Tandem Ring Research Articles

Heterobimetallic Pd–Sn Catalysis: A Suzuki, Tandem Ring-Closing Sequence toward Indeno[2,1-b]thiophenes and Indeno[2,1-b]indoles

Indeno[2,1-b]thiophene and indeno[1,2-b]indole motifs have been obtained in moderate to good yields from easily available substituted boronic acids, 2-bromo aryl/vinyl aldehydes, and nucleophiles such as arenes/heteroarenes and others using a catalytic combination of bimetallic "Pd-Sn" and AgPF(6). This formal three-component coupling involves a Suzuki reaction followed by nucleophile assisted tandem ring closure. The sequential synthesis of substituted heterocycle-fused indenes, benzofluorene, and fluorenes was also accomplished.

The usefulness of an independent patient-specific treatment planning verification method using a benchmark plan in high-dose-rate intracavitary brachytherapy for carcinoma of the uterine cervix

To develop an easy independent patient-specific quality assurance (QA) method using a benchmark plan for high-dose-rate intracavitary brachytherapy for cervix cancer, we conducted benchmark treatment planning with various sizes and combinations of tandem-ovoid and tandem-cylinder applications with ‘ideal’ geometry outside the patient. Two-dimensional-based treatment planning was conducted based on the Manchester method. We predicted the total dwell time of individual treatment plans from the air kerma strength, total dwell time and prescription dose of the benchmark plan. In addition, we recorded the height (dh), width (dw) and thickness (dt) covered with 100% isodose line. These parameters were compared with 169 and 29 clinical cases for tandem-ovoid or tandem-cylinder cases, respectively. With regard to tandem-ovoid cases, differences in total dwell time, dh, dt and dw between benchmark and individual plans were on average –0.2% ± 3.8%, –1.0 mm ± 2.6 mm, 0.8 mm ± 1.3 mm and –0.1 mm ± 1.5 mm, respectively. With regard to tandem-cylinder cases, differences in total dwell time, dhfront (the distance from tandem tip to tandem ring), dt and dw between benchmark and individual plans were on average –1.5% ± 3.1%, –1.5 mm ± 4.9 mm, 0.1 mm ± 1.0 mm and 0.2 mm ± 0.8 mm, respectively. Of two cases, more than 13% differences in total dwell time were observed between benchmark plans and the clinical cases, which turned out to be due to the use of the wrong source position setting. These results suggest that our method is easy and useful for independent verification of patient-specific treatment planning QA.

A facile and rapid one-step synthesis of 8-substituted xanthine derivatives via tandem ring closure at room temperature

N-Bromo succinimide (NBS) was found to be an efficient and regioselective reagent in combination with AIBN for an unprecedented, facile and rapid one-step synthesis of 8-substituted xanthine derivatives at room temperature. The inexpensive, nontoxic and readily available NBS efficiently promoted the condensation of several aryl/cycloaryl/heteroaryl aldehydes with 5,6-diamino-1,3-dimethyluracils in presence of catalytic amount of AIBN in a single step via radical chain reaction. The notable advantages of this protocol were short reaction time, milder reaction conditions, simple work-up procedure, no requirement for chromatographic separation, use of non-hazardous reagent/solvent and applicable to a variety of substrates.

Access to l- and d-Iminosugar C-Glycosides from a d-gluco-Derived 6-Azidolactol Exploiting a Ring Isomerization/Alkylation Strategy

A flexible synthetic access to six-membered L- and D-iminosugar C-glycosides is reported starting from the easily available 6-azido-6-deoxy-2,3,4-tri-O-benzyl-D-glucopyranose precursor. This methodology involves a highly diastereoselective tandem ring enlargement/alkylation and a stereocontrolled ring contraction. It allows an efficient synthesis of iminosugar C-glycosides displaying structural diversity at both C-1 and C-6.

Examination of the Energy Efficiency of the Continuation Tandem Ring Mill

In this study, a continuation high-impact pulverizing vibration mill, which replaces the ball medium with a ring shape medium called tandem ring was developed for effective pretreatment of lignocellulosic biomass to produce the bio-ethanol. The pulverizing effects of the mill were investigated through a repeatedly pulverizing examination of Japanese cedarwood on its particle size distribution, moisture content and enzymatic saccharification efficiency. As the results, average particle size was reached around 22μm at the ten times pulverization at 1600cpm. An enzymatic saccharification efficiency of holocellulose was reached over 50% at the twenty times pulverization. Additionally its power consumption was one-third as large as the conventional the batch-type high-impact pulverizing vibration mill. Therefore the continuation high-impact pulverizing vibration mill had a better pulverizing performance for lignocellulosic biomass pretreatment.

Efficient synthesis of isochromanones and isoquinolines via Yb(OTf)3-catalyzed tandem oxirane/aziridine ring opening/Friedel–Crafts cyclization

The first example of Yb(OTf)(3)-catalyzed tandem ring opening/Friedel-Crafts cyclization of oxiranyl and aziridinyl ketones via selective C-C bond cleavage under mild conditions was developed. Isochromanones and isoquinolines are formed in reasonable yields, which often serve as building blocks for complex chemical synthesis.

