Highly Stereoselective Halocyclopropanation of α,β‐Unsaturated Amides

A convenient highly stereoselective synthesis of chloro‐ and bromocyclopropanamides from di‐ tri‐ or tetrasubstituted (E)‐ or (Z)‐α,β‐unsaturated amides with total or high stereoselectivity promoted by chromium dichloride or dibromide is described. The transformation of chlorocyclopropanamides into the corresponding ketones or amines is also reported. A mechanism to explain these transformations is proposed.     

The Dyeing Properties of Monoazo Reactive Disperse Dyes Derived from –Chloro–4–aminoacetophonone on Polyester Fibre Blends

The preparation of monoazo reactive disperse dyes from –chloro–4–aminoacetophenone and the dyeing properties of these dyes on polyester–cotton and polyester–wool blends are reported.     

Highly Reactive β-Dicalcium Silicate

Calcium silicate hydrate was prepared by hydrothermal reaction between calcium oxide and silica (C/S = 2.0) at a temperature of 205°–215°C and a pressure of 17–19 bar. This reaction with decomposition at 900°C produced highly reactive β-dicalcium silicate (specific surface area 4.55 m²/g) contaminated with small amounts of wollastonite as an impurity. Infrared spectral studies have shown that β-dicalcium silicate prepared at 900°C is less symmetric compared with the control prepared at 1450°C using boron trioxide as a stabilizer. The specific surface area of β-dicalcium silicate decreased with temperature. The hydration studies were done by determining the nonevaporable water, calcium hydroxide (CH) contents, and specific surface area of the hydrated samples. X-ray diffraction studies were also done. The results showed that prepared β-dicalcium silicate is highly reactive. Calcium chloride (1.0 wt%) and gypsum retard the hydration. Possible causes of high reactivity have been discussed.     

Highly transparent flexible polydimethylsiloxane films – a promising candidate for optoelectronic devices

In the present work, a siloxane based flexible substrate for optoelectronic applications with improved flexibility and high temperature withstanding capacity has been fabricated and the details are reported. The structural and optical properties of the substrate were characterized and the optical transparency is found to be about 90% ? 95% in the visible region. The substrate withstands temperatures up to 300 °C without significant degradation and has a low thermal coefficient of expansion. Fourier transform infrared spectral data show the materials in the prepared substrate and SEM studies show the surface and cross‐sectional characteristics of the substrate. It has good mechanical strength, can withstand a high breaking load of 7 N, has a average tensile strength of 48.86 MPa and high average tensile modulus of 127.32 and also possesses excellent surface smoothness and resistance to both chemical and moisture with better rigidity; it will be a long lasting alternative for flexible plastic substrates. The optical characteristics such as refractive index (n) and extinction coefficient (k) are also reported. © 2016 Society of Chemical Industry     

Inferential Control of Reactive Destillation Columns – An Algorithmic Approach

Decentralized control system design comprises the selection of a suitable control structure and controller parameters. Here, mixed integer optimization is used to determine the optimal control structure and the optimal controller parameters simultaneously. The process dynamics is included explicitly into the constraints using a rigorous nonlinear dynamic process model. Depending on the objective function, which is used for the evaluation of competing control systems, two different formulations are proposed which lead to mixed‐integer dynamic optimization (MIDO) problems. A MIDO solution strategy based on the sequential approach is adopted in the present paper. Here, the MIDO problem is decomposed into a series of nonlinear programming (NLP) subproblems (dynamic optimization) where the binary variables are fixed, and mixed‐integer linear programming (MILP) master problems which determine a new binary configuration for the next NLP subproblem. The proposed methodology is applied to inferential control of reactive distillation columns as a challenging benchmark problem for chemical process control.     

