Christo Ivanov

Optical plastic refractive measurements in the visible and the near-infrared regions

Some new refractometric results are obtained in the visible and the near-infrared spectral regions. The main optical plastics are analyzed: poly(methyl methacrylate), polystyrene, polycarbonate, and styrene acrylonitrile. New materials, such as methyl methacrylate styrene copolmer, CTE-Richardson, Zeonex, Optorez, and Bayer are examined. The refractive indices are measured for wavelengths from 435.8 to 1052 nm with a new device. Abbe constants and dispersion coefficients are calculated. The measured and computed data is intended for designers and technologists.

A comparative study of the interaction of salicylaldehydes with phosphonoacetates under Knoevenagel reaction conditions. Synthesis of 1,2-benzoxaphosphorines and their dimers

Abstract The reaction of salicylaldehydes 5 with phosphonoacetates 6 gives the coumarin-3-phosphonates 7 and the 1,2-benzoxaphosphorine-3-carboxylates 8 in yields and 7:8 ratios depending on the reaction conditions. A mechanistic explanation is given for the stereoselectivity of these reactions. Irradiation of compounds 8 or direct exposure to sunlight causes their head-to-tail dimerization, giving the dimers 11 and in one case its phosphorous epimer 12 . Their structure was confirmed by x-ray crystallographic analyses. Some spectroscopic characteristics of diagnostic importance for compounds 7, 8, 11 and 12 are also discussed.

Measuring the refractometric characteristics of optical plastics

Ten types of American, Japanese, and German optical plastic (OP) materials are examined. The principal OPs are analysed: polymethyl methacrylate, polystyrene, polycarbonate, and styrene acrylonitrile. Refractive indices are measured and calculated for the principal and some new applicable OPs, namely NAS-21 Novacor, CTE-Richardson, Zeonex E48R, Optorez 1330 and Bayer for wavelengths from 435.8 to 1052 nm. A theoretical examination was made for computer modelling of OPs indices using Cauchys dispersion formula. The dispersion coefficients and Abbe constants are calculated. The OPs indices computed for numerous laser wavelengths 442–1060 nm are presented. A more effective device and technology for the measurement of refractive index of OPs is realized with an accuracy of ±0.001.

Cyclopropanation reaction of 3-acyl-2H-1-benzopyran-2-ones with phenacylbromide in phase transfer systems

Abstract 3-Acyl-2 H -1-benzopyran-2-ones 1 reacted wih phenacylbromide in the presence of a base to give the cyclopropane derivatives 2 and 3 in moderate yields. The yields of the reaction products were substantially improved by using a catalyst (Aliquat 336 or TPBP) under phase-transfer conditions. A mechanistic explanation is given for the stereoselectivity of these reactions. Spectroscopic data for compounds 2 and 3 are also given.

Reactions of calcium and magnesium naphtalenides with ethyl esters of 2-bromopropionic and 2-bromobutyric acid in liquid ammonia

Abstract The reaction in liquid ammonia of magnesium naphtalenide with the ethyl esters of 2-bromoproionic and 2-bromobutyric acid gives after hydrolysis the corresponding 2,2′ -dialkylsuccinic acids, whereas calcium naphthalenide reacts to give in the former case 2,2′ -dimethyl anhydride, and 2-hexene-3,4-dicarboxylic acid in the latter. Possible reaction mechanisms are discussed.

Über die Reaktion von Biphenyl mit Magnesium in flüssigem Ammoniak

The interaction between magnesium and biphenyl in liquid ammonia has been studied. It was shown that the metal adduct formed reacts slowly with the reaction medium to give tetrahydroderivatives of biphenyl.A comparative study was carried out in order to reveal the influence of the metal used on the reaction pathway. It was found that the nature of the reaction products markedly differs when lithium, sodium or magnesium were used in the reaction.Possible reaction mechanisms are discussed.

Potassium Fluoride Promoted Reaction of 3-Acylsubsti-Tuted 2H-1-Benzopyran-2-Ones with Acid Anhydrides. An Improved Method for the Synthesis of 4-(2-Oxoalkyl)-2H-Chroman-2-Ones. Part III1

Abstract The reaction of 3-acylsubstituted 2H-1-benzo-pyran-2-ones 1, 5 and 11a-c with acid anhydrides in the presence of potassium fluoride (KF)/molecular sieves 4A gives the 4-(2-oxoalkyl)-2-oxochromans 2, 6 and 12a-c as the main products. Also the 3-carboxylic acid derivatives, such as esters and N,N-dialkylamides, of 2H-1-benzopyran-2-one (11d-g) react with isobutyric acid anhydride in the presence of KF/molecular sieves 4A to give the corresponding 2-oxochroman-4-acetic acid derivatives.

REGIO- AND STEREO-SELECTIVE 1,3-DIPOLAR CYCLOADDITION REACTIONS OF ETHYL DIAZOACETATE TO 3-SUBSTITUTED 2H-1-BENZOPYRAN-2-ONES

Abstract The cycloaddition of ethyl diazoacetate to 3-substituted 2H-1-benzopyran-2-ones, 1, gave the benzopyranol[3,4][2]pyrazolines 11, the benzopyrano[3.4]cyclopropanes 12, the benzopyrano[3,4-c]pyrazole 13 and the (o-hydroxy)phenyl-pyrazoles 14 as the main products. When the cycloaddition was performed in the presence of silica gel the rate of the reaction increased substantially and the yields of the cyclopropane derivatives 12 were more than doubled. Ethyl diazoacetate adds to benzopyran-3,4-double bond regio- and stereo-selectively giving the endo-form of the initial cycloadduct 15, which being unstable, is then transformed mainly to the above mentioned compounds.

Interaction of Nitromethane with Esters and Amides of 2-Oxo-2H-1-benzopyrane-3-carboxylic Acid

Abstract The reaction of esters as well as N,N-disubstituted amides of 2-oxo = 2H-1-benzopyran-3-carboxylic acid with nitromethane in the presence of potassium fluoride leads to the corresponding diesters and ester -amides of 2-carboxy-3-(2-hydroxyphenyl)-4-ni trobutyric acid (2a-m). The configuration and preferable conformation of the ester-amides are discussed.

Influence of ultraviolet light on some copper chelates of β-dicarbonyl compounds : Spectral evidence for a photoactivated metallotropy

Abstract The influence of ultraviolet light on heptane solutions of the copper chelates of several β-dicarbonyl compounds has been followed by spectroscopy. Reversible transformations are apparent, leading us to assume the presence of a photoactivated metalotropy.