Reply to Kawasaki et al. Comment on "Manole et al. Primary Pericardial Synovial Sarcoma: A Case Report and Literature Review. Diagnostics 2022, 12, 158".

Thank you for your comment; it adds value to the article and highlights the importance of molecular testing [...].

Orthopalladated imidazolones and thiazolones: synthesis, photophysical properties and photochemical reactivity.

The reaction of Pd(OAc)2 with (Z)-5-arylidene-4-(4H)-imidazolones (2a-e) and (Z)-4-arylidene-5(4H)-thiazolones (3a-e) in trifluoroacetic acid results in the corresponding orthopalladated dinuclear complexes (4a-e, imidazolones; 11a-d, thiazolones) with trifluoroacetate bridges through regioselective C-H activation at the ortho position of the 4-arylidene group. Compound 4e, which contains an imidazolone substituted at 2- and 4-positions of the arylidene ring with methoxide groups and exhibits strong push-pull charge transfer, is an excellent precursor for the synthesis of fluorescent complexes with green yellowish emission and remarkable quantum yields. Breaking the bridging system with pyridine yields the mononuclear complex 5e (ΦF = 5%), while metathesis of trifluoroacetate ligands with chloride leads to the dinuclear complex 6e, also a precursor of fluorescent complexes by breaking the chloride bridging system with pyridine (7e, ΦF = 7%), or by substitution of chloride ligands with pyridine (8e, ΦF = 15%) or acetylacetonate (9e, ΦF = 2%). In addition to notable photophysical properties, dinuclear complexes 4 and 11 also exhibit significant photochemical reactivity. Thus, irradiation of orthopalladates 4a-c and 11a-c in CH2Cl2 with blue light (465 nm) proceeds via [2 + 2] photocycloaddition of the CC double bonds of imidazolone and thiazolone ligands, yielding the corresponding cyclobutane-bridging diaminotruxillic derivatives 10a-c and 12a-c, respectively.

Metal Complexes Containing Homoleptic Diorganoselenium(II) Ligands: Synthesis, Characterization and Investigation of Optical Properties.

[(Z)-2'-{2-C6H5-(4H)-oxazol-5-one}CHC6H4]2Se (5, L1) and [(Z)-4'-{2-C6H5-(4H)-oxazol-5-one}CHC6H4]2Se (6, L2) were prepared, structurally characterized and used as ligands to obtain new metal complexes of types [MX(Ln)] [L1: M = Ag, X = OTf (7); M = Au, X = Cl (13); L2: M = Ag, X = OTf (8); M = Au, X = Cl (14)], [(MX)2(Ln)] [M = Ag, X = OTf, L1 (9); L2 (10)], [ZnCl2(Ln)] [L1 (15); L2 (16)] and [Ag(Ln)][PF6] [L1 (11); L2 (12)]. The silver complexes 7 and 8 were ionic species (1:1 electrolytes) in a MeCN solution, while in the solid state, the triflate fragments were bonded to the silver cations. Similarly, the 2:1 complexes 9 and 10 were found to behave as 1:2 electrolytes in a MeCN solution, but single-crystal X-ray diffraction demonstrated that compound 9 showed the formation of a dimer in the solid state: a tetranuclear [Ag(OTf)]4 built through bridging triflate ligands was coordinated by two bridging organoselenium ligands through the nitrogen from the oxazolone ring and the selenium atoms in a 1κN:2κSe fashion. Supramolecular architectures supported by intermolecular C-H∙∙∙π, C-H∙∙∙O, Cl∙∙∙H and F∙∙∙H interactions were observed in compounds 4, 5 and 9. The compounds exhibited similar photophysical properties, with a bathochromic shift in the UV-Vis spectra caused by the position of the oxazolone ring on the phenyl ring attached to the selenium atoms.

Novel 3D versus traditional transesophageal echocardiography techniques: Defining differences in the diagnosis of infective endocarditis.