Reactive Hot Pressing and Properties of Zr1−xTixB2–ZrC Composites

Reactive hot pressing was used to prepare Zr_1?xTi_xB₂–ZrC composites with advantageous microstructure and mechanical properties from ZrB₂–TiC powders. The reaction mechanisms and the effects of different levels of TiC on the physical and mechanical properties of the resulting composite were explored in detail and compared to conventionally hot‐pressed ZrB₂ and ZrB₂–ZrC. Incorporation of 10 to 30 vol% TiC enabled full densification and restrained grain growth, reducing the final average grain size from 5.6 μm in pure ZrB₂ to a minimum of 1.4 μm in samples with 30 vol% TiC. The flexural strengths and hardnesses of the composites sintered with TiC were consequently greater than the conventionally processed ZrB₂–ZrC materials, increasing from 440 MPa and 17.4 GPa to a maximum of 670 MPa and 24.2 GPa at 10 vol% TiC. However, despite a decrease in the total average grain size, the flexural strength at higher TiC levels was limited by an increase in ZrC grain growth, which was observed to determine the flexural strength of the reaction sintered composites similar to the case of ZrB₂–SiC.     

New Intermediates and Dyes for Synthetic–polymer Fibres 4–(4–Methoxyanilino)–3–nitro–l, 8–naphthalimides

The synthesis of a series of 4–(4–methoxyanilinoj–3–nitro–1, 8–naphthalimides by condensation of amines with 4–(4–methoxyanilino)–3–nitronaphthalene–l, 8–dicarboxylic anhydride, and also by condensation of 4–halogeno–3–nitro–1, 8–naphthalimides with 4–methoxyaniline is described. They dye synthetic–polymer fibres, particularly polyesters, deep orange of excellent fastness properties. In presence of strong bases, e. g. 3–aminopropan–l–ol, the 4–arylamino group is replaced, giving a series of yellow dyes. A method is described for preparing the dyes without isolation of intermediate stages.     

Synthesis and Highly Stereoselective Hydrogenation of the Statin Precursor Ethyl (5S)‐5,6‐Isopropylidenedioxy‐3‐oxohexanoate

A search for the large‐scale preparation of (5S)‐5,6‐(isopropylidenedioxy)‐3‐oxohexanoates ( 2 ) – a key intermediate in the synthesis of pharmacologially important statins – starting from (S)‐malic acid is described. The synthesis of the required initial compound methyl (3S)‐3,4‐(isopropylidenedioxy)butanoate ( 1 ) by Moriwake’s reduction of dimethyl (S)‐malate ( 3 ) has been improved. Direct 2‐C chain elongation of ester 1 using the lithium enolate of tert‐butyl acetate has been shown to be successful at a 3‐ to 5‐fold excess of the enolate. Unfortunately, the product, tert‐butyl (5S)‐5,6‐(isopropylidenedioxy)‐3‐oxohexanoate ( 2a ) is unstable during distillation. Ethyl (5S)‐5,6‐(isopropylidenedioxy)‐3‐oxohexanoate ( 2b ) was prepared alternatively on a multigram scale from (3S)‐3,4‐(isopropylidenedioxy)butanoic acid ( 7 ) by activation with N,N′‐carbonyldiimidazole and subsequent reaction with Mg(OOCCH₂COOEt)₂. A convenient pathway for the in situ preparation of the latter is also described. Ethyl ester ( 2b ) can be advantageously purified by distillation. The stereochemistry of the catalytic hydrogenation of β‐keto ester ( 2b ) to ethyl (5S)‐5,6‐(isopropylidenedioxy)‐3‐hydrohyhexanoate (syn‐ 6 and anti‐ 6 ) has been studied using a number of homogeneous achiral and chiral Rh(I) and Ru(II) complexes with phosphine ligands. A comparison of Rh(I) and Ru(II) catalysts with (S)‐ and (R)‐BINAP as chiral ligands revealed opposite activity in dependence on the polarity of the solvent. No influence of the chiral backbone of substrate 2b on the enantioselectivity was noted. A ratio of syn‐ 6 /anti‐ 6 =2.3 was observed with an achiral (Ph₃P)₃RuCl₂ catalyst. Ru[(R)‐Tol‐BINAP]Cl₂ neutralized with one equivalent of AcONa afforded the most efficient catalytic system for the production of optically pure syn‐(5S)‐5,6‐isopropylidenedioxy‐3‐hydroxyhexanoate (syn‐ 6 ) at a preparative substrate/catalyst ratio of 1000:1.     

