Thioester derivatives of the natural product psammaplin A as potent histone deacetylase inhibitors

• Matthias G. J. Baud,
• Thomas Leiser,
• Vanessa Petrucci,
• Mekala Gunaratnam,
• Stephen Neidle,
• Franz-Josef Meyer-Almes and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2013, 9, 81–88, doi:10.3762/bjoc.9.11

• ), 9 was inactive against A549 and WI38 cells at the highest concentration tested (50 μM). Similar to our previously reported SAR and mechanistic studies, a correlation between HDAC inhibition and cytotoxicity is clearly observable for these psammaplin A prodrugs. Notably, in enzyme assays, the

Flow photochemistry: Old light through new windows

• Jonathan P. Knowles,
• Luke D. Elliott and
• Kevin I. Booker-Milburn

Beilstein J. Org. Chem. 2012, 8, 2025–2052, doi:10.3762/bjoc.8.229

• , thus, gave data ideally suited to mechanistic studies [56]. The potential of microreactors in the photocatalytic splitting of water has also come under investigation. In this case a rhodium-containing inorganic photocatalyst was employed, and again online QMS permitted mechanistic studies to be

• conversion at the expense of increased dimer formation, both effects being ascribed to the greater average photon density in the flow system [70]. Mechanistic studies of the photoreduction of benzophenone (63) with benzhydrol (64) (Scheme 20) have been performed in a microflow reactor, allowing the quantum

Organocatalytic C–H activation reactions

• Subhas Chandra Pan

Beilstein J. Org. Chem. 2012, 8, 1374–1384, doi:10.3762/bjoc.8.159

• , radical anion 25, a strong reducing agent, transfers one electron to starting iodobenzene and results in the formation of biphenyl, potassium iodide and phenyl radical (Scheme 17). However, the role of the organocatalyst is still not fully understood at this point and detailed mechanistic studies are

Photoreactions of cyclic sulfite esters: Evidence for diradical intermediates

• Rick C. White,
• Benny E. Arney Jr. and
• Heiko Ihmels

Beilstein J. Org. Chem. 2012, 8, 1208–1212, doi:10.3762/bjoc.8.134

• considered. Keywords: diradicals; mechanisms; photochemistry; Introduction Photoinduced ring-opening or ring-fragmentation processes constitute an important type of reaction in organic photochemistry and have been examined both from a mechanistic and a synthetic point of view [1][2][3][4][5]. Mechanistic

• studies have revealed information on reactive intermediates, solvent effects, and stereochemical outcomes, while synthetic work has pointed to novel approaches for preparing various molecules. For example, deazetation reactions in solvents of increasing viscosity were employed to determine whether the

Control over molecular motion using the cis–trans photoisomerization of the azo group

• Estíbaliz Merino and
• María Ribagorda

Beilstein J. Org. Chem. 2012, 8, 1071–1090, doi:10.3762/bjoc.8.119

• mechanism is not well established. Several mechanistic studies have been performed on the isomerization reversal route cis→trans of azobenzene to investigate the effect of the substituents on the benzene rings as well as the influence of several parameters [24][25][26][27]. The available data suggest that

Bromine–lithium exchange: An efficient tool in the modular construction of biaryl ligands

• Laurence Bonnafoux,
• Frédéric R. Leroux and
• Françoise Colobert

Beilstein J. Org. Chem. 2011, 7, 1278–1287, doi:10.3762/bjoc.7.148

• method lacking both appeal and surprise [33], and only new applications of this reaction or mechanistic studies have been reported [30][32][33][45][46][47][48][49][50][51][52][53][54][55]. However, in the last few years, the halogen–metal permutation has recaptured its former role as one of the most

Triazole–Au(I) complex as chemoselective catalyst in promoting propargyl ester rearrangements

• Dawei Wang,
• Yanwei Zhang,
• Rong Cai and
• Xiaodong Shi

Beilstein J. Org. Chem. 2011, 7, 1014–1020, doi:10.3762/bjoc.7.115

• one of the most important reaction modes in the Au(I) promoted transformation [21][22][23][24][25][26][27][28][29][30][31]. Recent experimental and computational mechanistic studies revealed the 3,3-rearrangement to form the allene ester intermediate [32][33] as the key step in this transformation

Fine-tuning alkyne cycloadditions: Insights into photochemistry responsible for the double-strand DNA cleavage via structural perturbations in diaryl alkyne conjugates

• Wang-Yong Yang,
• Samantha A. Marrone,
• Nalisha Minors,
• Diego A. R. Zorio and
• Igor V. Alabugin

Beilstein J. Org. Chem. 2011, 7, 813–823, doi:10.3762/bjoc.7.93

• previous mechanistic studies suggested that neither singlet oxygen nor diffusing oxygen- and carbon-centered radical species play a significant role under the conditions where the most efficient ds cleavage by monoalkynes is observed (pH 6) [25]. From the narrowed list of mechanistic scenarios, base

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

• 24 to give 3-chromanol 25, which was reported by He and co-workers in 2004 (Scheme 8) [25]. The same year, Hashmi and co-workers described the first example of a gold-catalyzed conversion of alkynyl epoxides 26 into furans 27 [26][27]. Mechanistic studies performed later by Pale and co-workers [28

