[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• energy gap), for type III (LUMO-controlled) combining a low-lying dipole LUMO and a dipolarophile HOMO where substituent effects are completely opposite. For type II cycloadditions in which two-way interactions between the dipole HOMO and the dipolarophile LUMO or the dipole LUMO and the dipolarophile

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

• benzo[7]annulenes 123–128 were prepared using 4,5-benzotropone (11) as starting material and 1H and 13C NMR studies in each series of compounds revealed strikingly different substituent effects (Scheme 21). In order to perform reactions with alkyl Grignard reagents, Bertelli’s group realized the

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P^® activation of 3-arylpropiolic acids

• Melanie Denißen,
• Alexander Kraus,
• Guido J. Reiss and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 2340–2351, doi:10.3762/bjoc.13.231

• substituent effects in the electronic ground and excited states (see Table S6 in Supporting Information File 1). Although the linear correlations of λmax,abs with all σ parameters are relatively poor, the correlations of λmax,em with σR and σp+ indicate a strong influence of resonance stabilization in the

Phosphorus pentasulfide mediated conversion of organic thiocyanates to thiols

• Chandra Kant Maurya,
• Avik Mazumder and
• Pradeep Kumar Gupta

Beilstein J. Org. Chem. 2017, 13, 1184–1188, doi:10.3762/bjoc.13.117

• of electron withdrawing halogens on the phenyl ring diminished the rate of reaction. It was interesting to note that in this reaction, product yields were found to be less susceptible to substituent effects in comparison to the reaction rates. One of the noticeable features of the present method is

Application of heterocyclic aldehydes as components in Ugi–Smiles couplings

• Katelynn M. Mason,
• Michael S. Meyers,
• Abbie M. Fox and
• Sarah B. Luesse

Beilstein J. Org. Chem. 2016, 12, 2032–2037, doi:10.3762/bjoc.12.191

• –Smiles product 2i without observation of cyclized product 1b. For heterocyclic aldehydes, allylamine generally provided the most efficient amine coupling partner, but a range of simple amines were competent components in this reaction. Computational studies of substituent effects in the Ugi–Smiles

Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

• Lucie Brulíková,
• Aidan Harrison,
• Marvin J. Miller and
• Jan Hlaváč

Beilstein J. Org. Chem. 2016, 12, 1949–1980, doi:10.3762/bjoc.12.184

• derivative 47 or the chloronitroso derivative 49, which gave the distal isomer 48 or proximal isomer 50, respectively. In disubstituted dienes, the substituent effects were found to be additive, and predictions can be made based on the relative position and strength of the electron-withdrawing or donating

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

• therefore set out to study the thermal stabilities of 2a–c by using kinetic data and thus obtaining information of substituent effects. Results and Discussion Kinetic measurements We synthesized the ethyl halodiazoacetates 2a–c as outlined in Scheme 1 and measured their concentrations vs time in different

• only 8 kcal/mol for EDA (Figure 3). The π-donation ability from the halo substituents to provide carbene stabilization follows the order F > Cl > Br and presumably I as the least stabilizing carbene substituent [20]. The thermal stabilities of ethyl halodiazoacetates and their α-substituent effects are

Is conformation a fundamental descriptor in QSAR? A case for halogenated anesthetics

• Maria C. Guimarães,
• Mariene H. Duarte,
• Josué M. Silla and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2016, 12, 760–768, doi:10.3762/bjoc.12.76

• bioconformation is ruled by enzyme induced-fit; consequently, optimized and bioactive geometries are probably different to each other and, to obtain insight on the action mechanism of a drug and substituent effects, MD´s should not be generated over geometries optimized in a receptor-free environment. Efforts

My maize and blue brick road to physical organic chemistry in materials

• Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

• applying what I learned in class (e.g., substituent effects) to this unknown research question. I was driven by the desire to collect new data, and provide new information about the reactivity of these compounds [1][2]. Rob was a great mentor and role model; he had high expectations for himself and worked

• by our surprising substituent effects on the Diels–Alder regioselectivity in our monomer synthesis. Together we designed a collaborative project to further evaluate these effects. These studies led us to conclude that the π system is relatively unimportant and that substituent effects can instead be

Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

• Takamichi Wakamatsu,
• Kazunori Nagao,
• Hirohisa Ohmiya and
• Masaya Sawamura

Beilstein J. Org. Chem. 2015, 11, 2444–2450, doi:10.3762/bjoc.11.265

• protonolysis to form either syn-4 or anti-4 depending on the substituent effects of R1 and R2, while the isomerized alkenylcopper(I) D' should preferentially yield anti-4. The reduction of syn selectivity in the reaction with PPh3, PCy3 and DPPE may also be due to this isomerization (Table 1, entries 2–4

Chiroptical properties of 1,3-diphenylallene-anchored tetrathiafulvalene and its polymer synthesis

• Masashi Hasegawa,
• Junta Endo,
• Seiya Iwata,
• Toshiaki Shimasaki and
• Yasuhiro Mazaki

