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

• unnamed rearrangement reactions of peroxides. It should be noted, that in the chemistry of peroxides two types of processes are considered under the term rearrangements. These are conventional rearrangements occurring with the retention of the molecular weight and transformations of one of the peroxide

• moieties after O–O-bond cleavage. Detailed information about the Baeyer−Villiger, Criegee, Hock, Kornblum−DeLaMare, Dakin, Elbs, Schenck, Smith, Wieland, and Story reactions is given. Unnamed rearrangements of organic peroxides and related processes are also analyzed. The rearrangements and related

• rearrangements and related processes play an important role in the chemistry of oxidation processes. Thus, the key reagent in the Sharpless epoxidation of allylic alcohols [48] and in the manufacture of propylene oxide via the Prilezhaev reaction [49][50][51] is tert-butyl hydroperoxide. In industry, phenol and

Biosynthesis of oxygen and nitrogen-containing heterocycles in polyketides

• Franziska Hemmerling and
• Frank Hahn

Beilstein J. Org. Chem. 2016, 12, 1512–1550, doi:10.3762/bjoc.12.148

• annelated with a δ-lactone and a cyclopentanone or oxidation products of the latter. Aflatoxin biosynthesis has been studied since the late 1960s and has attracted attention, because the polyketide undergoes a series of oxidative rearrangements, which drastically alter the molecular scaffold. Due to the

• synthase (NorS) (Scheme 16) [83][85]. NorS is a complex of a NR-PKS PksA and a pair of yeast-like fatty acid synthases HexA/HexB, which provide an unusual hexanoyl-CoA starter unit [86]. Norsolorinic acid (100) undergoes three oxidative rearrangements towards aflatoxin B1 (94): The first rearrangement sets

Ring-whizzing in polyene-PtL₂ complexes revisited

• Oluwakemi A. Oloba-Whenu,
• Thomas A. Albright and
• Chirine Soubra-Ghaoui

Beilstein J. Org. Chem. 2016, 12, 1410–1420, doi:10.3762/bjoc.12.135

• ; density functional theory (DFT); hapototropic rearrangements; HOMO–LUMO interactions; polyene-ML2 complexes; ring-whizzing; Introduction Polyene–transition metal complexes were found to undergo fluxional rearrangements as early as 1956 with the preparation of Cp2Fe(CO)2 [1]. The migration of an MLn unit

• around the periphery of a cyclic polyene is commonly called ring-whizzing, purportedly ascribed to Rowland Pettit [2]. A more inclusive term is haptotropic rearrangement [3] wherein a metal atom changes its hapticity along the reaction path. Haptotropic rearrangements in ML3 and MCp complexes are

• of us undertook a theoretical survey of these compounds at the extended Hückel level a number of years ago [20][21]. In the present contribution we shall revisit some of these rearrangements using DFT theory, as well as, investigate some new compounds. A d10 ML2 fragment possesses a high-lying HOMO

The EIMS fragmentation mechanisms of the sesquiterpenes corvol ethers A and B, epi-cubebol and isodauc-8-en-11-ol

• Patrick Rabe and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2016, 12, 1380–1394, doi:10.3762/bjoc.12.132

• isolated from the producing organism. Deuterium labellings also allow to follow hydrogen rearrangements, but non-specific hydrogen migrations during the fragmentation process and kinetic isotope effects can make data interpretation difficult. In contrast, the introduction of 13C-labelling into a terpene

• yield C1+ that upon hydrogen rearrangements via D1+ to E1+ and inductive cleavage of water results in the conjugated cation F1+. Since the 13C-labelling experiments presented in this study cannot distinguish which of the hydrogens of 1 are rearranged or lost, alternative mechanisms may contribute to the

• +·, followed by an inductive cleavage with neutral loss of isobutyraldehyde to H2+·. This reactive intermediate can stabilise to the conjugated radical cations I2+· or J2+· by two alternative hydrogen rearrangements. PMA135 for the base peak ion m/z = 135 reveals that this fragment ion is produced from C1–C9

