Some new aspects on the chemistry of 1,4-benzoxazines

3-Methyl ( 3a ) and 3-t-butyl-1,4-2H-benzoxazine ( 3b ) were synthesized by cyclization of the appropriate acetamidoketone (Scheme 1). The former is a highly unstable molecule which rapidly converts in an intractable mixture, while the latter slowly undergoes aerial oxidation affording the hemiacetal 4. The 4H-forms of the same 3-methyl ( 6a ) and of the parent 1,4-benzoxazine ( 9 ) could be obtained as 4-acetyl derivatives. This latter, by hydrolysis, gave the cyclic trimer 10.     

Some aspects of reduced quinoline chemistry

Different synthetic paths that produce the reduced quinoline cycle are discussed: among them intramolecular cyclization, intra- and inter [4+2] cycloaddition reactions and other methods. Some chemical properties of tetrahydroquinolines are also analyzed.     

Some aspects of organosilicon and ferrocene chemistry

This review deals with three topics selected from my researches carried out over a period of nearly 40 years up to my retirement in 1983, namely (1) methylpolysilane chemistry, (2) some chemical properties of ferrocene-substituted silicon compounds and (3) some organic syntheses catalyzed by ferrocenylphosphine-transition metal complexes.     

Some aspects of fluorine chemistry in Göttingen

The review gives a short summary of some developments in fluorine chemistry in Göttingen. A major part covers sulphur-nitrogen-fluorine compounds and their derivatives. Furthermore the chemistry of organometallic fluorides of main group and transition elements is described. Fluorine containing compounds of group 4 and group 13 are good candidates for catalysis and material science.     

Studies in the heterocyclic series. XIX. Synthesis of 1,4-diazaphenothiazine and its benzo derivatives

1,4-Diazaphenothiazine, the parent compound of this heterocyclic ring has now been prepared from 2,3-dichloropyrazine and 2-aminothiophenol. Replacement of 2,3-dichloropyrazine with 2,3-dichloroquinoxaline and 2,3,6-trichloroquinoxaline led to the corresponding 1,4-diazabenzo[b]phenothiazine in good yields. Structural assignments were made by spectroscopic studies and by certain chemical transformations.     

Some aspects of the chemistry of chlorofluoro-olefins which contain allylic chlorine atoms

Routes to perflouroallyl chloride, CF₂:CF.CF₂Cl, and to $\text{cis}$-and $\text{trans}$-1-chloro-hexafluoro-2-trifluoromethyl(but-2-ene), (CF₂Cl)(CF₃)C:CF.CF₃ are reported, and their susceptibility to attack by nucleophiles discussed; the allylic chlorine atoms in these olefins are the controlling factor in determining the products obtained.The conversion of 3-chloropentafluoropropene into a series of perfluoroallyl derivatives of general formula R.CF₂.CF:CF₂ [R = (CF₃)₃C-, CF₃O-, C₆F₅-, l-, MeO-, etc.] is described, and the further chemistry of 3-chloropentafluoropropene and its derivatives outlined.Water reacts rapidly with (CF₂Cl)(CF₃)C:CF.CF₃ to give CF₂:C(CF₃).CFCl.CF₃ or CF₃.CO.CH₂.CF₃. Methanol affords CF₂:C(CF₃).CFOMe.CF₃ and (MeOCF₂)(CF₃)C:CF.CF₃ as initial products, with subsequent secondary products such as CF₃.CFOMe.CH(CF₃).CF₂OMe, (CF₃)(MeO)C:C(CF₃).CF₃OMe, MeO.CF:C(CF₃).CFOMe.CF₃, (CF₃)(MeO)CF.CH(CF₃).CO₂Me, and (CF₃)(MeO)C:C(CF₃).CO₂Me. The influence of allylic chlorine and of reaction time on the formation of these products, and mechanistic pathways for their formation are considered.     

Some aspects of the chemistry of pyrimido[1,2-B]pyridazinones

On reacting the 3-aminopyridazines 1a,d,e with dimethyl acetylenedicarboxylate (DMAD), the pyrimido[1,2-b]pyridazin-2-(2H)-ones 2e-g , whereas starting from 1f , the 4(4H)-ones 5a and 3b,d were prepared. In the 2(2H)-one series, the reactions of 2b with various amino compounds resulted in various types of products. The reaction of N-methylaminopyridazines 1g,h with DMAD led to the endo-N-substituted derivatives 8a,b , whereas 1h with diethyl ethoxymethylenemalonate (DEM) gave the exo-N-substituted compound 1k. The constitution of the compounds was proved by spectroscopic and chemical evidences.     

Kinetic aspects of analytical chemistry

A broad view of the role of kinetics in analytical chemistry is presented. Two principal themes are that the role of kinetic methods is much greater than is generally acknowledged and that the most commonly used kinetic approaches make inadequate use of information that is available. After a brief discussion of historical developments that date back to the latter part of the 1800s, primary attention is focused on a classification of measurement and data-processing approaches that have been developed. Approaches are grouped into methods for single components without and with error compensation and methods for resolving two or more components in mixtures. They are further grouped into direct-computation and curve-fitting approaches and into integral and derivative methods within these more general categories. Correlations are then drawn between these approaches as applied to chemical processes and to physicochemical and purely physical processes such as luminescence, electrode responses, and flow systems, including chromatographic processes. It is argued that all analytical methods are either kinetic or equilibrium in character and that kinetic-based methods represent a much larger fraction of the total than is generally recognized.     

Dynamic aspects of quantum chemistry

Some contributions of quantum chemistry to the field of atomic dynamics are reviewed and it is argued that, in return, the area of application of quantum chemistry has become considerably extended and has given rise to insight into processes closely related to bond formation.     

Oxidation of thiolesters : Some aspects of the chemistry of s-acylthiol s-oxides and related compounds

In the ozone oxidation of thiolesters in 1,2-dichloroethane at room temperature, S-acylthiol S-oxides 3 are proposed as intermediates. The isolation of carboxylic acid anhydrides and dialkyl disulphides as the actual reaction products can be explained as resulting from the decomposition of the unstable. S-acyl S-acyloxysul-phonium salt 4 arising probably from the reaction of the intermediate S-acylthiol S-oxides with another mole of thiolester. However, in the case of hindered thiolesters, the S-acylthiol S-oxides formed rearrange, possibly via an S→ O acyl shift, to the corresponding acyl sulphenates 12 which on further oxidation lead to the mixed carboxylic acid sulphonic acid anhydrides 13.     

Philosophical aspects on analytical chemistry

Summary This contribution is neither a cosmetic facelifting of an old but loved and admired lady nor is it an advertisement for Selling new lamps for old. It is simply a trial to clarify the actual situation and position of analytical chemistry and its paradigmatic change to analytics and its general role in our building of knowledge of nature. Taken this essay in this sense, it is a contribution to the most relevant question: how do we study the nature and what is the validity of knowledge.

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Philosophische Betrachtungen zur Analytik