Beilstein J. Org. Chem. 2015, 11, 972–979, doi:10.3762/bjoc.11.109

• . These results suggest that the TTF units in both compounds are oxidized independently to form TTF/TTF•+ and, subsequently, TTF•+/TTF2+. A small positive shift of E11/2 in PTDPA is presumably due to the substituent effects of the two phenylene groups in the TTF unit. To investigate the electronic

Microsolvation and sp²-stereoinversion of monomeric α-(2,6-di-tert-butylphenyl)vinyllithium as measured by NMR

• Rudolf Knorr,
• Monika Knittl and
• Eva C. Rossmann

Beilstein J. Org. Chem. 2014, 10, 2521–2530, doi:10.3762/bjoc.10.263

• groups have been attributed [17][18] to σ-inductive substituent effects: More positive 2JH,H values should be caused by increasing σ-electron donation through the molecular σ-orbital framework within the double-bond plane [17]. In this spirit, the 2JH,H values of our model system 4 indicate that the sp2

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

• rearrangement; photoremovable protecting groups; Introduction Phosphates have long held an important formative position in the development of organic photochemistry beginning with the seminal report by Havinga [1] of the unusual substituent effects in the photosolvolysis of aryl phosphates that showed

New sesquiterpene hydroquinones from the Caribbean sponge Aka coralliphagum

• Qun Göthel and
• Matthias Köck

Beilstein J. Org. Chem. 2014, 10, 613–621, doi:10.3762/bjoc.10.52

• the acyclic to the bicyclic sesquiterpenoid moiety are drawn in red. The isomerizing double bond is drawn in blue. NMR data of compounds 1–5 (δC 150 MHz, δH 600 MHz in DMSO-d6).a 13C substituent effects Δδ in monosubstituted benzenes relative to the benzene carbon at 128.5 ppm [9]. Results of the

Additive-assisted regioselective 1,3-dipolar cycloaddition of azomethine ylides with benzylideneacetone

• Chuqin Peng,
• Jiwei Ren,
• Jun-An Xiao,
• Honggang Zhang,
• Hua Yang and
• Yiming Luo

Beilstein J. Org. Chem. 2014, 10, 352–360, doi:10.3762/bjoc.10.33

• 4-nitrobenzoic acid, respectively. The substituent effects on the regioselectivity were also investigated. Keywords: 1,3-dipolar cycloaddition; azomethine ylide; regioselectivity; spirooxindole; Introduction Spirooxindoles are important synthetic targets due to their significant biological

Garner’s aldehyde as a versatile intermediate in the synthesis of enantiopure natural products

• Mikko Passiniemi and
• Ari M.P. Koskinen

Beilstein J. Org. Chem. 2013, 9, 2641–2659, doi:10.3762/bjoc.9.300

• transition state model explains this selectivity [55]. The nucleophile attacks not only from the least hindered side (substituent effects), but also from the side where the low-lying σ*C–N orbital is aligned parallel with the π- and π*-orbital of the carbonyl group, allowing delocalization of electron

Elucidation of the regio- and chemoselectivity of enzymatic allylic oxidations with Pleurotus sapidus – conversion of selected spirocyclic terpenoids and computational analysis

• Verena Weidmann,
• Mathias Schaffrath,
• Holger Zorn,
• Julia Rehbein and
• Wolfgang Maison

Beilstein J. Org. Chem. 2013, 9, 2233–2241, doi:10.3762/bjoc.9.262

• as well as in the model system 11B-R3 helps to stabilize the radical further, mainly by hyperconjugation. In total, both substituent effects result in a rather low C–H bond-dissociation enthalpy of 79.5 kcal/mol at CBS-QB3 level of theory (74.9 kcal/mol B3LYP/6-31+G**, Table 2). Compared to the other

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• initial assessment of substituent effects on the rearrangement process is presented. Keywords: cycloaddition; diene; nitro; nitronate; rearrangement; Introduction We have previously reported examples of a general new [3,3]-sigmatropic rearrangement, the conversion of O-allyl nitronic esters (nitronates

ML212: A small-molecule probe for investigating fluconazole resistance mechanisms in Candida albicans

• Willmen Youngsaye,
• Cathy L. Hartland,
• Barbara J. Morgan,
• Amal Ting,
• Partha P. Nag,
• Benjamin Vincent,
• Carrie A. Mosher,
• Joshua A. Bittker,
• Sivaraman Dandapani,
• Michelle Palmer,
• Luke Whitesell,
• Susan Lindquist,
• Stuart L. Schreiber and
• Benito Munoz

Beilstein J. Org. Chem. 2013, 9, 1501–1507, doi:10.3762/bjoc.9.171

• bromoacetate, K2CO3, acetone, 60 °C; (d) alkylmagnesium bromide, Et2O, 0 °C; (e) Dess–Martin periodinane, CH2Cl2; (f) hydrazine hydrate, 175 °C. Activity of substituted indazole cores.a Investigation of 3-substituted indazoles.a Substituent effects associated with the 3-phenyl ring.a Supporting Information