Strecker degradation of amino acids promoted by a camphor-derived sulfonamide

• M. Fernanda N. N. Carvalho,
• M. João Ferreira,
• Ana S. O. Knittel,
• Maria da Conceição Oliveira,
• João Costa Pessoa,
• Rudolf Herrmann and
• Gabriele Wagner

Beilstein J. Org. Chem. 2016, 12, 732–744, doi:10.3762/bjoc.12.73

• types of reactions include the alkylation of the imine nitrogen atom followed by ring annulation [6], cleavage of the sulfonimine [7][8] or camphor [9] rings, reduction of the CO or CN double bonds [10], addition of acetylide anions to form dialkynes that can undergo complex skeletal rearrangements and

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• these aspects of reaction mechanisms. Unique potential energy surface topologies associated with these rearrangements have been discovered in recent years that are not only of fundamental interest, but also provide insight into the way Nature manipulates chemical space to accomplish specific chemical

• transformations. Cautions for analyzing both experimental and theoretical data on carbocation rearrangements are included throughout. Keywords: carbocation; density functional theory; dynamics; mechanism; terpene; Review Introduction to terpene forming carbocation rearrangements Terpene natural products display

• commonly used [35][36][37][38][39][40]. In particular, the B3LYP and mPW1PW91 functionals, along with small to medium sized basis sets have seen the most use in studying carbocation rearrangements of relevance to biosynthesis [6]. Using molecular dynamics trajectories to rationalize experimental results is

Study on the synthesis of the cyclopenta[f]indole core of raputindole A

• Nils Marsch,
• Mario Kock and
• Thomas Lindel

Beilstein J. Org. Chem. 2016, 12, 334–342, doi:10.3762/bjoc.12.36

• ketone 26 proceeded in the highest yield of all our Meyer–Schuster rearrangements. With triflated α,β-unsaturated ketone 26 in hand, we attempted reductive Heck cyclizations to the raputindole core structure. For instance, we employed Pd(dba)2 (12 mol %), QPhos (24 mol %), and NEt3 (1.20 equiv) in DMF at

Tandem processes promoted by a hydrogen shift in 6-arylfulvenes bearing acetalic units at ortho position: a combined experimental and computational study

• Mateo Alajarin,
• Marta Marin-Luna,
• Pilar Sanchez-Andrada and
• Angel Vidal

Beilstein J. Org. Chem. 2016, 12, 260–270, doi:10.3762/bjoc.12.28

• construction of diverse fused ring systems. Other classical pericyclic processes that may potentially occur in fulvene fragments (electrocyclic and ene reactions, sigmatropic rearrangements and shifts) have received less attention, most probably with the only exception of the Claisen rearrangement [16

Aggregation behavior of amphiphilic cyclodextrins in a nonpolar solvent: evidence of large-scale structures by atomistic molecular dynamics simulations and solution studies

• Giuseppina Raffaini,
• Fabio Ganazzoli and
• Antonino Mazzaglia

Beilstein J. Org. Chem. 2016, 12, 73–80, doi:10.3762/bjoc.12.8

• systems with a total of sixty-four molecules produced significant rearrangements with the formation of extended structures with a long-range connectivity due to intermolecular non-bonded interactions again reproducing those previously mentioned. The first of these extended structures is shown in Figure 5

Synthesis of Xenia diterpenoids and related metabolites isolated from marine organisms

• Tatjana Huber,
• Lara Weisheit and
• Thomas Magauer

Beilstein J. Org. Chem. 2015, 11, 2521–2539, doi:10.3762/bjoc.11.273

• commonly employed method for the synthesis of cyclononenes due to the predictability of the stereochemical outcome of the product. The construction of cyclononenes can furthermore be achieved by thermal [3,3]-sigmatropic rearrangements of 1,5-dienes C. When the reaction proceeds via a chairlike transition

• , several strategies for the preparation of the characteristic nine-membered carbocyclic ring structures have been developed. The synthetic strategies are typically based on ring expansion (Grob-type fragmentation and sigmatropic rearrangements), ring closing (metathesis and transition metal-catalyzed