BACKGROUND: Despite the availability of current antibiotic and surgical treatment options, infective endocarditis (IE) remains associated with a high mortality rate. Even though two-dimensional (2D) transesophageal echocardiography (TOE) is a major criteria in the diagnosis of IE, it is constrained by the single-plane orientation. Since three-dimensional (3D) TOE provides a comprehensive understanding of the cardiac architecture by allowing for a realistic visualization of the underlying structures in 3D space, it has attracted considerable interest in recent years. AIM: The purpose of this narrative review is to discuss the advantages and pitfalls of 3D TOE in patients with IE, as well as to address emerging photo-realistic 3D techniques that have the potential to enhance the visualization of cardiac structures in this setting. RESULTS: According to recent research, 3D TOE acquisitions outperform 2D acquisitions in terms of vegetation identification accuracy and embolism risk assessment. By reporting a variety of findings that are missed with 2D TOE, but which are validated by surgical examination, 3D TOE further improves the ability to identify endocarditis complications on both native and prosthetic valves. In addition to conventional 3D TOE, future developments in 3D technology led to the development of transillumination and tissue-transparency rendering, which may improve anatomical understanding and depth perception. Due to the use of both conventional and novel 3D techniques, there are more patients who require surgical intervention, indicating that 3D TOE may have a clinical relevance on the surgical management. CONCLUSION: 3D TOE might fill the gaps left by 2D TOE in the diagnosis of IE.

Planar Chiral p,p'-Terphenyl-Based Cyclophanes with Remarkable Enantiomer Stability: Synthesis, Theoretical Investigations, and Complexation Studies.

Design of conformationally stable compounds with planar chirality is a topic of great interest mainly because of their potential applications as enantioselective ligands or other functional materials. Herein, we present the design and synthesis of novel planar chiral cyclophanes, obtained by ortho, ortho″ anchoring of the p,p'-terphenyl unit, with bridges of different lengths and rigidities, along with their nuclear magnetic resonance, mass spectrometry, and X-ray characterizations. We investigated the influence of the structural particularities of the bridges over the stability of the enantiomers, by means of nuclear magnetic resonance and chiral high-performance liquid chromatography as well as by density functional theory calculations. We also demonstrated the ability of one of the cyclophanes to preferentially bind arginine with Ka > 110 M-1 (ΔG > -11 kJ mol-1) in acetonitrile solutions containig 10 % water, in the presence of other amino acids.

Prognostic Value of Myocardial Function Imaging Markers in Elderly Patients Undergoing Transcatheter Aortic Valve Replacement.

Background: Transcatheter aortic valve replacement (TAVR) became the leading therapeutic strategy for aortic valve replacement in older patients with severe symptomatic aortic stenosis. Echocardiographic parameters that mark the left ventricle and right ventricle reverse remodeling after the TAVR are not well established. The aim of the current study is to describe the dynamics of both left ventricle (LV) and right ventricle (RV) strain derived from speckle tracking echocardiography in elderly patients at 3-months after the TAVR procedure. Methods: We enrolled 52 consecutive patients (77 ± 4.9 years old, median STS score of 3.1) who underwent transfemoral TAVR at our tertiary care center. All patients were evaluated at baseline and 3 months following TAVR. Results: The LV global longitudinal strain (GLS) 3-month following TAVR was significantly improved compared with baseline values (-16 ±4.2% vs -16 ±4.2%; p < 0.001) but no significant changes in the RV GLS 3 and 6 segments model following TAVR were registered. The LV ejection fraction was significantly improved 3-months after the TAVR procedure. LV-GLS at baseline demonstrated a strong positive correlation with LV-GLS at 3 months (r = 0.69) and a moderate correlation with RV strain parameters (r = 0.38 and r = 0.56), but also a negative correlation with LVEF at follow-up (r=-0.61). Interestingly, in contrast to LVEF, none of the strain parameters correlated with age. NT-proBNP values were correlated with both LV-GLS (r = 0.37) and LVEF (r=-0.5) at baseline. However, at follow-up, baseline NT-proBNP values remained correlated only to LV-GLS at 3-months (r = 0.24), but the correlation was weak.