Substituent effect on the energy barrier for σ-bond formation from π-single-bonded species, singlet 2,2-dialkoxycyclopentane-1,3-diyls

• Jianhuai Ye,
• Yoshihisa Fujiwara and
• Manabu Abe

Beilstein J. Org. Chem. 2013, 9, 925–933, doi:10.3762/bjoc.9.106

• diradicals. Thus, the aryl substituent was introduced at C(1), C(2), or/and C(3) positions of the diradicals DRd–g, and the substituent effects on the lifetime of the singlet diradicals were compared with the lifetime of a phenyl-group-substituted diradical DRc and the parent diradical DRa. The laser flash

Kinetics and mechanism of the anilinolysis of aryl phenyl isothiocyanophosphates in acetonitrile

• Hasi Rani Barai and
• Hai Whang Lee

Beilstein J. Org. Chem. 2013, 9, 615–620, doi:10.3762/bjoc.9.68

• ). The kinetic results of the present work are discussed based on the selectivity parameters and deuterium kinetic isotope effects (DKIEs). The aim of this work is to gain further information on the substituent effects, DKIEs and mechanism of the phosphoryl transfer reactions. Results and Discussion

• substituent effects of X on the reaction rates are not compatible with a typical nucleophilic substitution reaction. The Hammett and Brönsted plots with X are biphasic concave upwards with a break region between X = H and 4-Cl (break point of σX ≈ 0.13), giving unusual positive ρX and negative βX values with

• X = 4-Cl and 3-Cl. Positive ρX (and negative βX) values indicate that the nucleophilic N atom becomes more negative in the TS compared to in the ground state (GS). The substituent effects of Y on the reaction rates are consistent with a typical nucleophilic substitution reaction, and the rate

An efficient and practical entry to 2-amido-dienes and 3-amido-trienes from allenamides through stereoselective 1,3-hydrogen shifts

• Ryuji Hayashi,
• John B. Feltenberger,
• Andrew G. Lohse,
• Mary C. Walton and
• Richard P. Hsung

Beilstein J. Org. Chem. 2011, 7, 410–420, doi:10.3762/bjoc.7.53

• (135 °C), thereby implying an accelerated process of electrocyclization. This feature is consistently observed in related ring-closures of 1,3,5-hexatrienes with an electron-donating substituent at the C3 position of the triene [94][95][96][97][98][99] (for theoretical studies on substituent effects on

Effects of anion complexation on the photoreactivity of bisureido- and bisthioureido-substituted dibenzobarrelene derivatives

• Heiko Ihmels and
• Jia Luo

Beilstein J. Org. Chem. 2011, 7, 278–289, doi:10.3762/bjoc.7.37

• ) rearrangement [27][28] of dibenzobarrelene (dibenzobicyclo[2.2.2]octatriene) (1a) and its derivatives has been shown to be an appropriate model reaction for the assessment of substituent effects on the selectivity of organic photoreactions (Scheme 1) [29][30]. The photoreactivity of dibenzobarrelene derivatives

Heavy atom effects in the Paternò–Büchi reaction of pyrimidine derivatives with 4,4’-disubstituted benzophenones

• Feng-Feng Kong,
• Jian-Bo Wang and
• Qin-Hua Song

Beilstein J. Org. Chem. 2011, 7, 113–118, doi:10.3762/bjoc.7.16

• observations with those of systems of 1a (with electron-donating groups, EDGs), and 1b and 1f (also with EWGs). However, as a heavy atom effect, observations above can be rationalized based on the triplet mechanism of the Paternò–Büchi reaction. Results and Discussion Substituent effects To investigate

• substituent effects of benzophenones in the Paternò–Büchi reaction, photochemical reactions of DMT/DMU with 1a–f in acetonitrile-d3 were performed in Pyrex NMR tubes. The regioselectivity (the ratio of 2/3) and the yield were measured directly from the 1H NMR spectra of crude product mixtures and are listed

• benzophenones generate two series of regioisomeric oxetanes, 2 and 3, via 1,4-diradical intermediates, and reveal notable substituent effects on the regioselectivity and the photochemical efficiency. The reactions initiated by triplet benzophenones with EDGs give a higher proportion of 2 and a lower

β-Hydroxy carbocation intermediates in solvolyses of di- and tetra-hydronaphthalene substrates

• Jaya S. Kudavalli and
• Rory A. More O'Ferrall

Beilstein J. Org. Chem. 2010, 6, 1035–1042, doi:10.3762/bjoc.6.118

• -hydroxy-1,2-dihydronaphthalene. Rate constants for solvolysis of cis- and trans-1-trichloroacetoxy-2-methoxy-1,2-dihydronaphthalene (3) in acetonitrile-water mixtures at 25 °C. Solvolysis reactions: oxygen substituent effects on reactivitya. Supporting Information Supporting Information File 144