Solid-state synthesis of polyfunctionalized 2-pyridones and conjugated dienes.

Functionalized 2-pyridones are important biologically active compounds, DNA base analogues and synthetic intermediates. Herein, we report a simple, green, solid-state synthesis of differently substituted 2-pyridones. It starts from commercially available amines and activated alkynes, uses silica gel (15%Cs2CO3/SiO2) as the solid phase and a reaction vial as the only equipment. If necessary, heating is performed in a laboratory oven. Since most reactions are completed within a few hours, no additional energy consumption is required. The syntheses do not require solvents and other reagents and are easily monitored by standard analytical techniques. The atom economy is high, since all atoms of reactants are present in the products and EtOH is the only by-product. The syntheses produce polyfunctionalized conjugated dienes as the only intermediates, which are also important building blocks.

Theoretical investigation of tautomerism of 2- and 4-pyridones: origin, substituent and solvent effects.

Computational investigation at the BHandHLYP/6-311+G(d,p) level of theory of the gas-phase tautomerism of 2- and 4-pyridones confirmed the slight prevalence of lactim in the case of the former, but its dominance in the case of the latter, as shown previously. Examination of aromaticity by using HOMA, EDDB, NBOdel, NICS and AICD led to the conclusion that tautomerization of 4-pyridone results in greater aromaticity gain. It is also driven by the Pauli repulsion relief, which was revealed by the tautomerization energy decomposition analysis. By contrast, in the case of 2-pyridone, lactim is favoured by orbital and electrostatic interactions and disfavoured by the Pauli repulsion. Aromaticity gain in this case is smaller. The position of the tautomeric equilibrium can be modulated by substituent inductive effects (Cl and F), inductive and resonance effects (NH2 and NO2), hydrogen bonding (NO2), and medium polarity, the increase of which increases lactam population.

Solid-state silica gel-catalyzed synthesis of fluorescent polysubstituted 1,4- and 1,2-dihydropyridines.

We present the green, highly atom-economical, solid-state silica gel-catalyzed synthesis of polysubstituted 1,4- and 1,2-dihydropyridines (DHPs) from commercially available materials, amines and ethyl propiolate. The DHP skeleton was assembled by heating the reactants and silica gel in a closed vessel. Aliphatic amines provided 1,4-isomers as the main or only DHP products, but the reactions of aromatic amines yielded a mixture of 1,4- and 1,2-isomers. To the best of our knowledge, this is the first example of the formation of a 1,2-DHP structure by the reaction of an amine with propiolic ester. Addition of 1 mass percent of H2SO4 to silica gel shifted the product distribution to 1,4-DHP as the main or the only isomer obtained. Experimental and theoretical analyses led to the identification of two key intermediates en route to DHPs and the explanation of the observed regioisomeric ratios. 1,2-DHPs show blue-cyan fluorescence in MeOH with the quantum yield Φ = 0.10-0.22 relative to quinine sulfate Φ = 0.58 and 1,4-DHPs show blue-violet fluorescence with Φ = 0.09-0.81.

The role of melatonin in preventing amiodarone-induced rat liver damage.

Long-term exposure to amiodarone, an antiarrhythmic drug, can induce different organ damage, including liver. Cell damage included by amiodarone is a consequence of mitochondrial damage, reactive oxygen species production, and cell energy depletion leading to programmed cell death. In the present study, hepatoprotective potential of neurohormone melatonin (50 mg/kg/day) was evaluated in a chronic experimental model of liver damage induced by a 4-week application of amiodarone (70 mg/kg/day). The obtained results indicate that amiodarone induces an increase in xanthine oxidase activity, as well as the content of the lipid and protein oxidatively modified products and p53 levels. Microscopic analysis further corroborated the biochemical findings revealing hepatocyte degeneration, apoptosis, and occasional necrosis, with the activation of Kupffer cells. Coadministration of melatonin and amiodaron prevented an increase in certain damage associated parameters, due to its multiple targets. In conclusion, the application of melatonin together with amiodarone prevented an increase in tissue oxidative damage parameters and moderately prevented liver cell apoptosis, indicating that the damage of hepatocytes provoked by amiodarone supersedes the protective properties of melatonin in a given dose.