ChemInform Abstract: Tandem Ring Opening/Cyclization of Vinylcyclopropanes: A Facile Synthesis of Chiral Bicyclic Amidines.

AbstractTreatment of vinylcyclopropane derivatives with nitriles and chloramine‐T (II) results in a tandem ring opening/cyclization through a Ritter‐type rearrangement to afford enantiopure bicyclic amidines.

Identifying afterloading PDR and HDR brachytherapy errors using real-time fiber-coupled Al2O3:C dosimetry and a novel statistical error decision criterion

Background and purposeThe feasibility of a real-time in vivo dosimeter to detect errors has previously been demonstrated. The purpose of this study was to: (1) quantify the sensitivity of the dosimeter to detect imposed treatment errors under well controlled and clinically relevant experimental conditions, and (2) test a new statistical error decision concept based on full uncertainty analysis. Materials and methodsPhantom studies of two gynecological cancer PDR and one prostate cancer HDR patient treatment plans were performed using tandem ring applicators or interstitial needles. Imposed treatment errors, including interchanged pairs of afterloader guide tubes and 2–20mm source displacements, were monitored using a real-time fiber-coupled carbon doped aluminum oxide (Al2O3:C) crystal dosimeter that was positioned in the reconstructed tumor region. The error detection capacity was evaluated at three dose levels: dwell position, source channel, and fraction. The error criterion incorporated the correlated source position uncertainties and other sources of uncertainty, and it was applied both for the specific phantom patient plans and for a general case (source-detector distance 5–90mm and position uncertainty 1–4mm). ResultsOut of 20 interchanged guide tube errors, time-resolved analysis identified 17 while fraction level analysis identified two. Channel and fraction level comparisons could leave 10mm dosimeter displacement errors unidentified. Dwell position dose rate comparisons correctly identified displacements ⩾5mm. ConclusionThis phantom study demonstrates that Al2O3:C real-time dosimetry can identify applicator displacements ⩾5mm and interchanged guide tube errors during PDR and HDR brachytherapy. The study demonstrates the shortcoming of a constant error criterion and the advantage of a statistical error criterion.

ChemInform Abstract: Palladium‐Catalyzed Tandem Reaction to Construct Benzo[c]phenanthridine: Application to the Total Synthesis of Benzo[c]phenanthridine Alkaloids.

AbstractA Pd‐catalyzed tandem ring opening—cross coupling—cyclization reaction of o‐iodobenzoates (I) with azabicycle (II) is the key step in the synthesis of benzophenanthridine alkaloids like avicine (IVa), chelerythrine (IVb) or nitidine (IVc).

SU-E-T-368: Semi-Independent Plan Verification Method for High-Dose-Rate Intracavitary Brachytherapy Using Benchmark Plan

Purpose: We propose very simple and easy semi‐independent verification method in HDR intracavitary brachytherapy. Methods: We conducted benchmark plans of various sizes of tandem‐ovoid and tandem‐cylinder applications that were constructed with ‘ideal’ form at outside the body by one radiation oncologist.Treatment plans were conducted based on Manchester system with PLATO using semi orthogonal films of these applicator settings. We predicted the dwell time of every treatment from the air kerma strength and total dwell time of the benchmark plans. In addition, we compared the height (dh), width (dw), and thickness (dt) of 100% isodose line of clinical cases with those of benchmark plans. In this study, 49 and 29 datasets were analyzed for tandem‐ovoid and tandem‐cylinder cases, respectively. Results: With regard to tandem‐ovoid cases, differences of total dwell time, dh, dt and dw between benchmark plans and clinical cases were on average 0.3%±3.2%, −0.5mm±2.4 mm, 0.7mm±2.4mm, and − 0.3mm±1.0mm, ranging from −8.3% to 7.5%, −6.2 mm to 5.3mm, −1.0mm to 2.7mm, and −1.7mm to 2.4mm, respectively. With regard to tandem‐cylinder cases, differences of total dwell time, dhfront which is the distance from tandem tip to tandem ring, dt, and dw between benchmark plans and clinical cases tandem‐cylinder settings were on average −1.5%±3.1%, − 1.5mm±4.9mm, 0.1mm±1.0mm, and 0.2mm±0.8mm, ranging from −13.0% to 0.4%, −19.0mm to 4.0mm, −1.3mm to 4.3mm, and −0.4mm to 3.9mm, respectively. Two cases were founded to be planning mistakes in which more than 10% differences of total dwell time and 15mm differences of dhfront were observed between benchmark plans and the clinical cases. Conclusions: This method is very simple and easy but can be used for quick check of treatment planning and can find the planning mistakes.

Tandem Ring Opening/Cyclization of Vinylcyclopropanes: A Facile Synthesis of Chiral Bicyclic Amidines

Ring auf, Ring zu: Eine bromkatalysierte Tandemsequenz aus Ringöffnung und Cyclisierung von bicyclischen Vinylcyclopropanen mit Chloramin-T ([TsNCl]Na) liefert chirale bicyclische Amidinderivate in guten Ausbeuten. Auf Grundlage der experimentellen Beobachtungen wird ein plausibler Mechanismus vorgeschlagen. Ts=p-Toluolsulfonyl.