Recent highlights in biosynthesis research using stable isotopes

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271

• rearrangements and cyclizations experimentally. The structure elucidation of terpenoids can be challenging because of the multicyclic carbon skeletons with several contiguous stereocenters. The assistance of 13C labels can in such cases be especially helpful, and if completely 13C-labeled carbon backbones can be

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

• Giuseppina Raffaini,
• Antonino Mazzaglia and
• Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

• equilibration criteria, the MD runs were carried out for different lengths. The simulations in explicit water were often shorter than in vacuo due to the much larger computational burden of a fully hydrated system, so that much lengthier rearrangements cannot be ruled out. On the other hand, system

• allow for possible major rearrangements of the two molecules, as indeed found in the fully optimized geometries shown in Figure 6 at left. In particular, the H–H and H–P initial arrangements display an almost complete rotation and/or a noticeable tilt of one molecule with respect to the other one

• arrangements of the two aCD (or more precisely in the distance between the centers of mass of the two aCD), which can require a longer simulation time to achieve equilibrium by small local rearrangements than potential energy. Accordingly, the initial interaction geometry kinetically traps the adducts in a

Copper-mediated synthesis of N-alkenyl-α,β-unsaturated nitrones and their conversion to tri- and tetrasubstituted pyridines

• Dimitra Kontokosta,
• Daniel S. Mueller,
• Dong-Liang Mo,
• Wiktoria H. Pace,
• Rachel A. Simpson and
• Laura L. Anderson

Beilstein J. Org. Chem. 2015, 11, 2097–2104, doi:10.3762/bjoc.11.226

• Liebeskind and coworkers due to its modularity and control of regioselectivity and wondered if a Chan–Lam route to N-alkenylnitrones would allow us to prepare similar intermediates (Scheme 2A) [51]. Nakamura and coworkers have reported that N-allenylnitrones can be accessed through rearrangements of O

Structure and conformational analysis of spiroketals from 6-O-methyl-9(E)-hydroxyiminoerythronolide A

• Ana Čikoš,
• Irena Ćaleta,
• Dinko Žiher,
• Mark B. Vine,
• Ivaylo J. Elenkov,
• Marko Dukši,
• Dubravka Gembarovski,
• Marina Ilijaš,
• Snježana Dragojević,
• Ivica Malnar and
• Sulejman Alihodžić

Beilstein J. Org. Chem. 2015, 11, 1447–1457, doi:10.3762/bjoc.11.157

• spectroscopy and molecular modelling. The reaction kinetics and mechanistic aspects of this transformation are discussed. These rearrangements provide a facile synthesis of novel macrolide scaffolds. Keywords: configuration; conformation; 6-O-methyl-9(E)-hydroxyiminoerythronolide A; reaction mechanism

Novel carbocationic rearrangements of 1-styrylpropargyl alcohols

• Christine Basmadjian,
• Fan Zhang and
• Laurent Désaubry

Beilstein J. Org. Chem. 2015, 11, 1017–1022, doi:10.3762/bjoc.11.114

• article, we demonstrate the delicate balance among several mechanistic pathways by a minor change of substrate in acid-catalyzed rearrangements of 1-styrylpropargyl alcohols. Indeed, these compounds may generate a furan (18), an enone (19), an allylic ether or even a naphthalenone (17). The formation of

• 16. Optimization of the acid-catalyzed rearrangements of enynol 2. Supporting Information Supporting Information File 218: Experimental procedures for the synthesis of compounds 7–9, 13, 14 and 17–28. Acknowledgements L.D. was supported by the "Association pour la Recherche sur le Cancer" (ARC). We

Further exploration of the heterocyclic diversity accessible from the allylation chemistry of indigo

• Alireza Shakoori,
• John B. Bremner,
• Mohammed K. Abdel-Hamid,
• Anthony C. Willis,
• Rachada Haritakun and
• Paul A. Keller

Beilstein J. Org. Chem. 2015, 11, 481–492, doi:10.3762/bjoc.11.54

• ' reagent. This is not unexpected as there are reports of ruthenium-based species catalysing Claisen rearrangements [7] including a similar RCM–Claisen sequence in 2,2'-bis(allyloxy)-1,1'-binaphthyls and O,O'-(but-2-en-1,4-diyl) binaphthols [12][13]. Additionally, examples of C2 to C3 Claisen rearrangement

An unusually stable chlorophosphite: What makes BIFOP–Cl so robust against hydrolysis?

