Chiral bisphosphine Ph-BPE ligand: a rising star in asymmetric synthesis.

Chiral 1,2-bis(2,5-diphenylphospholano)ethane (Ph-BPE) is a class of optimal organic bisphosphine ligands with C2-symmetry. Ph-BPE with its excellent catalytic performance in asymmetric synthesis has attracted much attention of chemists with increasing popularity and is growing into one of the most commonly used organophosphorus ligands, especially in asymmetric catalysis. Over two hundred examples have been reported since 2012. This review presents how Ph-BPE is utilized in asymmetric synthesis and how powerful it is as a chiral ligand or even a catalyst in a wide range of reactions including applications in the total synthesis of bioactive molecules.

Nonplanar Aromaticity of Dinuclear Rare-Earth Metallacycles.

While the concept of metalla-aromaticity has well been extended to transition organometallic compounds in diverse geometries, aromatic rare-earth organometallic complexes are rare due to the special (n - 1)d0 configuration and high-lying (n - 1)d orbitals of rare-earth centers. In particular, nonplanar cases of rare-earth complexes have not been reported so far. Here, we disclose the nonplanar aromaticity of dinuclear scandium and samarium metallacycles characterized by various aromaticity indices (nucleus-independent chemical shift, isochemical shielding surface, anisotropy of induced current density, and isomerization stabilization energy). Bonding analyses (Kohn-Sham molecular orbital, adaptive natural density partitioning, multicenter bond indices, and principal interacting orbital) reveal that three delocalized π orbitals, predominantly contributed by the 2-butene tetraanion ligand, result in the formation of six-electron conjugated systems. Guided by these findings, we predicted that the lutetium and gadolinium analogues of dinuclear rare-earth metallacycles should be aromatic, which have been verified by the successful synthesis of real molecules. This work extends the concept of nonplanar aromaticity to the field of rare-earth metallacycles and illuminates the path for designing and synthesizing various rare-earth metalla-aromatics.

Direct Synthesis of Phosphoryltriacetates from White Phosphorus via Visible Light Catalysis.

Organophosphorus compounds (OPCs) are widely used in many fields. However, traditional synthetic routes in the industry usually involve multistep and hazardous procedures. Therefore, it's of great significance to construct such compounds in an environmentally-friendly and facile way. Herein, a photoredox catalytic method has been developed to construct novel phosphoryltriacetates. Using fac-Ir(ppy)3 (ppy=2-phenylpyridine) as the photocatalyst and blue LEDs (456 nm) as the light source, white phosphorus can react with α-bromo esters smoothly to generate phosphoryltriacetates in moderate to good yields. This one-step approach features mild reaction conditions and simple operational process without chlorination.

Cascade C-H Activation and Two C-C Bond Forming in Reaction of Azalutetacyclopentadiene with 2-Methylbenzonitriles.

Azametallacyclopentadienes are an important class of metallacycles as the key intermediates in metal-promoted or catalyzed carbon-carbon coupling reaction of nitriles and alkynes. Rare-earth azametallacyclopentadienes have shown unique reactivity toward benzonitriles. The reaction chemistry of azalutetacyclopentadienes toward 2-methylbenzonitriles has been investigated in this work, showing different reactivity. Experimental and computational studies reveal that the reaction selectively initiates with the remote activation of the benzylic C-H bond by the Lu-N bond, followed by the intramolecular nucleophilic attack from the deprotonated benzylic carbon to form a C-C bond. Subsequently, the high ring strain promoted the generation of the uncoordinated carbanion dissociated from the lutetium center, which then undergoes intramolecular nucleophilic attack toward C≡N triple bond to give the final product containing fused 7-5-6-membered azalutetacycle. This work not only achieves highly selective three-step cascade transformation to form a unique class of rare-earth metallacycle, but also reveals a novel reaction pattern of unsaturated substrates with C-H bonds that can be activated.

Structure, Properties, Preparation, and Application of Layered Titanates.

