Cationic Pd(II)-catalyzed C–H activation/cross-coupling reactions at room temperature: synthetic and mechanistic studies

• Takashi Nishikata,
• Alexander R. Abela,
• Shenlin Huang and
• Bruce H. Lipshutz

Beilstein J. Org. Chem. 2016, 12, 1040–1064, doi:10.3762/bjoc.12.99

• temperature. In this account we disclose, in addition to full details associated with this C–H activation chemistry, additional applications of room temperature Fujiwara–Moritani reactions including a synthesis of the herbicide boscalid, as well as spectroscopic and mechanistic studies. Results and Discussion

• favorably with all known routes to this pesticide shown in Scheme 6 [86][208][209][210][211][212][213]. Mechanistic insight Although there have been a number of mechanistic studies on C–H activation reactions involving neutral palladium species [34][108][109][110][111][112][113][114][115][116][117][118][119

Catalytic asymmetric synthesis of biologically important 3-hydroxyoxindoles: an update

• Bin Yu,
• Hui Xing,
• De-Quan Yu and
• Hong-Min Liu

Beilstein J. Org. Chem. 2016, 12, 1000–1039, doi:10.3762/bjoc.12.98

• diastereoselectivities (all >95:5 dr) and enantioselectivities (up to >99% ee, Scheme 58) [75]. Mechanistic studies showed that this cascade reaction proceeded via a vinylogous Michael addition/Friedel–Crafts process involving a dual H-bonding activation of substrates. In 2015, Wang and co-workers reported Lewis acid

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

• . Carbene cascade for fused bicycles. Cascade formation of bridged rings. Conformational effects. Hydrazone cascade reaction. Mechanistic studies. Gold carbene formation from alkynes. Au-catalyzed bridged-bicycle formation. Gold carbene/alkyne cascade. Gold carbene/alkyne cascade with C–H bond insertion

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

• is an important tool for the synthesis of complex molecules due to the high control of enantioselectivity in the formation of stereogenic centers. This paper presents a brief review of the early issues, related mechanistic studies and recent applications on this chemistry area. Keywords: C–H

(Thio)urea-mediated synthesis of functionalized six-membered rings with multiple chiral centers

• Giorgos Koutoulogenis,
• Nikolaos Kaplaneris and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2016, 12, 462–495, doi:10.3762/bjoc.12.48

• reaction between malonitirile 184 and substituted aromatic imine 185 catalyzed by bifunctional thiourea 88 (Scheme 60) [81]. Many functional groups were tolerated, obtaining the desired densely functionalized tetrahydroquinolines 186. Additional mechanistic studies by the authors strongly suggest the

• to be employed in order to obtain spiro-dihydropyran-oxindole derivatives 231 in good to excellent yields, using catalyst 232 (Scheme 72) [91]. The mechanistic studies showed that the 3,5-bis(trifluoromethyl)phenyl group was an essential component of the thiourea catalyst. After the optimization of

Enantioselective [3 + 2] annulation of α-substituted allenoates with β,γ-unsaturated N-sulfonylimines catalyzed by a bifunctional dipeptide phosphine

• Huanzhen Ni,
• Weijun Yao and
• Yixin Lu

Beilstein J. Org. Chem. 2016, 12, 343–348, doi:10.3762/bjoc.12.37

• reactions yielded highly functionalized cyclopentenes with an all-carbon quaternary center in moderate to good yields and good to excellent enantioselectivities. Further extension of the reaction reported herein and mechanistic studies are ongoing in our laboratory. Experimental General procedure for the [3

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• high levels of enantioselectivity. This lack is likely due to the multiple possibilities for copper acetylide structures (monomer, dimer, dicopper acetylide, etc.) [18][59][60][61][62][63][64][65]. Careful mechanistic studies to elucidate the structures of chiral copper acetylides and to provide

Iron complexes of tetramine ligands catalyse allylic hydroxyamination via a nitroso–ene mechanism

• David Porter,
• Belinda M.-L. Poon and
• Peter J. Rutledge

Beilstein J. Org. Chem. 2015, 11, 2549–2556, doi:10.3762/bjoc.11.275

• is a trickier proposition [14], although this has been demonstrated in an intramolecular context [22]. Mechanistic studies Previous studies of iron-promoted allylic amination reactions with N-phenylhydroxylamine, and copper-catalysed reactions with N-Boc-hydroxylamine (8) return regio- and

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

• in the literature. In addition, recent mechanistic studies have focused on the rationalization of nitrogen-induced catalysts deactivation. The purpose of this mini-review is to give a brief overview of successful metathesis reactions involving olefins containing N-heteroaromatics in order to