A Need for Improvement in the Definition of Resistant Arterial Hypertension.

With the medical and social importance of resistant arterial hypertension (HTN) in mind, we had three goals in this paper: to study the definitions of resistant HTN in the guidelines on the topic, to analyze them, and to suggest some improvements. We found (at least) eleven insufficiencies in the definition of resistant HTN: (1) different blood pressure (BP) values are used for diagnoses; (2) the number of BP measurements is not specified; (3) the time-frame for the definition is not obtained; (4) it fails to provide normal or target or controlled BP values; (5) secondary HTN is not currently defined as true resistant HTN, but as apparently treatment-resistant HTN; (6) the definition usually directly incorporates BP cut-offs for systolic BP (sBP) and diastolic BP (dBP) making the diagnosis temporary; (7) stress is not included in the exclusion strategy for resistant HTN; (8) there is potentially a need to introduce a category of recovered resistant HTN; (9) to what degree do healthy lifestyle measures have to be fulfilled to consider it as sufficient to change the diagnosis from "apparent treatment-resistant HTN" to the "resistant HTN"; (10) sBP values normal-for-the-age for 61 and 81 year old patients in some guidelines fulfill the criterion for resistant HTN; (11) it probably ought to read "In the absence of contraindications and compelling indications…" in the others. We believe that it is better to use the phrase "above the target BP" for the definition of (treatment) resistant HTN, because the whole story of resistant HTN is related to non-responders to antihypertensive treatment. Therefore, as we treat to target and not to normal values, it is appropriate to define resistant HTN as an insufficiency to reach the target BP values. Moreover, the definition of (treatment) resistant HTN should not be universal for every patient with HTN, but it should be age-related: (treatment) resistant HTN is elevated BP over the target/normal BP values. Using this modification, there will be no need to automatically change the definition of resistant HTN when we change the BP targets in the future.

A Discrepancy: Calcium Channel Blockers Are Effective for the Treatment of Hypertensive Left Ventricular Hypertrophy but Not as Effective for Prevention of Heart Failure.

Arterial hypertension (HTN) is important due to its high prevalence, morbidity, and mortality rates. Calcium channel blockers (CCBs) are the first-line antihypertensive drugs. HTN can lead to heart failure (HF) by causing hypertensive left ventricular hypertrophy (HTN LVH). CCBs are recommended for the treatment of HTN LVH. The aim of this study was to analyze the status of CCBs regarding (1) HTN LVH treatment and (2) capability to prevent HTN-induced HF in the guidelines. For this narrative review, the following databases were searched: Medline, Scopus, Science Direct, Springer, SAGE, Wiley, Oxford Journals, Cambridge, and Google Scholar. CCBs are effective antihypertensive drugs and a very good therapeutic option for HTN LVH as they can cause reverse LVH remodeling. Consequently, we may expect that CCBs would prevent HF. However, evidence suggests that CCBs confer less protection from HF than other first-line antihypertensive drugs. A negative inotropic action of nondihydropyridine CCBs may contribute to suboptimal protection against HF. This discrepancy is clinically relevant because CCBs are in one of the two recommended (single pill) combinations for the initial treatment of HTN. LVH is a strong risk factor for HF in HTN patients. When LVH arises, the risk of HF increases dramatically. CCBs are inferior to renin-angiotensin-aldosterone system blockers but still very effective in bringing about regression of HTN LVH; consequently, CCBs are expected to protect from HF. On the contrary, CCBs protect from HF less effectively than other first-line antihypertensive drugs. This discrepancy needs to be investigated further to improve clinical practice.

Synthesis of 2,3-Dihydro-4-pyridones and 4-Pyridones by the Cyclization Reaction of Ester-Tethered Enaminones.