BMP-induced non-canonical signaling is upregulated during autophagy-mediated regeneration in inflamed mesothelial cells.

Previously, we showed that after Freund's adjuvant-induced peritonitis, rat mesothelial cells regain their epithelial phenotype through mesenchymal-epithelial transition (MET) accompanied by autophagy. Since bone morphogenetic proteins (BMPs) are well-known MET-inducers, we were interested in the potential expression of BMPs and BMP-induced pathways. Although mesothelial cells expressed lower amounts of BMP7, its level in the peritoneal cavity and mesothelial synthesis of BMP4 were significantly increased during inflammation. BMPR1A and BMPR2 were also significantly expressed. Expression of transforming growth factor beta-activated kinase (TAK1) and c-Jun NH2-terminal kinases (JNK1-JNK2) were more intense than that of phosphorylated Mothers Against Decapentaplegic homolog 1/5 (p-SMAD1/5), confirming that the non-canonical pathway of BMPs prevailed in our model. JNK signaling through B-cell lymphoma-2 (Bcl-2) can contribute to Beclin-1 activation. We demonstrated that TAK1-JNK-Bcl-2 signaling was upregulated simultaneously with the autophagy-mediated regeneration. A further goal of our study was to prove the regenerative role of autophagy after inflammation. We used a specific inhibitor, bafilomycin A1 (BafA1), and found that BafA1 treatment decreased the expression of microtubule-associated protein 1A/1B-light chain 3 (LC3B) and resulted in morphological signs of cell death in inflamed mesothelial cells indicating that if autophagy is arrested, regeneration turns into cell death and consequently, mesothelial cells die.

Diagnosis of Left-Sided Mechanical Prosthetic Valve Thrombosis: A Pictorial Review.

Although transcatheter valve therapy is rapidly evolving, surgical valve replacement is still required in many patients with severe left-side valve stenosis or regurgitation, the mechanical bi-leaflet heart valve being the standard prosthesis type in younger patients. Moreover, the prevalence of valvular heart disease is steadily increasing, especially in industrialized countries, and the problem of lifelong efficient anticoagulation of these patients remains fundamental, especially in the context where vitamin K antagonists continue to be the current standard of anticoagulation despite a level of oscillating anticoagulation. In this setting, avoiding prosthetic valve thrombosis after surgery is the number one objective for both the patient and the responsible physicians. Although rare, this complication is life threatening, with the sudden onset of acute cardiac failure such as acute pulmonary edema, cardiogenic shock, or sudden cardiac death and inadequate anticoagulation remaining the leading cause of prosthesis thrombosis, along with other risk factors. The availability of multimodal imaging techniques enables and encompasses to a full extent the diagnosis of mechanical valve thrombosis. The gold-standard diagnostic methods are transthoracic and transesophageal echocardiography. Moreover, 3D ultrasound has undoubted value in giving a more accurate description of the thrombus's extension. When transthoracic and transesophageal echocardiography are uncertain, the multidetector computer tomography examination is an important complementary imaging method. Fluoroscopy is also an excellent tool for evaluating the mobility of prosthetic discs. Each method complements the other to differentiate an acute mechanical valve thrombosis from other prosthetic valve pathologies such as pannus formation or infective endocarditis and aids the physician in accurately establishing the treatment method (surgical or pharmaceutical) and its optimal timing. The aim of this pictorial review was to discuss from an imagistic perspective the mechanical prosthetic aortic and mitral valve thrombosis and to provide an overview of the essential role of non-invasive exploration in the treatment of this severe complication.

Correlation between Coronary Artery Disease with Other Arterial Systems: Similar, Albeit Separate, Underlying Pathophysiologic Mechanisms.