• especially as a simple chlorine substituent is sufficient to allow the metathesis to proceed (Table 5). Conclusion N-Heteroaromatics are known to have a deleterious impact on metathesis by inducing ruthenium catalysts deactivation. Based on NMR and kinetic mechanistic studies, Lewis and/or Brønsted basicity

Molecular-oxygen-promoted Cu-catalyzed oxidative direct amidation of nonactivated carboxylic acids with azoles

• Wen Ding,
• Shaoyu Mai and
• Qiuling Song

Beilstein J. Org. Chem. 2015, 11, 2158–2165, doi:10.3762/bjoc.11.233

• scope. The mechanistic studies reveal that oxygen plays an essential role in the success of the amidation reactions with copper peroxycarboxylate as the key intermediate. Transamidation occurs smoothly between azole amide and a variety of amines. Keywords: amidation; azoles; Cu-catalyzed; molecular

Computational study of productive and non-productive cycles in fluoroalkene metathesis

• Markéta Rybáčková,
• Jan Hošek,
• Ondřej Šimůnek,
• Viola Kolaříková and
• Jaroslav Kvíčala

Beilstein J. Org. Chem. 2015, 11, 2150–2157, doi:10.3762/bjoc.11.232

• valuable in the study of reaction mechanisms. In particular, the use of time-efficient DFT methods for the theoretical study of alkene metathesis has been extensively reviewed [9][10][11] and computational results have been found to agree well with recent experimental mechanistic studies based on easily

C–H bond halogenation catalyzed or mediated by copper: an overview

• Wenyan Hao and
• Yunyun Liu

Beilstein J. Org. Chem. 2015, 11, 2132–2144, doi:10.3762/bjoc.11.230

• modified catalytic conditions (Scheme 11). However, it was found that the oxidative bromination of phenols exhibited generally lower para regioselectivity than the corresponding chlorination [49]. Mechanistic studies on these reactions indicated that the halogenation reactions proceeded via a free radical

Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

• David W. Manley and
• John C. Walton

Beilstein J. Org. Chem. 2015, 11, 1570–1582, doi:10.3762/bjoc.11.173

• discoveries of SCPC mediated bond forming processes Several investigations during the 80s and early 90s demonstrated that bond forming organic transformations could be accomplished using SCPC [30][31][32][33][34], but these were mainly spectroscopic and/or mechanistic studies on the formation of well-known

Surprisingly facile CO₂ insertion into cobalt alkoxide bonds: A theoretical investigation

• Willem K. Offermans,
• Claudia Bizzarri,
• Walter Leitner and
• Thomas E. Müller

Beilstein J. Org. Chem. 2015, 11, 1340–1351, doi:10.3762/bjoc.11.144

• feasible. In mechanistic studies on zinc dicarboxylates and their application in the heterogeneously catalysed copolymerisation of CO2 and epoxides a bimetallic mechanism was proposed [31]. As post-modification of the prepared catalysts with water proved to be important for the activity of the catalysts

Are D-manno-configured Amadori products ligands of the bacterial lectin FimH?

• Tobias-Elias Gloe,
• Insa Stamer,
• Cornelia Hojnik,
• Tanja M. Wrodnigg and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2015, 11, 1096–1104, doi:10.3762/bjoc.11.123

• potential as therapeutics and as tools for mechanistic studies in biology. This is because they are not sensitive towards enzymatic hydrolysis such as in physiological environment, in contrast to the naturally occurring O- and N-glycosides. With respect to our long-lasting interest in the design and

Radical-mediated dehydrative preparation of cyclic imides using (NH₄)₂S₂O₈–DMSO: application to the synthesis of vernakalant

• Dnyaneshwar N. Garad,
• Subhash D. Tanpure and
• Santosh B. Mhaske

Beilstein J. Org. Chem. 2015, 11, 1008–1016, doi:10.3762/bjoc.11.113

• /unsubstituted aromatic amines and unsaturated anhydridesa. Imides from aliphatic amines and saturated anhydridesa. Supporting Information Supporting Information File 116: Experimental details, characterization data, copies of NMR spectra of all compounds and the details of mechanistic studies

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

• the possibility for variations outside these complex sequences, for example the radical-induced 1,3-shift of a cinnamyl moiety, likely to occur at a point buried within the mechanistic mix illustrated in Scheme 9. Clearly, further mechanistic studies will be required to continue to explain the

A procedure for the preparation and isolation of nucleoside-5’-diphosphates

• Heidi J. Korhonen,
• Hannah L. Bolt and
• David R. W. Hodgson

Beilstein J. Org. Chem. 2015, 11, 469–472, doi:10.3762/bjoc.11.52

• synthesis; nucleic acids; nucleoside-5’-diphosphate; phosphorylation; Introduction Nucleoside-5'-phosphates are key to many mechanistic studies and chemical biology applications [1][2][3]. Synthetic approaches towards nucleoside-5'-phosphates are well-established [4], however, the methods tend to be