As a typical cation-exchangeable layered compound, layered titanate has a unique open layered structure. Its excellent physical and chemical properties allow its wide use in the energy, environmental protection, electronics, biology, and other fields. This paper reviews the recent progress in the research on the structure, synthesis, properties, and application of layered titanates. Various reactivities, as well as the advantages and disadvantages, of different synthetic methods are discussed. The reaction mechanism and influencing factors of the ion exchange reaction, intercalation reaction, and exfoliation reaction are analyzed. The latest research progress on layered titanates and their modified products in the fields of photocatalysis, adsorption, electrochemistry, and other applications is summarized. Finally, the future development of layered titanate and its exfoliated product two-dimensional nanosheets is proposed.

Selective Cleavage of the Strong or Weak C-C Bonds in Biphenylene Enabled by Rare-Earth Metals.

Selective cleavage of C-C bonds within arene rings is of great interest but remains elusive, especially for the molecules possessing the active and inert C-C bonds. Here, we report that the active and inert C-C bonds of biphenylene could be controllably cleaved by the reaction of biphenylene, potassium graphite, and rare-earth complexes with different metal centers. For scandium, the bond activation occurs at the Caryl-Caryl single bond, yielding 9-scandafluorene. For Lu, the reaction goes through ring contraction of the aromatic ring in biphenylene to provide benzopentalene dianionic lutetium. The origin of the selectivity and the reaction mechanism were illustrated by the isolation of intermediates and DFT calculations.

Progress of Azametallacyclopentadienes in the New Century.

As the key intermediates in metal-promoted/catalyzed C-C bond coupling reactions of nitriles and alkynes, azametallacyclopentadienes, M(N=CR1 -CR2 =CR3 ), are an important class of azametallacycles. Although the first authentic azametallacyclopentadienes were documented in 1986, their chemistry towards solid-state structures, intrinsic reactivity, and synthetic application was rarely investigated for a long time. At the beginning of this century, seminal works about the applications of azametallacyclopentadienes in the synthesis of heterocycles, including multi-substituted pyridines, isoquinolines, furans, and pyrroles were reported. Subsequently, a series of new complexes with this motif, namely the Group 4, aluminum, actinide, and rare-earth azametallacyclopentadienes were isolated and structurally characterized. Among them, the rare-earth azametallacyclopentadiene expresses high reactivity towards unsaturated molecules, such as nitriles, isocyanides, and Mo(CO)6 to provide novel fused metallacycles. In this Concept, we reviewed the advances in the preparation, reactivity, and synthetic application of azametallacyclopentadienes in the past twenty years.

Photochemical Benzylation of White Phosphorus.

Organophosphorus compounds (OPCs) have wide application in organic synthesis, material sciences, and drug discovery. Generally, the vast majority of phosphorus atoms in OPCs are derived from white phosphorus (P4). However, the large-scale preparation of OPCs mainly proceeds through the multistep and environmentally toxic chlorine route from P4. Herein, we report the direct benzylation of P4 promoted by visible light. The cheap and readily available benzyl bromide was used as a benzylation reagent, and tetrabenzylphosphonium bromide was directly synthesized from P4. In addition, the metallaphotoredox catalysis strategy was applied to functionalize P4 for the first time, which significantly improved the application range of the substituted benzyl bromide.

Insight into the Ligand-to-Ligand Charge-Transfer Process in Rare-Earth-Metal Diradical Complexes.

While a ligand-to-ligand charge-transfer (LLCT) process is an important way to understand the interactions between metal-bridged radicals for late-transition-metal complexes, there is little clear and evident observation of the LLCT process for rare-earth-metal complexes. In this work, rare-earth-metal diradical complexes supported by diazabutadiene (DAD) ligands [(DAD)2RE(BH4)] [RE = Yb (1), Sm (2)] were synthesized and studied. The coordination geometries of 1 and 2 are different due to the different ionic radii. Reduction of 1 or 2 generated monoradical complexes, with one of their DAD radical anions being reduced. In all of the complexes, Sm and Yb remain at the 3+ valence state. In their UV-vis spectra, the LLCT transition of 1 could be clearly observed, but complex 2 did not show the same transition. These results could be related to the geometric structures of the complexes as well as exchange coupling between diradicals, thus clearly expanding the model for late-transition-metal-bridged diradicals to rare-earth systems experimentally.