Highly Stereoselective Synthesis of Arylene‐Silylene‐Vinylene Polymers

Stereoregular trans‐arylene‐silylene‐vinylene polymers of M_w=13100–34800 and PDI=1.6–2.9 of the general formulas CH₂CH [ SiMe₂C₆H₄‐SiMe₂CHCH ] ( 16, 17, 18 ) and CH₂CH [ (R)CHCHC₆H₄CHCH ] (where R= Me₂Si‐p C₆H₄‐ SiMe₂ ,  Me₂Si‐m C₆H₄SiMe₂ and  Me₂SiC₆H₄C₆H₄SiMe₂ ) ( 19, 20, 21 ) have been effectively synthesized via silylative coupling (SC) homopolycondensation of bis(vinyldimethylsilyl)arenes ( 10, 12, 14 ) and cross‐polycondensation of 4‐(vinyldimethylsilyl)styrene ( 11 ) as well as cross‐copolycondensation of bis(vinyldimethylsilyl)arenes ( 10, 12 and 14 ) with 1,4‐divinylbenzene ( 9 ) catalyzed by [RuH(Cl)(CO)(PCy₃)₂] ( 7 ). Such highly stereoregular products cannot be synthesized via ADMET polycondensation or ring opening metathesis ROM or polyaddition of hydridosilanes to acetylenes.     

Highly Regio‐ and Stereoselective Iodohydroxylation of 1,2‐Allenylic Sulfoxides in the Presence of Benzyl Thiol

The iodohydroxylation of 1,2‐allenyl sulfoxides with iodine in the presence of benzyl thiol afforded 3‐hydroxy‐2‐iodo‐2(E)‐alkenyl sulfides in good yields and high regio‐ and stereoselectivities. In this reaction it was observed that the sulfoxide functionality was reduced to sulfide and the water in the reaction mixture plays an important role for the stereoselectivity observed. A mechanism involving the attack of benzyl thiol at the positively charged sulfur atom in the five‐membered intermediate 2 has been proposed.     

4–Hydroxy–3–arylamino–l, 8–naphthalimides and 3–(and 4–) hydroxy–2–(and 5–) arylamino–7H–bcnzimidazo–(2, l–a)benz(d,e)isoquinolin–7–ones. Red dyes for synthetic–polymer fibres

4–Hydroxy–1, 8–naphthalimides and the isomer mixtures of'3–and 4–hydroxy–7 H–benzimidazo–(2, l–a)–benz(d, e)–isoquinolin–7–ones were coupled with diazotised arylamines to yield orange–red to bluish–red dyes having good coloration properties and excellent fastness to light on polyester fibres. Structure–property relationships in the dyes are discussed with respect to the nature of the substituents in the imide, imidazole and arylazo moieties.     

Highly Reactive Remelted Belite

Remelted belite showed higher hydration activity and better grindability than the quenched material. Both properties were closely related to the belite microtextures induced by the remelting reaction; after the reaction, the belite showed disintegration of the intracrystalline lamella structure, inclusion of the liquid exsolved on the former lamella boundaries, and crystallization of the liquid during further cooling. The fractures easily penetrated the remelted crystal grains upon grinding, probably along the disintegrated lamella boundaries and/or along the inclusions. The resulting fragments were irregular in shape with high specific surface area, leading to the high hydration activity of the remelted belite.     

Mikroverfahrenstechnik: Komponenten – Anlagenkonzeption – Anwenderakzeptanz – Teil 3

Microtechnology: Components – Plant Concepts – User Acceptance Many activities over the last five or so years have focussed on the thus far underdeveloped field of carrying out reactions on small scales. Due to the rapid development of new components, this paper touches on recent developments only in a compressed form. An important point is the analysis of possible plant concepts for microreactors and whether these are a sensible option. Due to the enormous size difference between the microchannels and the fluid periphery of possible components this is not just a technical question, it touches on the microtechnology concept as a whole. The direction in which the field should be developed and which measures can be taken to influence its development, are questions that are addressed here with respect to the big industrial interest in microreactors.     

Identification of Newer Types of Reactive Dyes on Cellulosic Fibres – IV

The reactive systems and chromogens present in further types of reactive dye are briefly discussed. Dyeings, or prints, on cotton of selected dyes in each range, including more black reactive dyes, have been tested to distinguish between the various types of reactive dye. Special attention is paid to methods of detecting the presence of metals in reactive dyeings.