2,3-Dihydro-4-pyridone skeleton is an important building block in organic synthesis because it features several reaction sites with nucleophilic or electrophilic properties. Herein, we disclose a method for its formation by intramolecular cyclization of ester-tethered enaminones, which can easily be synthesized from readily available materials, such as amines, activated alkynes, and activated alkenes. 2,3-Dihydro-4-pyridones have been isolated in 41-90% yields. We also demonstrate the transformation of these heterocycles into another important class of compounds, 4-pyridones, by utilizing 2,3,5,6-tetrachloro-p-benzoquinone (chloranil) as an oxidizing agent. The latter products were isolated in 65-94% yields.

Unsolved Problem: (Isolated) Systolic Hypertension with Diastolic Blood Pressure below the Safety Margin.

The problem of high systolic blood pressure (sBP) combined with low diastolic blood pressure (dBP) requires attention because sBP is directly and continuously related to the most important criterion, i.e., all-cause mortality, whereas dBP becomes inversely related to it after the age of 50-60 years. The European Society of Cardiology and European Society of -Hypertension (ESC/ESH) 2018 guidelines for hypertension (HTN) are helpful because they recommend a lower safety cut-off for in-treatment dBP. To prevent tissue hypoperfusion, these guidelines recommend that dBP should be ≥70 mm Hg during treatment. A patient with very elevated sBP (e.g., 220 mm Hg) and low dBP (e.g., 65 mm Hg) is difficult to treat if one strictly follows the guidelines. In this situation, the sBP is a clear indication for antihypertensive treatment, but the dBP is a relative contraindication (as it is <70 mm Hg, a safety margin recognized by the 2018 ESC/ESH guidelines). The dilemma about whether or not to treat isolated systolic hypertension (SH) patients with low dBP (<70 mm Hg) is evident from the fact that almost half (45%) remain untreated. This is a common occurrence and identifying this problem is the first step to solving it. We suggest that an adequate search and analysis should be performed, starting from the exploration of the prognosis of the isolated (I)SH subset of patients with a very low dBP (<70 mm Hg) at the beginning of already performed randomized clinical trials.

Does HAS-BLED risk score underestimate the risk of bleeding in patients with triple antithrombotic therapy?

stroke or other thromboembolic complications in patients with atrial fibrillation (AF). On the other hand, dual antiplatelet therapy (aspirin plus P2Y12 inhibitor) represents a cornerstone in the treatment of acute coronary syndrome. Atrial fibrillation is relatively common in patients with coronary artery disease and patients who undergo primary percutaneous coronary interventions (PCI) with stent implantation. They should be on triple antithrombotic therapy (TAT): preferably direct oral anticoagulants (DOAC) plus aspirin plus clopidogrel as it prevents ischemic as well as thromboembolic events. Before introducing OAT in patients with AF we must assess the risk of future bleeding episodes as OAT can lead to some life-threatening bleeding events. The most common risk score used for that purpose is HASBLED score. HAS-BLED score is valuable, proven tool in assessing future bleeding events in patients with AF. Nevertheless, it does not make the difference between dual and triple antithrombotic therapy which can be of great importance in preventing bleeding events.

Does aromaticity account for an enhanced thermodynamic stability? The case of monosubstituted azaborines and the stereoelectronic chameleonism of the NH2 group.

This work was initiated by the increasing interest in BN/CC isosterism and by the long-lasting interest in the concepts of aromaticity and substituent effects. We have theoretically examined the aromaticity and stability of monosubstituted BN isosters of benzene, the three isomeric azaborines. The results provide insight into the effect of substitution on two basic molecular properties, which are influenced, here, by the substituent effects and by the B/N relationship in the ring. The results, along with other examples in the literature, also warn chemists that the general belief that aromaticity accounts for enhanced thermodynamic stability is not always true. The stability of cyclic, conjugated compounds depends on several effects, and only one of them is aromaticity. In addition, our calculations predict a switching of electronic properties of the NH2 group from the usual p-electron donor to a π-electron acceptor when it is moved from the B/C atoms to the nitrogen atom in all isomers, or C6 in 1,3-azaborine. This is the result of the conformational change that places the NLP in the plane of the ring and the NH bonds in a favourable spatial position to act as acceptors of π-electron density.

