzylic, allylic and alkane C(sp3)–H bonds afforded the insertion products in up to 80% yield

Diradical reaction mechanisms in [3 + 2]-cycloadditions of hetaryl thioketones with alkyl- or trimethylsilyl-substituted diazomethanes

• Grzegorz Mlostoń,
• Paulina Pipiak and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2016, 12, 716–724, doi:10.3762/bjoc.12.71

• products of the [3 + 2]-cycloaddition of the diazo dipole onto the C=S bond. The latter decompose only at higher temperature (ca. −40 °C) to generate thiocarbonyl S-isopropanide. In the absence of the starting thioketone, the corresponding thiiranes and/or ethene derivatives, formed from them via

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• [93]. Structures of the poly(acrylate)-based polymers PAAAzo (trans), PAAAzo (cis), PAA3α-CD and PAA6α-CD, and the effects of the stereochemistry and photo-isomerism of the diazo substituents of PAA3β-CD and PAA6β-CD on their host–guest complexation by the α-CD substituents of PAA3α-CD and PAA6α-CD

Catalytic asymmetric formal synthesis of beraprost

• Yusuke Kobayashi,
• Ryuta Kuramoto and
• Yoshiji Takemoto

Beilstein J. Org. Chem. 2015, 11, 2654–2660, doi:10.3762/bjoc.11.285

• condensation followed by diazo-transfer reaction. The chiral dihydrobenzofuran scaffold (5 or 6) could be synthesized by asymmetric intramolecular oxa-Michael reaction (AIOM) of α,β-unsaturated amides 7 or 8. Such reactions are generally considered to be challenging due to low nucleophilicity of the oxygen

Synthesis of bi- and bis-1,2,3-triazoles by copper-catalyzed Huisgen cycloaddition: A family of valuable products by click chemistry

• Zhan-Jiang Zheng,
• Ding Wang,
• Zheng Xu and
• Li-Wen Xu

Beilstein J. Org. Chem. 2015, 11, 2557–2576, doi:10.3762/bjoc.11.276

• diazo transfer agent (imidazole-1-sulfonyl azide) was performed to convert the amine group into the corresponding azide group, which provided a polymeric substrate for the second CuAAC reaction to give the desired bistriazoles (Scheme 23). In 2009, Zhu and co-workers found that copper(II) acetate (Cu

Evidencing an inner-sphere mechanism for NHC-Au(I)-catalyzed carbene-transfer reactions from ethyl diazoacetate

• Manuel R. Fructos,
• Juan Urbano,
• M. Mar Díaz-Requejo and
• Pedro J. Pérez

Beilstein J. Org. Chem. 2015, 11, 2254–2260, doi:10.3762/bjoc.11.245

• of a gold(I) source and a diazo compound. It was not until 2005 that the first example of this transformation was reported by our group [15][16], when the complex IPrAuCl (1) (IPr = 1,3-bis(diisopropylphenyl)imidazole-2-ylidene), in the presence of NaBArF4 (BArF4− = tetrakis(3,5-bis(trifluoromethyl

• the well-known instability of some of the diazo reagents. The reactions shown in Scheme 2 and Scheme 3 have been explained through the appearance of a [LAu=CR1R2]+ intermediate, not detected nor isolated, that further reacts with a non-coordinated nucleophile (i.e., by means of an outer-sphere

• mechanism). Those intermediates are quite reactive, in contrast to similar but low reactive gold–carbene complexes recently and independently described by the groups of Fürstner [19] and Straub [20]. Scheme 4a shows a generally accepted mechanism for the metal-catalyzed carbene transfer from diazo compounds

Olefin metathesis in air

• Lorenzo Piola,
• Fady Nahra and
• Steven P. Nolan

Beilstein J. Org. Chem. 2015, 11, 2038–2056, doi:10.3762/bjoc.11.221

• reaction with styrene, avoiding the use of hazardous diazo compound 7 [82]. Towards the end of 2013, a report by Olszewski, Skowerski and co-workers showed how a variety of commercially available catalysts (Figure 12) could be employed in air with nondegassed ACS grade green solvents. Their results were in

Synthesis of quinoline-3-carboxylates by a Rh(II)-catalyzed cyclopropanation-ring expansion reaction of indoles with halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2015, 11, 1944–1949, doi:10.3762/bjoc.11.210

• transition metal-catalyzed C–H functionalization by diazo compounds [5][6][7][8]. The reactions of indoles with electrophilic metal-bound carbenes, or carbenoids, generated from diazo compounds, takes place under mild reaction conditions. The reaction has been studied for the three principle classes of

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

• precursor 333 was obtained from diazo ester 331 in five steps. Further, the RRM of 333 with catalyst 2 furnished the required pyran derivative 334 (71%). Next, the fused ether 334 was transformed into the desired intermediate 335 in eight steps, which is a key intermediate required for the synthesis of

Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF₅-substituted phenylboronic esters and iodobenzenes

• George Iakobson,
• Junyi Du,
• Alexandra M. Z. Slawin and
• Petr Beier

Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162

• for an efficient reaction. Alkali metal acetates are known to facilitate decomposition of aryldiazonium salts by the formation of diazoacetates and diazo anhydrides, which decompose to aryl radicals [76]. These additives were used in Meerwein arylation of isopropenyl acetate [77]. In our case, two

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

DNA display of glycoconjugates to emulate oligomeric interactions of glycans

• Alexandre Novoa and
• Nicolas Winssinger

Beilstein J. Org. Chem. 2015, 11, 707–719, doi:10.3762/bjoc.11.81

• density. Synthesis of glycoconjugate DNA by diazo-coupling. β-Galactose-modified deoxyuridine phosphoramidite used for solid-phase DNA synthesis and DNA display of glycan. (NHS)-carboxy-dT phosphoramidite as a general entry for the solid-phase synthesis of glycan–DNA conjugates. Preparation of the DNA