• Roberto Blanco Trillo,
• Jörg M. Neudörfl and
• Bernd Goldfuss

Beilstein J. Org. Chem. 2015, 11, 313–322, doi:10.3762/bjoc.11.36

• , in Pd catalysts. Keywords: chirality; hydrolysis; phosphorus; rearrangements; terpenoids; Introduction Phosphorus halides are highly reactive intermediates for the synthesis of phosphites and phosphoramidites [1][2][3][4][5], which are widely used, for example, as ligands in catalysts [6][7][8][9

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

• Laurence Burroughs,
• John Ritchie,
• Mkhethwa Ngwenya,
• Dilfaraz Khan,
• William Lewis and
• Simon Woodward

Beilstein J. Org. Chem. 2015, 11, 273–279, doi:10.3762/bjoc.11.31

• via nominal [3,3]-sigmatropic rearrangements of xanthates. As the thiocarbamate products derived from these are predicted to be easily hydrolised to thiolates this potentially offers a simple route to a protected SH analogue of 3. Lin’s chemistry [14] cannot be used as no simple method to modify SOPh

• to SH is available. We proposed that use of starting material xanthate 1c should provide suitably protected 5-thiotetracene derivatives directly (Scheme 2). The required [3,3]-sigmatropic rearrangements and subsequent 6π elecrocyclisations of 1c have precise stereochemical requirements (Scheme 2

• , the possibility of aromatisation of 6 through Chugaev [22] syn elimination. Finally the system of Scheme 2 provides a unique opportunity to probe if these rearrangements do indeed proceed from the neutral xanthates 1c or via the previously unprecedented 1d–2d–6d anionic cascades. Results and

Anomalous diffusion of Ibuprofen in cyclodextrin nanosponge hydrogels: an HRMAS NMR study

• Monica Ferro,
• Franca Castiglione,
• Carlo Punta,
• Lucio Melone,
• Walter Panzeri,
• Barbara Rossi,
• Francesco Trotta and
• Andrea Mele

Beilstein J. Org. Chem. 2014, 10, 2715–2723, doi:10.3762/bjoc.10.286

• structure of the CDNSEDTA 1:8 is expected to show a high degree of heterogeneity in the distribution of pores, due to rearrangements caused by the steric hindrance. The TEM image of Figure 4b shows the details of the pores heterogeneity and the sponge-like morphology. The slightly superdiffusive behaviour

Photorelease of phosphates: Mild methods for protecting phosphate derivatives

• Sanjeewa N. Senadheera,
• Abraham L. Yousef and
• Richard S. Givens

Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212

• modest efficiency, Φ = 0.028. Similarly, the methoxy analog, 1,4-MNA DEP (14b), released DEP, but with a much lower efficiency (Φ = 0.0078). Both quantitatively produced DEP and, pleasingly, underwent photo-Favorskii rearrangements converting the aryl ketones to methyl naphthylacetates, blue-shifting the

• byproduct chromophore absorptions. Both 14a and 14b now become the first new examples of photo-Favorskii rearrangements, here on a naphthyl platform. Previous examples are limited to phenacyl frameworks [6][7][8][9][15][38][39]. It is interesting to note, however, that replacement of the OH with OMe in the

• cyclization to form the ‘Favorskii intermediate’ 33 [6][8][15][26][38][39][48]. In contrast to the 1,4-naphthyl design, neither 10 nor 24 underwent Favorskii rearrangements. While both gave stoichiometric release of DEP, the chromophores either remain intact (for 10) as also reported for other 2

Synthesis of 2-substituted tryptophans via a C3- to C2-alkyl migration

• Michele Mari,
• Simone Lucarini,
• Francesca Bartoccini,
• Giovanni Piersanti and
• Gilberto Spadoni