Construction of cyclic enones via gold-catalyzed oxygen transfer reactions

• Leping Liu,
• Bo Xu and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2011, 7, 606–614, doi:10.3762/bjoc.7.71

• cyclization of alkynyl ketones. Gold-catalyzed cyclization of terminal alkynyl ketones. Gold-catalyzed tandem oxygen transfer/Nazarov cyclizations. TfOH-mediated cyclization of alkynyl ketones. Gold-catalyzed cyclizations of 2-alkynyl-1,5-diketones. Designed isotopic labeling experiment for mechanistic

• studies. 18O isotopic experiments. B2PLYP/6-311+G(d,p)//B2PLYP/6-31G(d) computed reaction profile, relative energies in kcal/mol. Gold-catalyzed cyclization of tethered alkynyl arylaldehydes. Gold-catalyzed cyclization of terminal diynes. Proposed hydrolysis/cyclization mechanism. Gold-catalyzed

Kinetic evaluation of the solvolysis of isobutyl chloro- and chlorothioformate esters

• Malcolm J. D’Souza,
• Matthew J. McAneny,
• Dennis N. Kevill,
• Jin Burm Kyong and
• Song Hee Choi

Beilstein J. Org. Chem. 2011, 7, 543–552, doi:10.3762/bjoc.7.62

• –solvolysis of 4, points to strong rear-side nucleophilic solvation of the developing resonance-stabilized carbocation. Another useful tool for mechanistic studies is the l/m ratio. We have found [17] that values >2.7 are typical of solvolytic mechanisms proceeding by an addition–elimination pathway with the

An overview of the key routes to the best selling 5-membered ring heterocyclic pharmaceuticals

• Marcus Baumann,
• Ian R. Baxendale,
• Steven V. Ley and
• Nikzad Nikbin

Beilstein J. Org. Chem. 2011, 7, 442–495, doi:10.3762/bjoc.7.57

• (Scheme 35). Mechanistic studies showed that the related imidoyl compounds do not themselves undergo ring closure to form imidazoles and it was therefore proposed that the reaction between carbon tetrachloride and triphenylphosphine to generate dichlorotriphenylphosphorane and (dichloromethylene

Ene–yne cross-metathesis with ruthenium carbene catalysts

• Cédric Fischmeister and
• Christian Bruneau

Beilstein J. Org. Chem. 2011, 7, 156–166, doi:10.3762/bjoc.7.22

• performed using the first and second generation Grubbs (I, II) and Hoveyda (III, IV) catalysts (Figure 1). Concerning the catalytic cycles, several pathways have been proposed. Mechanistic studies based on kinetic measurements assisted or not with calculations have been carried out for both the intra- and

The allylic chalcogen effect in olefin metathesis

• Yuya A. Lin and
• Benjamin G. Davis

Beilstein J. Org. Chem. 2010, 6, 1219–1228, doi:10.3762/bjoc.6.140

• efficient ring-closing enyne metathesis of the acyclic starting material as the key cyclization step. Associated mechanistic studies suggested that the reaction proceeded via an “ene-then-yne” pathway, further suggesting that rate acceleration is likely due to the directing effect of the allylic hydroxy

Shelf-stable electrophilic trifluoromethylating reagents: A brief historical perspective

• Norio Shibata,
• Andrej Matsnev and
• Dominique Cahard

Beilstein J. Org. Chem. 2010, 6, No. 65, doi:10.3762/bjoc.6.65

• trifluoromethylating reagents. Since the initial report in 1984 this field has been increasingly active, however, there are still high challenges due to the current limitations of these reagents. A broader substrate scope is highly desirable in order to cover reactions of both hard and soft nucleophiles. Mechanistic

• studies with appropriate analytical tools should be conducted in order to obtain more insight on the transfer of the electrophilic CF3 group. A bimolecular nucleophilic substitution, SN2 type mechanism, is often suggested, although a single electron transfer mechanism cannot be ruled out depending on the

Pd-catalyzed decarboxylative Heck vinylation of 2-nitrobenzoates in the presence of CuF₂

• Lukas J. Gooßen,
• Bettina Zimmermann and
• Thomas Knauber

Beilstein J. Org. Chem. 2010, 6, No. 43, doi:10.3762/bjoc.6.43

• excess molecular sieves in NMP at 120 °C, yielding the vinyl arene 3aa in 89%. Based on our mechanistic studies of this and other decarboxylative couplings, we propose the mechanism detailed in Scheme 1. In the first step, the benzoate decarboxylates with formation of an aryl metal species. In contrast

From discovery to production: Scale- out of continuous flow meso reactors

• Peter Styring and
• Ana I. R. Parracho

Beilstein J. Org. Chem. 2009, 5, No. 29, doi:10.3762/bjoc.5.29

• more reagent to access the surface then the production slows. This is an interesting observation and we are undertaking detailed mechanistic studies in an attempt to clarify the situation. Another approach to increasing yield would be to increase the length of the reactor tubes. We standardised on 30