Uniportal versus multiportal video-assisted thoracoscopic segmentectomy for non-small cell lung cancer: a systematic review and meta-analysis.

It remains controversial whether one-port video-assisted thoracoscopic surgery (VATS) or multiportal VATS is better for segmentectomy in patients with early non-small cell lung cancer (NSCLC). We conducted this meta-analysis of eight published studies to compare the clinical effectiveness and safety of the two surgical approaches. The uniportal group had a shorter postoperative hospital stay (mean difference (MD): - 0.40, 95% CI [- 0.71 to - 0.08] days, p = 0.01), lower postoperative pain scores on day 3 (MD: - 0.90, 95% CI [- 1.26 to - 0.54], p < 0.00001) and day 7 (MD: - 0.33, 95% CI [- 0.62 to - 0.04], p = 0.02), fewer days of chest tube drainage (MD: - 0.47, 95% CI [- 0.78 to - 0.15] days, p = 0.004), and a smaller wound (MD: - 0.73, 95% CI [- 1.00 to - 0.46] cm, p < 0.00001) than the multiportal group. However, there were no significant differences between the groups in complications, operative times, resected lymph nodes, resected lymph node stations, blood loss, postoperative pain scores on days 1, 2, 30, overall survival (OS), or disease-free survival (DFS). The most common complications were prolonged air leakage (10.29%), bleeding (8.82%), vascular injury (7.14%), empyema (5.88%), and arrhythmia (5.26%) in the uniportal group. Overall, uniportal VATS appears to be better than multiportal VATS for segmentectomy in patients with NSCLC, with better postoperative outcomes and similar survival rates.

Preoperative hypoalbuminemia in patients undergoing cardiac surgery: a meta-analysis.

The preoperative serum albumin level has been shown to be associated with adverse postoperative complications, meaning that hypoalbuminemia may also be a risk factor. We performed a meta-analysis to evaluate the association of serum albumin levels with survival and complication rates after cardiac surgery. Relevant articles were identified through seven databases. Twenty studies with 22553 patients (hypoalbuminemia group, n = 9903; normal group, n = 12650) who underwent cardiac surgery met the inclusion criteria after screening. The primary outcomes were that hypoalbuminemia was significantly correlated with serious long-term all-cause mortality (hazard ratio [HR]: 1.95 [1.54-2.48]; P < 0.00001) and increased mortality (risk ratio [RR] = 1.91 [1.61-2.27], P < 0.00001). Hypoalbuminemic patients with cardiopathy were more likely to suffer postoperative complications (bleeding, infections, renal injury, and others) than those whose serum albumin levels were normal. Furthermore, hypoalbuminemia increased the time in the intensive-care unit (ICU) (mean difference [MD] = 1.18 [0.49-1.87], P = 0.0008), length of hospital stay (LOS) (MD = 3.34, 95% CI: 1.88-4.80, P < 0.00001), and cardiopulmonary bypass time (CPB) (MD = 12.40 [1.13-23.66], P = 0.03). Hypoalbuminemia in patients undergoing cardiac surgery appears to have a poor all-cause mortality or increased risk of complications. Adjusted perioperative serum albumin levels and treatment strategies for this high-risk population have the potential to improve the survival.

Overview of 1,5-Selective Click Reaction of Azides with Alkynes or Their Synthetic Equivalents.