Atherosclerosis is a multifactorial systemic disease that affects the entire arterial tree, although some areas are more prone to lipid deposits than others. Moreover, the histopathological composition of the plaques differs, and the clinical manifestations are also different, depending on the location and structure of the atherosclerotic plaque. Some arterial systems are correlated with each other more than in that they simply share a common atherosclerotic risk. The aim of this perspective review is to discuss this heterogeneity of atherosclerotic impairment in different arterial districts and to investigate the current evidence that resulted from studies of the topographical interrelations of atherosclerosis.

The Role of Multimodality Imaging in the Diagnosis and Follow-Up of Malignant Primary Cardiac Tumors: Myxofibrosarcoma-A Case Report and Literature Review.

Cardiac tumors are a very rare but heterogenous group of diseases that may reveal themselves through a variety of nonspecific cardiac symptoms that may pose a challenge to the diagnostic process. Myxofibrosarcoma is a particularly rare type of cardiac tumor that carries a poor prognosis, thus making accurate and timely diagnosis essential. A 61-year-old woman presented with fatigue and shortness of breath during mild exercise, symptoms that have progressively worsened during the previous year. Multimodality imaging consisting of transthoracic and transesophageal echocardiography (TTE and TEE), cardiac magnetic resonance (CMR), cardiac computer tomography (CCT), and fluorodeoxyglucose positron emission computer tomography (18F-FDG PET-CT) was used for the diagnosis and postoperative follow-up of a myxofibrosarcoma.

The Degree of Stent Apposition Measured by Stent Enhancement at the Level of the Side Branch as a Novel Predictor of Procedural Success in Left Main PCI.

BACKGROUND: Stent enhancement techniques allow adequate visualization of stent deformation or incomplete stent expansion at the ostium of the side branch. Measuring the stent enhancement side branch length (SESBL) could reflect procedural success in terms of optimal stent expansion and apposition with better long-term outcomes. A longer SESBL may reflect a better stent apposition at the polygon of confluence and at the side branch (SB) ostium. METHODS: We evaluated 162 patients receiving the left main (LM) provisional one-stent technique and measured the SESBL, dividing them into two groups: SESBL≤ 2.0 mm and SESBL > 2.0 mm. RESULTS: The mean SESBL was 2.0 ± 1.2 mm. More than half of the bifurcations had both main and side branch lesions (Medina 1-1-1) (84 patients, 51.9%) and the length of the SB disease was 5.2 ±1.8 mm. Kissing balloon inflation (KBI) was performed in 49 patients (30.2%). During follow-up (12 months), there was a significantly higher rate of cardiac death in the SESBL ≤ 2.0 mm group (p = 0.02) but no significant difference in all major adverse cardiovascular events (MACEs) (p = 0.7). KBI did not influence the outcomes (p = 0.3). CONCLUSION: Suboptimal SESBL is positively correlated with worse outcomes and SB compromise. This novel sign could aid the LM operator to assess the level of stent expansion at the ostium of the SB in the absence of intracoronary imaging.

Synthesis of Bis(amino acids) Containing the Styryl-cyclobutane Core by Photosensitized [2+2]-Cross-cycloaddition of Allylidene-5(4H)-oxazolones.