Tandem Ring Opening/Cyclization of Vinylcyclopropanes: A Facile Synthesis of Chiral Bicyclic Amidines

An open and shut case: An interesting bromine-catalyzed tandem ring opening/cyclization reaction of bicyclic vinylcyclopropanes with chloramine-T ([TsNCl]Na) has been demonstrated to furnish chiral bicyclic amidine derivatives in good yield. A plausible mechanism has been proposed based on the experimental observations. Ts=p-toluenesulfonyl.

First Total Synthesis of 3-Epi-calystegin B2

A straightforward chiral pool synthesis for a non-natural calystegin, 3-epi-B2, is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. Compared to calystegin B2, the target compound is no longer an inhibitor for a β -glycosidase hence proving that an equatorial hydroxyl group at position C-3 is necessary for a tight binding of calystegins into the active site of β -glycosidases.

F115 連続式タンデムリング粉砕機のエネルギー効率の検討(OS3 バイオマス・新燃料・環境技術)

In this study, a continuation high-impact pulverizing vibration mill, which replaces the ball medium with a ring shape medium called tandem ring was developed for effective pretreatment of lignocellulosic biomass to produce the bio-ethanol. The pulverizing effects of the mill were investigated through a repeatedly pulverizing examination of Japanese cedarwood on its particle size distribution, moisture content and enzymatic saccharification efficiency. As the results, average particle size was reached around 22μm at the ten times pulverization at 1600cpm. An enzymatic saccharification efficiency of holocellulose was reached over 50% at the twenty times pulverization. Additionally its power consumption was one-third as large as the conventional the batch-type high-impact pulverizing vibration mill. Therefore the continuation high-impact pulverizing vibration mill had a better pulverizing performance for lignocellulosic biomass pretreatment.

Unsymmetrical Ru-NHC catalysts: a key for the selective tandem Ring Opening–Ring Closing alkene Metathesis (RO–RCM) of cyclooctene

Dissymmetry for selectivity: NHC ligand with two different pendant group allows the selective formation of cyclic oligomers in place of polymers opening new strategy to generate macrocycles.

ChemInform Abstract: Synthesis of Isoquinoline Derivatives by a Tandem Aza-Wittig/ Electrocyclization Strategy and Preparation of the Unknown 1,9- Diazaphenalene Ring by a Consecutive Electrocyclic Ring Closure/ Claisen Rearrangement/ Intramolecular Amina

Treatment of iminophosphrane 3, derived from ethyl α-azido-2-(allyloxy) cinnamate, with aromatic isocyanates in toluene at 150 o C leads to the corresponding isoquinoline derivatives 5 by a tandem electrocyclic ring closure/Claisen rearrangement of the intermediate carbodiimide. Fremy's salt promoted oxidation of compounds 5 yields the 5,8-isoquinolinequinone allides 6, which by heating undergo cyclization to 2H-pyrano [2,3-f] isoquinolines isocyanates to give the corresponding carbodiimides, which by thermal treatment at 150 o C undergo a consecutive electrocyclic ring closure/Claisen rearrangement/intramolecular amination process to give 1,9-diazaphenalene derivatives

ChemInform Abstract: A Concise and Enantioselective Approach to Cyclobutanones by Tandem Asymmetric Epoxidation and Enantiospecific Ring Expansion of Cyclopropylidene Alcohols. An Enantiocontrolled Synthesis of (+)- and ( -)-α-Cuparenones.

A tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-α-cuparenones

Regioselective Tandem Ring Closing/Cross Metathesis of 1,5‐Hexadien‐3‐ol Derivatives: Application to the Total Synthesis of Rugulactone

AbstractA tandem ring‐closing metathesis/cross‐metathesis procedure was devised for the synthesis of various pyrones. The reaction occurred with high regioselectivity and E stereocontrol of the lateral unsaturated chain. This process was applied to the synthesis of rugulactone, an inhibitor of the nuclear factor NF‐κB according to a four‐step sequence.

ChemInform Abstract: Novel Synthesis of 4-Oxo-1-isoquinolone Derivatives Utilizing Inter- and Intramolecular Tandem Carbopalladation-Heterocyclic Ring Expansion.

Abstract The palladium(0)-catalyzed inter- and intramolecular carbopalladation-heterocyclic ring expansion employing allenic alcohols and aryl iodides provides a novel and facile route to 4-oxo-1-isoquinolone derivatives in reasonable to high yields.

First Total Synthesis of a Fluorinated Calystegin

A straightforward chiral pool synthesis for the first fluorinated calystegin is described. Key steps of this synthesis include an ultrasound-assisted Zn-mediated tandem ring opening reaction followed by a Grubbs’ catalyst-mediated ring closure metathesis reaction. The target compound is a selective and competitive inhibitor for a β -glycosidase.