Nowadays, the click reaction of azides with alkynes has evolved rapidly and become one of the most efficient methods to synthesize 1,2,3-triazoles, which are an important class of N-containing heterocycles. While the 1,4-selective click reaction of azides with alkynes is well established to synthesize 1,4-substituted 1,2,3-triazoles, the corresponding 1,5-selective click reaction for the generation of 1,5-substituted-1,2,3-triazoles is much less explored, and there is no systematic review for the 1,5-selective click reaction. This timely review summarizes the discovery and development of 1,5-selective click reactions of azides with alkynes for the synthesis of 1,5-substituted 1,2,3-triazoles. The 1,5-selective click reactions will be divided into three types according to the critical reactive intermediates: metallacyclic intermediates, acetylide intermediate, and formal 1,5-selective azide-alkyne cycloaddition. The related mechanistic studies will also be involved in this review.

Metalla-aromatics: Planar, Nonplanar, and Spiro.

ConspectusThe concept of aromaticity is one of the most fundamental principles in chemistry. It is generally accepted that planarity is a prerequisite for aromaticity, and typically the more planar the geometry of an aromatic compound is, the stronger aromatic it is. However, it is not always the case, particularly when transition metals are involved in conjugation and electron delocalization of aromatic systems, i.e., metalla-aromatics. Because of the intrinsic nature of transition-metal orbitals, besides planar geometries, the most stable molecular structures of metalla-aromatic compounds could take nonplanar and even spiro geometries. In this Account, we outline several unprecedented types of metalla-aromatics developed recently in our research group.Around seven years ago, we found that 1,4-dilithio-1,3-butadienes, dilithio reagents with π-conjugation, could function as non-innocent ligands and react with low-valent transition-metal complexes, generating monocyclic metalla-aromatic compounds. Later on, by taking advantage of the unique behavior of dilithio reagents and the intrinsic nature of different transition metals, we have synthesized a series of metalla-aromatic compounds, of which four types are discussed here, and each of them represents the first of its kind. First, nearly planar aromatic dicupra[10]annulenes, a 10 π-electron aromatic system with two bridging Cu atoms participating in the orbital conjugation and electron delocalization, are synthesized by annulating two dilithio reagents with two Cu(I) complexes.Second, four kinds of spiro metalla-aromatics, featuring planar (with Pd, Pt, or Rh as the spiro atom) geometry with a whole 10π aromatic system, octahedral (tris-spiro metalla-aromatics with V as the spiro atom) geometry with an entire 40π Craig-Möbius aromatic system, tetrahedral (with Mn as the spiro atom) geometry having two independent and perpendicular 6π planar aromatic rings, and tetrahedral (with Mn as the spiro atom) geometry with one planar and one nonplanar 6π aromatic rings, respectively, are generated. In sharp contrast to spiroaromaticity with carbon acting as the spiro atom described in Organic Chemistry, the metal spiro atom herein takes part in orbital conjugation and electron delocalization.Third, nonplanar aromatic butadienyl diiron complexes are realized. Different from planar aromatic systems featuring delocalized π-type overlap, this nonplanar metalla-aromaticity is achieved by the novel σ-type overlap between the two Fe 3dxz orbitals and the butadienyl π orbital, forming a 6π aromatic system. Fourth, dinickelaferrocene, a ferrocene analogue with two aromatic nickeloles, is synthesized from our monocyclic aromatic dilithionickelole and FeBr2. The aromaticity of dinickelaferrocene and its nickelole ligands is realized by electron back-donation from the Fe 3d orbital to the π* orbital of nickeloles, which also deepens our understanding of the origin of aromaticity.The search for unprecedented and exciting aromatic systems, particularly with transition metals being involved, will continue to drive this intriguing research field forward. Given the synthetic strategies and various types of metalla-aromatics developed and described, diversified metalla-aromatics of interesting structures and reaction chemistry, novel chemical bonding modes, and useful functions can be expected.

A novel pyroptosis-related lncRNA prognostic signature associated with the immune microenvironment in lung squamous cell carcinoma.