The irradiation of 2-aryl-4-(E-3'-aryl-allylidene)-5(4H)-oxazolones 1 with blue light (456 nm) in the presence of [Ru(bpy)3](BF4)2 (bpy = 2,2'-bipyridine, 5% mol) gives the unstable cyclobutane-bis(oxazolones) 2 by [2+2]-photocycloaddition of two oxazolones 1. Each oxazolone contributes to the formation of 2 with a different C=C bond, one of them reacting through the exocyclic C=C bond, while the other does so through the styryl group. Treatment of unstable cyclobutanes 2 with NaOMe/MeOH produces the oxazolone ring opening reaction, affording stable styryl-cyclobutane bis(amino acids) 3. The reaction starts with formation of the T1 excited state of the photosensitizer 3[Ru*(bpy)3]2+, which reacts with S0 of oxazolones 1 through energy transfer to give the oxazolone T1 state 3(oxa*)-1, which is the reactive species and was characterized by transient absorption spectroscopy. Measurement of the half-life of 3(oxa*)-1 for 1a, 1b and 1d shows large values for 1a and 1b (10-12 µs), while that of 1d is shorter (726 ns). Density functional theory (DFT) modeling displays strong structural differences in the T1 states of the three oxazolones. Moreover, study of the spin density of T1 state 3(oxa*)-1 provides clues to understanding the different reactivity of 4-allylidene-oxazolones described here with respect to the previously reported 4-arylidene-oxazolones.

Clinical Characteristics and Outcomes following Percutaneous Coronary Intervention in Unprotected Left Main Disease: A Single-Center Study.

Background: Hemodynamically significant unprotected left main (LM) coronary artery disease is a high-risk clinical condition because of the large area of myocardium at risk, and it requires prompt revascularization. Percutaneous coronary intervention (PCI) is an appropriate alternative to coronary artery bypass grafting (CABG) for revascularization of unprotected LM disease in patients with low-to-intermediate anatomic complexity or when the patient refuses CABG after adequate counseling by the heart team. Methods: We retrospectively evaluated 201 patients receiving left main (LM) provisional one-stent or two-stent procedures, and we assessed the clinical characteristics and outcomes of patients undergoing unprotected LM PCI. Results: The mean age was 66.5 ± 9.9 years, and 72% were male. The majority of the subjects presented several cardiovascular risk factors, among which arterial hypertension (179 patients, 89.5%) and dyslipidemia (173 patients, 86.5%) were the most frequent. Out of all patients, 162 (81.8%) underwent revascularization by using the one-stent technique, while the two-stent technique was used in 36 patients (18.2%). The median value of fractional flow reserve (FFR) of the side branch was 0.9 [0.85-0.95], and 135 patients (67.1%) showed a value of FFR > 0.8. One hundred nine patients (54.2%) had a stent enhancement side branch length (SESBL) > 2, with median values of 2.5 mm2 [2.1-3]. Regarding angiographic parameters, the LM area as assessed by intravascular ultrasound (IVUS) or optical coherence tomography (OCT) and the grade of stenosis as assessed by quantitative coronary angiography (QCA) were similar between groups. However, patients who required revascularization by using the two-stent technique presented more frequently with intermediate rather than low SYNTAX scores (69.4% vs. 28.4%, p < 0.0001). Also, the same group required kissing balloon inflation (KBI) more frequently (69.4% vs. 30%, p < 0.001). There were no differences regarding the success of revascularization between the use of the one-stent or two-stent technique. FFR was able to predict a SESBL > 2 mm. The cut-off value for FFR to afford the highest degree of sensitivity (74.5%) and specificity (47%) for a SESBL > 2 was >0.86, indicating a moderate accuracy (AUC = 0.61, 95% CI 0.525-0.690, p = 0.036). Conclusions: Unprotected left main PCI is a safe and effective revascularization option amongst a complex and morbid population. There were no differences regarding the success of revascularization between the use of the one-stent or two-stent technique, and there was no significant impact of KBI on side branch FFR measurements but lower side branch FFR values were correlated with angiographic side branch compromise.

Surgical Atrial Septal Patch Endocarditis in a Patient with a Complete Corrected Atrioventricular Canal Defect: A Case Report and Review of the Literature.