The effect of two types of dibenzoannulation of pentalene on molecular energies and magnetically induced currents.

The effect of two types of dibenzo-fusion of pentalene in the singlet and triplet states on its molecular energies and magnetically induced ring currents was examined via density functional calculations. The isomerization energy decomposition analysis (IEDA) together with the calculated aromaticity indices (NICS(1)zz, HOMA and FLUπ), estimation of resonance energies (RE) and extra cyclic resonance energies (ECRE) via the NBO method, and the NICS-XY-scans revealed that the π-electronic system is the most important factor controlling the molecular energies. The [a,f] topology features greater delocalization, which results in two opposing effects: larger ECRE, but weaker π-bonding. The latter is mainly responsible for the higher energy of [a,f]-dibenzopentalene (DBP) (ΔEiso = 21.7 kcal mol-1), with the other effects being σ-orbital and electrostatic interactions. The reversal of energetic stability in the triplet states (ΔEiso = -10.8 kcal mol-1) mainly comes from the reduced Pauli repulsion in [a,f]-DBP, which stabilizes the unpaired spin density over the central trimethylenemethane subunit vs. the central pentalene subunit in [a,e]-DBP. Although the [a,e] topology only reduces the diatropic and paratropic currents of the elementary subunits, benzene and pentalene, the [a,f] topology also creates strong global paratropicity involving the benzene rings. Both DBP isomers are characterized by global and smaller semi-global and local diatropic currents in the triplet state.

Aromaticity of Diazaborines and Their Protonated Forms.

Substitution of a CH group in benzene with nitrogen has a little effect on its aromaticity (Wang et al., Org. Lett. 2010, 12, 4824). How does the same type of substitution affect aromatic character of the three isomeric azaborines? Does further protonation change aromaticity of diazaborines? This work is aimed at answering these questions. Such a knowledge should be of interest for further exploration and application of BN/CC isosterism. Aromaticity of diazaborines and their protonated forms is studied with the aid of four aromaticity indices, HOMA, NICS(0)πzz, PDI and ECRE. Generally, NICS(0)πzz and PDI point to similar aromaticity of diazaborines and their parent azaborines, while HOMA and ECRE indicate some changes. Thus, aromaticity of 1,2-azaborine slightly decreases/increases when CH meta/ortho,para to B is substituted with nitrogen. Aromaticity of the most aromatic 1,3-azaborine remains almost unchanged when CH meta to B and N is replaced with nitrogen, and becomes slightly weaker when any other CH group is substituted with nitrogen. Replacement of the CH ortho to N in 1,4-azaborine does not change much its cyclic delocalization, while replacement of the CH ortho to B leads to smaller cyclic delocalization. Protonated forms are either of similar or decreased aromaticity compared with neutral molecules.

Origin of Fluorine/Sulfur Gauche Effect of ß-Fluorinated Thiol, Sulfoxide, Sulfone, and Thionium Ion.

The well-known gauche preference in FCCX systems, where X is an electronegative element from Period 2, is widely exploited in synthetic, medicinal, and material chemistry. It is rationalized on the basis of σ(C-H) → σ*(C-F) hyperconjugation and electrostatic interactions. The recent report (Thiehoff, C.; et al. Chem. Sci. 2015, 6, 3565) showed that the fluorine gauche effect can extend to Period 3 elements, such as sulfur. The aim of the present work is to disclose factors governing conformational behavior of FCCS containing systems. We examine conformational preferences in seven classes of compounds by ab initio and DFT calculations and rationalize the results by quantitatively decomposing the anti/gauche isomerization energy into contributions from electrostatic, orbital, dispersion, and Pauli interactions, and energy spent on structural changes. The results show that the fluorine/sulfur gauche effect is primarily electrostatic (63-75%), while all orbital interactions contribute 22-41% to stabilizing interactions. Stereoelectronic effects, involved in orbital interactions, also play a role in gauche conformer stabilization.

QT Prolongation Preceding Ventricular Fibrillation After Amiodarone Administration: A Case Report.