BACKGROUND: A growing body of evidence suggests that pyroptosis-related lncRNAs (PRncRNAs) are associated with the prognoses of tumor patients and their tumor immune microenvironments. However, the function of PRlncRNAs in lung squamous cell carcinoma (LUSC) remains unclear. METHODS: We downloaded the transcriptome and clinical information of 551 LUSC samples from the The Cancer Genome Atlas (TCGA) database and randomly separated patients with complete information into two cohorts. Based on the training cohort, we developed a pyroptosis-related signature. We then examined the signature in the test cohort and all retained patients. We also clustered two risk groups in each cohort according to the signature and performed survival analysis, functional analysis, tumor immune microenvironment analysis and drug sensitivity analysis. RESULTS: A prognostic signature containing five PRlncRNAs (AP001189.1, PICART1, LINC02555, AC010422.4, and AL606469.1) was developed. A principal component analysis (PCA) indicated better differentiation between patients with different risk scores. Kaplan-Meier (K-M) analysis demonstrated poorer survival among patients with higher risk scores (P < 0.001). A receiver operating characteristic (ROC) curve analysis provided evidence confirming the accuracy of the signature, and univariate (p = 0.005) and multivariate (p = 0.008) Cox regression analyses confirmed the independent value of the risk score in prognoses. Clinical subgroup validation indicated that the signature was more suitable for patients with early-stage LUSC. We also created a nomogram to increase the accuracy of the prediction. Moreover, functional analysis revealed that pathways related to tumor development and pyroptosis were enriched in the high-risk group. Furthermore, the prognostic signature was proven to be a predictor of sensitivity to immunotherapy and chemotherapy. CONCLUSIONS: We developed a novel pyroptosis-associated signature with independent value for the prognosis of LUSC patients. PRlncRNAs are closely associated with the tumor immune microenvironment in LUSC and might offer new directions for immunotherapy.

Crizotinib versus Alectinib for the Treatment of ALK-Positive Non-Small Cell Lung Cancer: A Systematic Review and Meta-Analysis.

BACKGROUND: Crizotinib and alectinib are the 2 most commonly used anaplastic lymphoma kinase (ALK) inhibitors for ALK-positive non-small cell lung cancer (NSCLC). We compared their antitumor efficacies and adverse effects based on a pooled analysis of the ALEX, ALESIA, and J-ALEX clinical trials. METHODS: Seven databases were searched for eligible articles. The primary endpoints included overall survival (OS), progression-free survival (PFS), central nervous system (CNS)-PFS, drug responses, and adverse effects (AEs). RESULTS: Seven articles on 3 randomized controlled clinical trials (ALEX, ALESIA, and J-ALEX) that included 697 patients were included. Compared with crizotinib, alectinib exhibited superior efficacy in PFS (HR [hazard ratio]: 0.35 [0.25-0.49], p < 0.00001), OS (HR: 0.66 [0.47-0.92], p = 0.02), CNS-PFS (HR: 0.17 [0.11-0.24], p < 0.00001), duration of response (HR: 0.31 [0.23-0.42], p < 0.00001), objective response rate (risk ratio [RR]: 0.87 [0.80-0.94], p = 0.0003), partial response (RR: 0.88 [0.81-0.96], p = 0.004), and grade 3-5 AEs (RR: 1.43 [1.09-1.87], p = 0.009). Additionally, compared with crizotinib, alectinib exhibited a survival advantage that increased with its prolongation of survival time. The disease control rate, complete response, and total AEs were comparable between the 2 groups. The crizotinib group reported higher rates of constipation, nausea, diarrhea, vomiting, peripheral edema, dysgeusia, visual impairment, and levels of alanine aminotransferase and aspartate aminotransferase as well as greater decreases in appetite and neutrophil count. CONCLUSIONS: In both antitumor efficacy and safety, alectinib appears to be superior to crizotinib for the treatment of ALK-positive NSCLC.

The efficacy and toxicity of maintenance therapy with bevacizumab plus pemetrexed versus bevacizumab/pemetrexed alone for stage IIIB/IV nonsquamous non-small cell lung cancer: A meta-analysis of randomized controlled trials.