Infective endocarditis (IE) is common in patients with corrected congenital heart disease (CHD) with a residual lesion, but is rarely found on surgical patches used to close atrial septal defects (ASDs). This is also reflected in the current guidelines that do not recommend antibiotic therapy for patients with a repaired ASD with no residual shunt six months after closure (percutaneous or surgical). However, the situation could be different in the case of mitral valve endocarditis, which causes leaflet disruption with severe mitral insufficiency and could seed the surgical patch. We present herein a 40-year-old male patient with a past medical history of a complete surgically corrected atrioventricular canal defect performed in childhood who presented with fever, dyspnea and severe abdominal pain. Transthoracic and transesophageal echocardiography (TTE and TEE) revealed vegetation at the level of the mitral valve and the interatrial septum. The CT scan confirmed ASD patch endocarditis and multiple septic emboli, guiding the therapeutic management. An accurate evaluation of cardiac structures should be mandatory when a systemic infection is detected in CHD patients, even if the defects were surgically corrected, because the detection and eradication of such infectious foci as well as a surgical reintervention are particularly difficult to achieve in this subpopulation.

The Role of Echocardiography in the Diagnosis of Cardiac Involvement in a Rare Systemic Condition: The Carcinoid Heart Disease: A Case Report and Review of Literature.

Carcinoid heart disease is a rare presentation of the carcinoid syndrome, which is caused by excessive tumoral hormone production and the abundant release of vasoactive substances with systemic expressions. A 62-year-old woman presented with flushing, diarrhea, weight loss, and right-sided heart failure symptoms. Specific carcinoid heart disease features were identified using transthoracic and transesophageal echocardiography at the tricuspid and pulmonic valves. Biomarkers, 99mTc-Tektrotyd scintigraphy, SPECT-CT, and a biopsy later confirmed the diagnosis, and the patient began treatment for the underlying condition.

A Rare Case of Successfully Treated Double Valve Infective Endocarditis Caused by Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a rare yet particularly aggressive infective endocarditis pathogen. We describe a case of successfully managed double-valve P. aeruginosa infective endocarditis, in which the presumed source of bacteremia was a long-term tunneled central venous catheter used for hemodialysis.

Percutaneous Coronary Intervention versus Coronary Artery Bypass Grafting for Non-Protected Left Main Coronary Artery Disease: 1-Year Outcomes in a High Volume Single Center Study.

INTRODUCTION: There is clear evidence of a significant reduction in all major cardiovascular adverse events (MACE) by coronary artery bypass grafting (CABG) in left main coronary artery stenosis (LMCS), but revascularization by percutaneous coronary artery intervention (PCI) shows an increasingly important role as an alternative to CABG. Several recent trials aiming to test the difference in mortality between the two types of revascularization found conflicting data. The aim of this study is to determine whether PCI is non-inferior to CABG with respect to the occurrence of MACE at 1 year in patients with significant LMCS. MATERIAL AND METHODS: We prospectively enrolled 296 patients with chronic or acute coronary syndromes and significant LM stenosis. The angiography that recommended the revascularization procedure was used for the calculation of the Syntax II score, in order to classify the patients as low-, intermediate- or high-risk. Low- and high-risk patients were revascularized with either PCI or CABG, according to current guidelines, and were included in the subgroup S1. The second subgroup (S0) included intermediate-risk patients (Syntax II score 23-32), in whom the type of revascularization was chosen depending on the decision of the heart team or the patient preference. Patients were monitored according to the chosen mode of revascularization-PCI or CABG. LM revascularization was performed in all the patients. Clinical endpoints included cardiac death, myocardial infarction, need for revascularization and stroke. Patients were evaluated at 1 year after revascularization. Event rates were estimated using the Kaplan-Meier analysis in time to the first event. RESULTS: At 1-year follow-up, a primary endpoint occurred in 35/95 patients in the CABG group and 37/201 in the PCI group. There were no significant differences between the 2 treatment strategies in the 1-year components of the end-point. However, a tendency to higher occurrence of cardiac death (HR = 1.48 CI (0.55-3.9), p = 0.43), necessity of repeat revascularization (HR = 1.7, CI (0.81-3.6), p = 0.16) and stroke (HR = 1.52, CI (1.15-2.93), p = 0.58) were present after CABG. Contrariwise, although without statistical significance, MI was more frequent after PCI (HR = 2, CI (0.78-5.2), p = 0.14). The Kaplan-Meier estimates in subgroups demonstrated the same tendency to higher rates for cardiac death, repeat revascularization and stroke after CABG, and higher rates of MI after PCI. Although without statistical significance, patients with an intermediate-risk showed a slightly lower risk of MACE after PCI than CABG. With the exception of dyslipidemia and gender, other cardiovascular risk factors were in favor of CABG (CKD, obesity). CONCLUSION: In patients with LMCS, PCI with drug-eluting stents was non-inferior to CABG with respect to the composite of cardiac death, myocardial infarction, repeat revascularization and stroke at 1 year, even in patients with intermediate Syntax II risk score.