Beilstein J. Org. Chem. 2014, 10, 1991–1998, doi:10.3762/bjoc.10.207

• the corresponding pyrrolindoline derivative without any trace of the rearranged 2-substituted tryptophan, even with extended reaction times. The electronic properties of the migratory group have a pronounced effect on the reaction profile. As known from other Wagner–Meerwein-type rearrangements [71

Application of cyclic phosphonamide reagents in the total synthesis of natural products and biologically active molecules

• Thilo Focken and
• Stephen Hanessian

Beilstein J. Org. Chem. 2014, 10, 1848–1877, doi:10.3762/bjoc.10.195

• products or bioactive molecules will be discussed [10]. Similar technologies to the ones discussed here without such applications and other uses of chiral phosphonamide reagents in asymmetric synthesis such as Denmark’s carbanion-accelerated Claisen rearrangements [11][12] have been reviewed elsewhere [13

cis–trans Isomerization of silybins A and B

• Michaela Novotná,
• Radek Gažák,
• David Biedermann,
• Florent Di Meo,
• Petr Marhol,
• Marek Kuzma,
• Lucie Bednárová,
• Kateřina Fuksová,
• Patrick Trouillas and
• Vladimír Křen

Beilstein J. Org. Chem. 2014, 10, 1047–1063, doi:10.3762/bjoc.10.105

• (compared to O-9) by 4 kcal·mol−1. The coordination with boron initiates isomerization at C-2, C-3 and C-10, C-11 by charge rearrangements (e.g., proton release and formation of IIb in Scheme 5). The mechanisms related to both sites can be considered separately, as both moieties are electronically

• BF3 complexation as confirmed by the complexation energies (Table 3). Following complexation, the D-ring opening proceeds (Scheme 6), allowing molecular rearrangements and isomerization after ring closure. The observation of the isomerization of 1 (or 2) at C-11 that occurs in EtOAc but not in DMF can

Dimerisation, rhodium complex formation and rearrangements of N-heterocyclic carbenes of indazoles

• Zong Guan,
• Jan C. Namyslo,
• Martin H. H. Drafz,
• Martin Nieger and
• Andreas Schmidt

Beilstein J. Org. Chem. 2014, 10, 832–840, doi:10.3762/bjoc.10.79

• -ylidene with acetylenes. Indazol-3-ylidenes which possess an aryl ring at N1 rearrange to give substituted acridines by a ring-cleavage/pericyclic ring-closure reaction sequence (2→A→B→11) (Scheme 3). It proved to be advantageous to start these rearrangements from indazolium salts which are readily

• available by copper-catalyzed aryl couplings or Buchwald–Hartwig reactions [22]. Pyrazol-3-ylidenes rearrange similarly to quinolines [17]. We report here on two unexpected rearrangements of indazol-3-ylidene, and trapping reactions of the N-heterocyclic carbene with rhodium. Results and Discussion On

• : C51H42N2OP2Rh calcd for 863.1827; found: 863.1827. General procedure for the rearrangements of the indazole carbene dimers to 16 A solution of 1.0 mmol of the dimers of the indazole carbenes 13a/13b/13d in 20 mL of xylene was stirred at reflux temperature for 3 hours. After the solvent was distilled off in

The Flögel-three-component reaction with dicarboxylic acids – an approach to bis(β-alkoxy-β-ketoenamides) for the synthesis of complex pyridine and pyrimidine derivatives

• Mrinal K. Bera,
• Moisés Domínguez,
• Paul Hommes and
• Hans-Ulrich Reissig

Beilstein J. Org. Chem. 2014, 10, 394–404, doi:10.3762/bjoc.10.37

• β-ketoenamides 14 and 20 with hydroxylamine hydrochloride to pyridine-N-oxides 28 and 30 and their subsequent Boekelheide rearrangements furnishing functionalized bis(pyrimidine) derivative 29 and pyrimidine/pyridine conjugate 31. Riley oxidation of bis(pyrimidine) derivative 23a and conversion of