WHAT IS KNOWN AND OBJECTIVE: Whether maintenance therapy with bevacizumab (Bev) + pemetrexed (Pem) can achieve greater clinical benefits than Bev or Pem alone for stage IIIB/IV nonsquamous non-small cell lung cancer (NSCLC) remains unclear. We assessed the antitumour effect and toxicity of maintenance Bev+Pem versus maintenance with single-agent Bev/Pem in this meta-analysis. METHODS: Appropriate randomized controlled trials (RCTs) were screened using electronic databases (Google Scholar, PubMed, Embase, Scopus, ScienceDirect, Ovid MEDLINE, Cochrane and Web of Science). The endpoints were progression-free survival (PFS), overall survival (OS) and adverse events (AEs). RESULTS AND DISCUSSION: We included six RCTs that contained 2,447 patients receiving induction therapy with platinum-based combination therapies. The maintenance therapy Bev+Pem group had prolonged PFS (HR = 0.74, 95% CI 0.69-0.80, p < 0.00001) and OS (HR = 0.91, 95% CI 0.83-0.99, p = 0.02) compared with the Bev/Pem group. Moreover, we further analysed the PFS rate (PFSR) and OS rate (OSR) and found that the Bev+Pem group exhibited improved PFSR-0.5y, PFSR-1y, PFSR-1.5y, PFSR-2y and OS-2y, with preferable trends in OS-1y, OS-3y and OS-4y compared with the Bev/Pem single-agent maintenance therapy. In addition, subgroup analyses indicated that the Bev+Pem group had greater PFS and OS among patients aged <65 years, patients with an Eastern Cooperative Oncology Group (ECOG) score of 0, and patients who never smoked. Regarding adverse events (AEs), the Bev+Pem group exhibited an increased occurrence of anaemia, fatigue, thrombocytopenia and anorexia. WHAT IS NEW AND CONCLUSION: For stage IIIB/IV nonsquamous NSCLC patients, maintenance therapy with Bev+Pem offers an increased survival outcome (PFS, OS) compared with monotherapy. However, the increased incidence of AEs should not be neglected.

Efficacy and safety of empagliflozin at different doses in patients with type 2 diabetes mellitus: A network meta-analysis based on randomized controlled trials.

WHAT IS KNOWN AND OBJECTIVE: As an oral hypoglycaemic drug that significantly reduces cardiovascular risk, empagliflozin is often used in patients with type 2 diabetes mellitus (T2DM). However, the dosage and administration of empagliflozin are still controversial clinically. To determine the most appropriate dose, we performed this network meta-analysis. METHODS: We identified randomized controlled trials (RCTs) about empagliflozin from eight databases. We analysed the pharmacodynamics, adverse effects (AEs), and pharmacokinetics of empagliflozin at different doses. RESULTS: We identified 8264 articles, of which 23 RCTs with 10518 patients were included. Regarding haemoglobin A1c (HbA1c) and fasting plasma glucose (FPG), high-daily doses (10, 25, 50 mg) were significantly better than low doses (1, 2.5, 5 mg). For total AEs, there was a dose-response trend in which safety decreased with increasing doses. According to SUCRA sequencing, the order for lowering HbA1c was 25 > 50 > 10 > 5 > 1 mg, for lowering FPG was 50 > 25 > 10 > 5 > 2.5 > 1 mg and for safety was 1> 5 > 10 > 25> 2.5 > 50 mg. When considering HbA1c, FPG and total AEs, we performed a hierarchical cluster analysis and network meta-analysis to find that 25 mg performed best among different doses, which was more significant after long-term use (≥ 12 weeks). Pharmacokinetic parameters exhibited significant dose-response relationships. WHAT IS NEW AND CONCLUSION: High-daily doses (10, 25, 50 mg) had better efficacy than low doses (1, 2.5, 5 mg). When considering HbA1c, FPG and total AEs, 25 mg performed best among the different doses in patients with T2DM.

Effects of preoperative needle biopsy for lung cancer on survival and recurrence: a systematic review and meta-analysis.

