Synthesis and structure of m-terphenyl-based cyclophanes with nitrogen intra-annular functional groups

[structure: see text] Herein we describe an efficient synthesis of cyclophanes comprised of intra-annular nitrogen functional groups through a template-promoted cyclization by ring-closing metathesis (RCM). The synthesis proceeds through condensation of meta-styryl anilines with acenaphthenequinone to form the templates, followed by RCM with Grubb's second-generation catalyst to afford cyclophanes with internal alpha-diimine functionality. Prolonged hydrogenation efficiently removes the template to provide a macrocycle containing the diamine functionality.     

Growth of large KDP single crystals for UV spectrum range

The influence of various technological parameters of crystallization (acidity of growth solutions, crystallization temperature, growth rate, degree of solution purification) on the optical absorption of large KDP single crystals has been studied in the UV range of the spectrum. It is shown that the method of solvent recirculation with the use of the starting material with the microimpurity content not exceeding 5 × 10^?5 wt % and solution ultrafiltration under the optimum crystallization conditions (t_cr = 80°C, V_cr ～ (0.8–1.6) × 10^?6 cm/s, pH 4) enables one to grow KDP single crystals with cross sections up to 300 × 300 mm² and the transmission in the vicinity of the fundamental absorption edge λ = 200 nm) equal to 86%.     

The first synthesis of thieno[c]isoquinolines and an improved synthesis of phenanthridine and thieno[c]quinolines through pd(0) catalyzed coupling of ortho-formylarylboronic acids with functionalized aryl halides

All three isomeric hitherto unknown thieno[c]isoquinolines have been synthesized in high yields by the Pd(0)-catalyzed coupling of 2-formylbenzeneboronic acid with t-butyl-N-(ortho-halothienyl)carbaniates. When 2-bromoacetanilide, instead of 2-bromoaniline, was coupled with orth-formylarylboronic acids under Pd-catalysis, phenanthridine and thieno[c]quinolines were obtained in improved yields. Total assignments of ¹H nmr spectra of thieno[c]isoquinolines and thieno[c]quinolines are reported. Assignments are based on high resolution 300 MHz ¹H nmr spectra, two-dimentional ¹H-¹³C chemical shift correlation spectra and one-dimentional INADEQUATE ¹³C nmr spectroscopy.     

Evolution of Unit Fraction Conceptions in Two Fifth-Graders with a Learning Disability: An Exploratory Study

The literature seems limited in what is known about conceptual processes that underlie evolution of students with learning disabilities (SLD) conceptions of fractions. This exploratory study examines how a foundational scheme of unit fractions (1/n) may evolve through the mathematical activity of two fifth grade girls. We analyze data segments from episodes conducted during a teaching experiment grounded in the activity of iterating estimates of one person's equal share. Our findings include four distinct conceptual stages: (1) No Conception of the Nature of Adjustment to the Magnitude of a Unit Fraction, (2) Evolving Anticipation of the Nature of Adjustment but not of its Relative Amount, (3) Anticipation of the Nature of Adjustment with an Evolving Partial Amount, and (4) a Dual Anticipation of the Nature and Amount of Adjustment. Findings demonstrate each girl was able to use her constructed scheme to successfully solve and reason about novel problems. We discuss the need for more research to confirm the findings from this study, while offering a conjecture of the possibilities for more SLDs to advance their conceptions of fractions in future interventions.     

Carleman estimates and inverse problems for Dirac operators

We consider limiting Carleman weights for Dirac operators and prove corresponding Carleman estimates. In particular, we show that limiting Carleman weights for the Laplacian also serve as limiting weights for Dirac operators. As an application we consider the inverse problem of recovering a Lipschitz continuous magnetic field and electric potential from boundary measurements for the Pauli Dirac operator. M. Salo is supported by the Academy of Finland. L. Tzou is supported by the Doctoral Post-Graduate Scholarship from the Natural Science and Engineering Research Council of Canada. This article was written while L. Tzou was visiting the University of Helsinki and TKK, whose hospitality is gratefully acknowledged. The authors would like to thank András Vasy and Lauri Ylinen for useful comments.     

Partial data inverse problems for Maxwell equations via Carleman estimates

In this article we consider an inverse boundary value problem for the time-harmonic Maxwell equations. We show that the electromagnetic material parameters are determined by boundary measurements where part of the boundary data is measured on a possibly very small set. This is an extension of earlier scalar results of Bukhgeim–Uhlmann and Kenig–Sjöstrand–Uhlmann to the Maxwell system. The main contribution is to show that the Carleman estimate approach to scalar partial data inverse problems introduced in those works can be carried over to the Maxwell system.     

On the reaction of methoxide ion with bromoiodothiophenes

The reaction of 3-bromo-2-iodothiophene with sodium methoxide in methanol, pyridine or hexamethylphosphoric triamide and the same reaction of 4-bromo-2-iodo- and 4-bromo-3-iodo-thiophene in pyridine led to a halogen-dance, giving the same mixture of 3-bromothiophene, bromo-iodothiophenes, diiodo-bromothiophenes and triiodo-bromothiophenes. The reaction of all three isomeric bromo-iodothiophenes with sodium methoxide in methanol in the presence of cupric oxide gave 4-bromo-2-methoxythiophene.     

Studies of the reaction of 3-bromo-2,5-dimethylthiophene 1,1-dioxide with some organocopper reagents

The coupling reactions of some organocopper reagents with 3-bromo-2,5-dimethylthiophene 1,1-dioxide leading to 3-alkyl and 3-aryl substituted 2,5-dimethylthiophene 1,1-dioxides have been found to proceed in high yields (50–100%). The less stable organocopper reagents reacted faster and at lower temperatures than the more stable ones. It is more convenient to use alkylcopper than lithium dialkylcuprate reagents, which give higher yields without side reactions.     

The versatile chemistry of thiophenes: The effects of b-side contra c-side annelation on reactivity

The synthesis of the nine dithienopyridines and twenty-four thienonaphthyridines with angular annelation is described. They are all conveniently obtained by Pd(0)-catalysed couplings between heterocyclic o-formylboronic acids or o-formylstannyl derivatives with heterocyclic o-amino-halo derivatives. The effect of the use of silver oxide and cupric oxide as co-reagent is discussed. Differences in electrophilic substitution, metalation and cycloaddition of b- and c-fused isomers is treated. Theoretical calculations at the RHF/3–21G* level are in agreement with the orientation and reactivity in the nitration of dithieno[3,4-b:3′,4′-d] pyridine and dithieno[2,3-b:3′,2′-d] pyridine observed experimentally. The preparation of N-oxides of the above-mentioned ring-systems and their reactivity will also be discussed.     

Orientation effects in the nitration of the dithieno[b,d]pyridine N-oxides. Its dependence on acidity of the reaction medium

The nitration of three dithienopyridine-N-oxides was investigated. The regiochemistry of the reaction was dependent on the reaction conditions used. Under strongly acidic conditions the positional preference is similar for the N-oxides and free bases. However, under mildly acidic or neutral conditions a completely different substitution pattern was obtained. In the latter case those ring positions were substituted which are expected to be unfavored or forbidden in electrophilic substitution of the free bases. The structures of the nitro derivatives were proven by extensive use of ¹H and ¹³C nmr spectroscopy.