Cross-dehydrogenative coupling for the intermolecular C–O bond formation

• Igor B. Krylov,
• Vera A. Vil’ and
• Alexander O. Terent’ev

Beilstein J. Org. Chem. 2015, 11, 92–146, doi:10.3762/bjoc.11.13

Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

• Matthieu Jouffroy,
• Rafael Gramage-Doria,
• David Sémeril,
• Dominique Armspach,
• Dominique Matt,
• Werner Oberhauser and
• Loïc Toupet

Beilstein J. Org. Chem. 2014, 10, 2388–2405, doi:10.3762/bjoc.10.249

• coupling catalysts [72]. The relatively low performance of WIDEPHOS, when operating as a bis(monodentate) ligand, is probably the result of the severe steric encumbrance generated within the cavity of the postulated dinuclear complex. According to a number of mechanistic studies, the structure of the

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

• organic chemistry and biochemistry, but they are particularly important for mechanistic studies in biochemistry and biophysics [6][8][9][10][11]. Most PPG candidates require sufficiently high energy excited states for heterolysis of a carbon–oxygen or carbon–heteroatom bond that binds the chromophore to a

• attempted to circumvent or avoid the inherent deficiencies of the classical o-NB, benzoin, and coumaryl analogs (see Figure 1). A noisome limitation of o-NB PPGs that mitigate their general use in biological and mechanistic studies are their inherently slow reaction rates. o-NB rate constants are decidedly

A new charge-tagged proline-based organocatalyst for mechanistic studies using electrospray mass spectrometry

• J. Alexander Willms,
• Rita Beel,
• Martin L. Schmidt,
• Christian Mundt and
• Marianne Engeser

Beilstein J. Org. Chem. 2014, 10, 2027–2037, doi:10.3762/bjoc.10.211

• -ethylpyridinium-4-phenoxy substituent has been synthesized with the aim of facilitating mechanistic studies of proline-catalyzed reactions by ESI mass spectrometry. The charged residue ensures a strongly enhanced ESI response compared to neutral unmodified proline. The connection by a rigid linker fixes the

• as a function of time [8] and beyond that a characterization of transient intermediates by tandem mass spectrometry. ESI mass-spectrometric mechanistic studies have been reported for a broad range of reaction types ranging from transition metal-catalyzed polymerization [6][9] and coupling reactions

• , mechanistic studies on organocatalytic reactions [31][32][33][34][35][36][37][38] using ESI mass spectrometry [20][39][40][41][42][43][44][45][46][47][48][49] have been reported. The pioneering studies of List and Barbas [50] revealed that the amino acid L-proline is an effective catalyst for a great variety

Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications

• Mahesh K. Lakshman,
• Manish K. Singh,
• Mukesh Kumar,
• Raghu Ram Chamala,
• Vijayender R. Yedulla,
• Domenick Wagner,
• Evan Leung,
• Lijia Yang,
• Asha Matin and
• Sadia Ahmad

Beilstein J. Org. Chem. 2014, 10, 1919–1932, doi:10.3762/bjoc.10.200

• mechanistic details would be required. Thus, the next stage in these investigations focused on this aspect. Mechanistic studies Our investigations began with the reactions of BOP. We reasoned that among the three pathways shown in Scheme 2, 31P{1H} NMR may allow for distinguishing pathway a from b and c. Thus

• alkyl halides or more cumbersome methods. Mechanistic studies indicate that reactions of alcohols with these peptide-coupling reagents, in the presence of a base, appear to proceed by formation of alcohol phosphonium derivatives (with BOP), or alcohol tosylates (with Bt-OTs), and not through direct

Pd/C-catalyzed aerobic oxidative esterification of alcohols and aldehydes: a highly efficient microwave-assisted green protocol

• Marina Caporaso,
• Giancarlo Cravotto,
• Spyros Georgakopoulos,
• George Heropoulos,
• Katia Martina and
• Silvia Tagliapietra

Beilstein J. Org. Chem. 2014, 10, 1454–1461, doi:10.3762/bjoc.10.149

• esterification has not still been fully elucidated. Additional mechanistic studies will be needed to support a mechanistic rationale. Conclusion In summary, we have described a highly efficient, versatile and eco-friendly protocol for the aerobic esterification of benzylic alcohols and aldehydes to methyl esters

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• various applications of eosin Y to visible light-driven syntheses of biaryls [15], stilbenes [16], benzothiophenes [17], α-phenylketones [18], phenanthrenes [19], arylsulfides [20] and arylboron pinacolates [21] (Scheme 1). Numerous mechanistic studies have been performed at reactions with organometallic