Atrial fibrillation (AF) is the most common long-term arrhythmia in adults. Rhythm control in patients with AF involves efforts to restore and maintain sinus rhythm and is accomplished by medication, catheter ablation, or electrical cardioversion. Amiodarone represents one of the most commonly used antiarrhythmic medications. Prolonged use of amiodarone can lead to many side effects. One of the most severe side effects is drug-induced long QT syndrome (LQTS), which can cause malignant arrhythmias and sudden cardiac death. We presented a case of a 52-year-old male who was admitted to the Coronary Unit due to first diagnosed AF with a rapid ventricular response. After amiodarone infusion was administrated the patient lost consciousness and the monitor displayed torsades de pointes (TdP) ventricular tachycardia with rapid conversion to ventricular fibrillation (VF). Cardiac resuscitation with two direct current (DC) shocks was performed. The patient was stabilized, and restoration of sinus rhythm with significant QT prolongation on the ECG was noted. This is a rare case of short-term amiodarone administration causing LQTS, TdP, and VF. The findings or observations emphasize the significance of diligent ECG monitoring during amiodarone treatment.

Beta-blockers in Hypertensive Left Ventricular Hypertrophy and Atrial Fibrillation Prevention.

BACKGROUND: Hypertensive left ventricular hypertrophy (HTN LVH) is a key risk factor for atrial fibrillation (AF). OBJECTIVE: To evaluate the possible role of beta-blockers (BBs) in addition to a renin-angiotensinaldosterone system (RAAS) blocker in AF prevention in patients with HTN LVH. METHODS: We performed a PubMed, Elsevier, SAGE, Oxford, and Google Scholar search with the search items 'beta blocker hypertension left ventricular hypertrophy patient' from 2013-2023. In the end, a 'snowball search', based on the references of relevant papers as well as from papers that cited them was performed. RESULTS: HTN LVH is a risk factor for AF. In turn, AF substantially complicates HTN LVH and contributes to the genesis of heart failure (HF) with preserved ejection fraction (HFpEF). The prognosis of HFpEF is comparable with that of HF with reduced EF (HFrEF), and, regardless of the type, HF is associated with five-year mortality of 50-75%. The antiarrhythmic properties of BBs are wellrecognized, and BBs as a class of drugs are - in general - recommended to decrease the incidence of AF in HTN. CONCLUSION: BBs are recommended (as a class) for AF prevention in several contemporary guidelines for HTN. LVH regression in HTN - used as a single criterion for the choice of antihypertensive medication - does not capture this protective effect. Consequently, it is worth studying how meaningful this antiarrhythmic action (to prevent AF) of BBs is in patients with HTN LVH in addition to a RAAS blocker.

Magnetic anisotropy of the C-C single bond.

Anisotropic effects are broadly used in NMR spectroscopy for structure elucidation. With the development of computational methods it has become possible to quantify the effects and obtain further insight into their origin. Some classical interpretations have been questioned. Herein, we show that the classical "anisotropy cone" representing the anisotropic effect of the C-C single bond should be revised: deshielding at its side and shielding along its end are observed. Consequently, methyl, methylene, and methyne hydrogen atoms are not deshielded by C-C bonds as is conventionally explained in NMR spectroscopy textbooks. They are just less shielded than by the C-H bonds attached at the same carbon. In addition, this anisotropic effect is dependent on the environment and care should be taken when drawing conclusions based on it. For example, it differs for the staggered and eclipsed conformations of ethane in HCCH planes, as well as for cyclohexane. In fact, it is not the anisotropy of the C2-C3/C5-C6 bonds that determines the chemical shift difference of axial and equatorial protons of a rigid cyclohexane ring, but magnetic contributions from all bonds.

1H NMR chemical shifts of cyclopropane and cyclobutane: a theoretical study.