Needle biopsy (NB) is used for the diagnosis of lung cancer, but there is still controversy about its effect on the prognosis after surgery. We conducted this meta-analysis to compare the prognosis of lung cancer patients who underwent preoperative NB with that of those who did not. We systematically searched seven databases and Google Scholar for eligible studies. Recurrence-free survival (RFS) and overall survival (OS) were analyzed as primary outcome measures. Nine articles with a collective total of 13,541 patients (NB group, n = 4550; non-NB group, n = 8991) were included in our meta-analysis. OS [hazard ratio (HR) = 1.43 (0.96, 2.12), p = 0.08] and RFS (HR = 1.59 [1.25, 2.01], p = 0.0001) tended to be better in the non-NB group than in the NB group. Pleural recurrence (risk ratio (RR) = 2.40 [1.42, 4.07], p = 0.001) was significantly lower in the non-NB group than in the NB group. The recurrence analysis data did not reach significance, but the overall trend was better for the non-NB group. These findings demonstrate that NB is detrimental to the survival prognosis of lung cancer patients and increases the chance of pleural recurrence.

Selective Coupling of Lanthanide Metallacyclopropenes and Nitriles via Azametallacyclopentadiene and η2-Pyrimidine Metallacycle.

Exploring new lanthanide metallacycles and finding their unique chemistry different from the analogues of transition metals are of great interest and importance. In this work, we reported the synthesis, characterization, and reactivity toward nitriles of two lanthanide metallacyclopropenes: lutetacyclopropene 2a and dysprosacyclopropene 2b. The selective coupling of 2a and three molecules of PhCN was found for the first time to provide the unexpected fused lutetacycle 3a with one 1,6-dihydropyrimidine ring. Mechanistic studies by DFT calculations reveal that the triple insertion of PhCN into 2a proceeds through four key steps: the insertion of the first PhCN into 2a giving azalutetacyclopentadiene IM1, the insertion of the second PhCN into the Lu-N bond of IM1, the intramolecular electrocyclization providing a highly strained η2-pyrimidine metallacycle, and the insertion of the third PhCN into the Lu-Csp3 bond. Isolation and characterization of two active intermediates, azalutetacyclopentadiene IM1 and η2-pyrimidine dysprosacycle, provide critical evidence for the formation of 3a. Furthermore, IM1 was also reported to react with TMSCN, isocyanides, or W(CO)6 to furnish the fused [4,5] lutetacycles. The chemistry of two lanthanide metallacyclopropenes with nitriles is significantly different from these metallacyclopropenes of scandium and other metals. Most notably, the azalutetacyclopentadienes, η2-pyrimidine complex, and other metallacycles all represent the first examples in rare-earth organometallic chemistry; the formation of these new lutetacycles provides concrete evidence for understanding the mechanism of transition metal promoted or catalyzed [2+2+2] cycloaddition between alkynes and nitriles.

Insertion Chemistry of Lutetacyclopropene toward Unsaturated C-O/C-N Bonds.

Although the reaction chemistry of transition metallacyclopropenes has been well-established in the last decades, the reactivity of rare-earth metallacyclopropenes remains elusive. Herein, we report the reaction of lutetacyclopropene 1 toward a series of unsaturated molecules. The reaction of 1 with one equiv. of PhCOMe, Ar1 CHO (Ar1 =2,6-Me2 C6 H3 ), W(CO)6 , and PhCH=NPh provided oxalutetacyclopentenes, metallacyclic lutetoxycarbene, and azalutetacyclopentene via 1,2-insertion of C=O, C≡O, or C=N bonds into Lu-Csp2 bond, respectively. However, the reaction between 1 and Ar2 N=C=NAr2 (Ar2 =4-MeC6 H4 ) gave an acyclic lutetium complex with a diamidinate ligand by the coupling of one molecule of 1 with two carbodiimides, irrespective of the amount of carbodiimide employed. More interestingly, when 1 was treated with two equiv. of Ar1 CHO, the reductive coupling of two C=O bonds was discovered to give a lutetium pinacolate complex along with the release of tolan. Remarkably, the reactivity of 1 is significantly different from that of scandacyclopropenes; these metallacycles derived from 1 all represent the first cases in rare-earth organometallic chemistry.