On the strong difference in reactivity of acyclic and cyclic diazodiketones with thioketones: experimental results and quantum-chemical interpretation

• Andrey S. Mereshchenko,
• Alexey V. Ivanov,
• Viktor I. Baranovskii,
• Grzegorz Mloston,
• Ludmila L. Rodina and
• Valerij A. Nikolaev

Beilstein J. Org. Chem. 2015, 11, 504–513, doi:10.3762/bjoc.11.57

• , Poland 10.3762/bjoc.11.57 Abstract The 1,3-dipolar cycloaddition of acyclic 2-diazo-1,3-dicarbonyl compounds (DDC) and thioketones preferably occurs with Z,E-conformers and leads to the formation of transient thiocarbonyl ylides in two stages. The thermodynamically favorable further transformation of C

• , carbocyclic diazodiketones are much less reactive under similar conditions due to the locked cyclic structure and are unfavorable for the 1,3-dipolar cycloaddition due to the Z,Z-conformation of the diazo molecule. This structure results in high, positive values of the Gibbs free energy change for the first

• stage of the cycloaddition process. Keywords: diazocarbonyl compounds; 1,3-dipolar cycloaddition; 1,3-oxathioles; thiiranes; thiocarbonyl ylides; thioketones; Introduction Dipolar cycloadditions of diazo compounds have been of great interest for a long time as they provide a means for the preparation

Azirinium ylides from α-diazoketones and 2H-azirines on the route to 2H-1,4-oxazines: three-membered ring opening vs 1,5-cyclization

• Nikolai V. Rostovskii,
• Mikhail S. Novikov,
• Alexander F. Khlebnikov,
• Galina L. Starova and
• Margarita S. Avdontseva

Beilstein J. Org. Chem. 2015, 11, 302–312, doi:10.3762/bjoc.11.35

• ring opening into atropoisomeric oxazolium betaines and cyclization. Azirinium ylides generated from 2,3-di- and 2,2,3-triaryl-substituted azirines give rise to only 2-azabuta-1,3-dienes and/or 2H-1,4-oxazines. Keywords: 2-azabuta-1,3-dienes; azirines; diazo compounds; nitrogen ylides; 2H-1,4-oxazines

• , rhodium carbenoids derived from α-diazocarbonyl compounds transform 2H-azirines 1 to azirinium ylides 5 (Scheme 1) which undergo facile N–C2 bond cleavage to give 2-azabuta-1,3-dienes 3. Recently we showed that the use of α-diazo-β-ketoesters 2 in these reactions, which are finished by 1,6-cyclization of

• 5-acyl-substituted 2H-1,4-oxazines. They could, in principle, be prepared from azirines and α-diazo ketones or 2-diazo-1,3-diketones via ring opening across the N–C2 bond in the intermediate azirinium ylides to form 2-azabuta-1,3-dienes and subsequent cyclization of the latter into 2H-1,4-oxazines

Three-component synthesis of C₂F₅-substituted pyrazoles from C₂F₅CH₂NH₂·HCl, NaNO₂ and electron-deficient alkynes

• Pavel K. Mykhailiuk

Beilstein J. Org. Chem. 2015, 11, 16–24, doi:10.3762/bjoc.11.3

• AS-136A [55]) (Scheme 3). Conclusion In summary, a novel approach to C2F5-substituted pyrazoles has been elaborated by a three-component reaction between C2F5CH2NH2·HCl, NaNO2 and electron-deficient alkynes. This method is highly practical: it does not require a) the pre-isolation of toxic diazo

Enantioselective synthesis of polyhydroxyindolizidinone and quinolizidinone derivatives from a common precursor

• Nemai Saha and
• Shital K. Chattopadhyay

Beilstein J. Org. Chem. 2014, 10, 3104–3110, doi:10.3762/bjoc.10.327

• other reasons, several novel methodologies have been developed towards the synthesis of polyhydroxylated indolizidine and quinolizidine derivatives as analogues of natural products which involved RCM [21][22][23][24], dipolar cycloaddition [25][26], nucleophilic substitution [27][28], diazo insertion

Isoxazolium N-ylides and 1-oxa-5-azahexa-1,3,5-trienes on the way from isoxazoles to 2H-1,3-oxazines

• Alexander F. Khlebnikov,
• Mikhail S. Novikov,
• Yelizaveta G. Gorbunova,
• Ekaterina E. Galenko,
• Kirill I. Mikhailov,
• Viktoriia V. Pakalnis and
• Margarita S. Avdontceva

Beilstein J. Org. Chem. 2014, 10, 1896–1905, doi:10.3762/bjoc.10.197

• Theoretical and experimental studies of the reaction of isoxazoles with diazo compounds show that the formation of 2H-1,3-oxazines proceeds via the formation of (3Z)-1-oxa-5-azahexa-1,3,5-trienes which undergo a 6π-cyclization. The stationary points corresponding to the probable reaction intermediates

• diazo esters with 5-alkoxyisoxazoles is a good approach to 1,4-di(alkoxycarbonyl)-2-azabuta-1,3-dienes. The reaction conditions for the preparation of aryl- and halogen-substituted 2H-1,3-oxazines and 1,4-di(alkoxycarbonyl)-2-azabuta-1,3-dienes from isoxazoles were investigated. Keywords: diazo esters

• ; isoxazoles; isoxazolium N-ylides; 2-azabuta-1,3-dienes; 2H-1,3-oxazines; Introduction Isoxazoles are versatile building blocks, which have found extensive use in organic synthesis [1][2][3]. However, reactions of isoxazoles with diazo compounds have scarcely been studied [1][2][3][4][5]. In 2008 Davies and