This study was undertaken in order to rationalize the peculiar (1)H NMR chemical shifts of cyclopropane (δ 0.22) and cyclobutane (δ 1.98) which are shifted upfield and downfield with respect to larger cycloalkanes (δ 1.44-1.54). This is conventionally accounted for by shielding contributions arising from an aromatic-like ring current in cyclopropane, involving six electrons in the three C-C bonds, and deshielding coming from the σ antiaromatic CC framework of cyclobutane. The shielding pattern arising from the cyclopropane and cyclobutane CC framework response to a perpendicular magnetic field was visualized as two-dimensional grid distribution of NICS values. Further insight into the origin of chemical shift values was obtained by the NCS-NBO analysis of proton shielding tensor. In the case of cyclopropane, the CC framework shielding pattern implies the existence of both delocalized and localized currents that have a dominant shielding effect on protons. The magnitude of C-H bonds shielding effect is significant, too. Unlike the conventional interpretation, the CC framework shields cyclobutane hydrogens, and its response to a perpendicular magnetic field is quite similar to responses of other planar σ CC frameworks.

Significance of Beta-Blocker in Patients with Hypertensive Left Ventricular Hypertrophy and Myocardial Ischemia.

BACKGROUND: Arterial Hypertension (HTN) is a key risk factor for left ventricular hypertrophy (LVH) and a cause of ischemic heart disease (IHD). The association between myocardial ischemia and HTN LVH is strong because myocardial ischemia can occur in HTN LVH even in the absence of significant stenoses of epicardial coronary arteries. OBJECTIVE: To analyze pathophysiological characteristics/co-morbidities precipitating myocardial ischemia in patients with HTN LVH and provide a rationale for recommending beta-blockers (BBs) to prevent/treat ischemia in LVH. METHODS: We searched PubMed, SCOPUS, PubMed, Elsevier, Springer Verlag, and Google Scholar for review articles and guidelines on hypertension from 01/01/2000 until 01/05/2022. The search was limited to publications written in English. RESULTS: HTN LVH worsens ischemia in coronary artery disease (CAD) patients. Even without obstructive CAD, several pathophysiological mechanisms in HTN LVH can lead to myocardial ischemia. In the same guidelines that recommend BBs for patients with HTN and CAD, we could not find a single recommendation for BBs in patients with HTN LVH but without proven CAD. There are several reasons for the proposal of using some BBs to control ischemia in patients with HTN and LVH (even in the absence of obstructive CAD). CONCLUSION: Some BBs ought to be considered to prevent/treat ischemia in patients with HTN LVH (even in the absence of obstructive CAD). Furthermore, LVH and ischemic events are important causes of ventricular tachycardia, ventricular fibrillation, and sudden cardiac death; these events are another reason for recommending certain BBs for HTN LVH.

Blood pressure cut-offs to diagnose impending hypertensive emergency depend on previous hypertension-mediated organ damage and comorbid conditions.

Background Hypertensive emergencies (HTN-E) are important due to a high risk of mortality. However, a sudden increase in blood pressure (BP) can damage target organs before the BP reaches cut-offs to diagnose HTN-E. We (i) analyse HTN guidelines for recommendations of treatment individualization, such as adjusting BP cut-offs for hypertensive urgency or impending HTN-E according to patient's susceptibility to complications (because of previous hypertension-mediated organ damage [HMOD], cardiovascular events and comorbid conditions), and (ii) provide a rationale for the inclusion of patient's susceptibility in protocols for treatment of acute HTN-E. Methods We searched PubMed, SCOPUS, Science Direct, Springer, Oxford Press, Wiley, SAGE and Google Scholar for the following terms: arterial hypertension, impending, emergency, target organ damage, hypertension-mediated organ damage, and comorbidity. Results The available guidelines do not recommend that when we estimate the probability of HTN-E in a patient with very high BP, we take into account not only the 'aggressive factor' (i.e. history of HTN, absolute BP values and rate of its increase), but also the 'vulnerability of the patient' due to previous major adverse cardio-vascular events, HMOD and comorbid conditions. Conclusion The risk does not depend only on the aggressiveness of the health threat but also on the strength of the host's defence. It is, therefore, surprising that one side of the natural interaction (i.e. susceptibility of a patient) is overlooked in almost all available guidelines on HTN.