Diagnostic Challenges in Rare Causes of Arrhythmogenic Cardiomyopathy-The Role of Cardiac MRI.

Arrhythmogenic right ventricular dysplasia (ARVD) is a rare genetic condition of the myocardium, with a significantly high risk of sudden death. Recent genetic research and improved understanding of the pathophysiology tend to change the ARVD definition towards a larger spectrum of myocardial involvement, which includes, in various proportions, both the right (RV) and left ventricle (LV), currently referred to as ACM (arrhythmogenic cardiomyopathy). Its pathological substrate is defined by the replacement of the ventricular myocardium with fibrous adipose tissue that further leads to inadequate electrical impulses and translates into varies degrees of malignant ventricular arrythmias and dyskinetic myocardium movements. Particularly, the cardio-cutaneous syndromes of Carvajal/Naxos represent rare causes of ACM that might be suspected from early childhood. The diagnostic is sometimes challenging, even with well-established rTFC or Padua criteria, especially for pediatric patients or ACM with LV involvement. Cardiac MRI gain more and more importance in ACM diagnostic especially in non-classical forms. Furthermore, MRI is useful in highlighting myocardial fibrosis, fatty replacement or wall movement with high accuracy, thus guiding not only the depiction, but also the patient's stratification and management.

Stereoselective, Ruthenium-Photocatalyzed Synthesis of 1,2-Diaminotruxinic Bis-amino Acids from 4-Arylidene-5(4H)-oxazolones.

The irradiation of (Z)-2-phenyl-4-aryliden-5(4H)-oxazolones 1 in deoxygenated CH2Cl2 at 25 °C with blue light (465 nm) in the presence of [Ru(bpy)3](BF4)2 (5% mole ratio) as a triplet photocatalyst promotes the [2+2] photocycloaddition of the C═C bonds of the 4-arylidene moiety, thus allowing the completely regio- and stereoselective formation of cyclobutane-bis(oxazolone)s 2 as single stereoisomers. Cyclobutanes 2 have been unambiguously characterized as the µ-isomers and contain two E-oxazolones coupled in an anti-head-to-head form. The use of continuous-flow techniques in microreactors allows the synthesis of cyclobutanes 2 in only 60 min, compared with the 24-48 h required in batch mode. Ring opening of the oxazolone heterocycle in 2 with a base affords the corresponding 1,2-diaminotruxinic bis-amino esters 3, which are also obtained selectively as µ-isomers. The ruthenium complex behaves as a triplet photocatalyst, generating the reactive excited state of the oxazolone via an energy-transfer process. This reactive excited state has been characterized as a triplet diradical 3(E/Z)-1* by laser flash photolysis (transient absorption spectroscopy). This technique also shows that this excited state is the same when starting from either (Z)- or (E)-oxazolones. Density functional theory calculations show that the first step of the [2+2] cycloaddition between 3(E/Z)-1* and (Z)-1 is formation of the C(H)-C(H) bond and that (Z) to (E) isomerization takes place at the 1,4-diradical thus formed.