Copolymers from α-Pinene. 2. Cationic Copolymerization of Styrene and α-Pinene

A study of the copolymerization of α-pinene and styrene has been carried out at 10°C using anhydrous AlCl₃ as the initiator. It is found that styrene forms copolymer with α-pinene at all mono-meric ratios. A copolymer of 2320–3080 molecular weight is obtained. The softening range of the copolymer is 82 to 85°C. The copolymers are of commercial value.     

Synthesis of Terpenoids. III. Total Syntheses of α-Bisabololone and α-Trans-Atlantone

Recently, anions of “protected” cyanohydrins have been introduced as useful acyl carbanions equivalents in organic synthesis². Continuing with our interest in the use of these reagents for natural product syntheses³, we wish to report a short total synthesis of the sesquiterpene α-bisabololone 1 ^4,5, whose salient feature is a novel application of “protected” cyanohydrins to the synthesis of β-hydroxy ketones.     

Derivatives of heterocyclic α-iminocarboxylic acids. 4. Reduction of N-alkoxycarbonyl derivatives of α-iminocarboxylic acids

When N-methoxycarbonyl and N-benzoxycarbonyl derivatives of methyl esters of aziridine-2-carboxylic acid, L-proline, L-thioproline, and pipecolic acid interact with NaBH₄ in tert-butanol/methanol, the products of reduction of the C-methoxycarbonyl group of the original compounds are accompanied by bicyclic urethanes and oxazolidines. Reduction of N-maleates and N-fumarates of heterocyclic -iminocarboxylic acids leads to the formation of -hydroxymethyl-N-[4-(2-oxo-2,5-dihydrofuryl)] derivatives of pyrrolidine, piperidine, 1,3-thiazolidine, and 1,4-thiazan. In the latter case, 1-aza-2-hydroxymethyl-4-oxo-5-oxa-9-thiabicyclo [5.4.0]undecene-2 is also obtained. The N-maleates and fumarates of aziridine-2-carboxylic acid are reduced anomalously by sodium borohydride, forming 2-hydroxymethyl-2-(-hydroxyethyl)-3-oxa-1-azabicyclo[3.1.0]hexanes.For Communication 3 see [2].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1567–1573, November, 1993.     

Spirophosphoranes D′ α-Cetoacides. Structure Cristalline. Induction Asymetrique

Des couples d'énantiomères diastéréoisomères de spirophosphoranes ont été préparés en faisant réagir le trichlorophosphane sur l'acide céto-2-glutarique. Par cristallisation sélective, un couple a été isolé dont la structure a été déterminée par diffraction des rayons X. Les sels de triéthylammonium de thiolo et sélénospirophosphoranes ont été obtenus en faisant réagir le soufre ou (et) le sélénium sur les spirophosphoranes préparés à partir des acides phénylpyruvique et céto-2-glutarique. Tous ces résultats ont été rationalisés par des calculs semi-empiriques.     

Oxime derivatives as α-electrophiles. from α-tetralone oximes to tetracyclic frameworks

When subjected to the conditions of a Semmler-Wolff/Schroeter aromatization, the oximes of 4-benzyl-substituted tetralones undergo an electrophilic aromatic substitution reaction to form tetracyclic frameworks.     

Reaction of nitroalkanes with levoglucosenone and its α-bromo and α-iodo derivatives. Cyclopentaannulation of α-halocyclenones

Michael reactions of levoglucosenone and its α-bromo and α-iodo derivatives with α,ω-dinitroalkanes were studied under conditions of chemical and electrochemical generation of base. Procedures were developed for stereospecific fusion of a cyclopentane ring to α-bromo- and α-iodolevoglucosenones, 2-iodocyclopent-2-en-1-one, and 2-iodocyclohex-2-en-1-one by the action of 2,2-dimethyl-1,3-dinitropropane.     

Fungizide Pyridinderivate, 4. Mitt.: α-Trifluormethyl-3-pyridinmethanole

Summary The synthesis of a series of the title compounds is described applying the addition of 3-pyridyllithium to appropriate trifluoromethylalkanones (path 1) and addition of lithiumorganyls to 2,2,2-trifluoro-1-(3-pyridyl)-ethanone (path 2), respectively.

     

Synthesis with organoboranes. 21. Synthesis of α- and gd-bamascone

Selective syntheses of α- and gd-damascone, using allylic organoboranes as the key intermediates, are described.     

1,3-Diphenylpropan-1,3-diamines IX. reaction of α-chlorooxime ethers with α-lithiobenzylamines

Summary The carbanions of the benzylamine derivatives1–4 have been reacted with -chlorooxime ether5 in order to get precursors of 1,3-diphenylpropane-1,3-diamines. Isonitrile1 afforded the expected result, whereas lithiated benzamide2 underwent oxidative dimerization and transmetallated chlorooxime derivative5. Isoxazolidine3 gave the condensation product21 as a mixture of diastereomers; treatment of imine4 led to the desired amine-oxime15 in low yield.Dedicated with warm regards to Prof. Dr.J. Knabe, Saarbrücken, Germany, on the occasion of his 75^th birthday     

Quasiliving Carbocationic Polymerization. II. The Discovery: The α-Methylstyrene System

A detailed analysis of elementary reactions of carbocationic polymerization culminated in the prediction and subsequent experimental demonstration of quasiliving polymerization. Quasiliving polymers are formed in a system provided that the process of chain termination and chain transfer to monomer are absent or reversible, i.e., the propagating ability of the chain end is maintained throughout the experiment, and the molecular weight increases in proportion to the cumulative amount of monomer added. The chain end can be active (carbocation) or dormant (reactivable polymeric olefin or cation source). Chain transfer is suppressed by keeping the monomer concentration low. Quasiliving polymerizations are maintained by continuous slow feeding of dilute monomer to a charge containing the initiating or propagating species (quasiliving polymerization technique). A comprehensive kinetic scheme has been developed that describes quasiliving polymerization in quantitative terms. Quasiliving polymerization was demonstrated experimentally in the “H₂O”/BCl₃/α-methylstyrene and cumyl chloride/BCl₃/α-methylstyrene systems. M _n versus monomer input plots are linear over wide ranges, indicating quasiliving conditions, and poly(α-methylstyrenes) with M _n > 2 × 10⁵ have been obtained, Molecular weight distributions were found progressively to narrow and dispersion ratios M _w/M _n to decrease.     

Anionic Polymerization of α-Methylstyrene. IX. Nature of the Propagating Species

Abstract

The nature of the initiating and propagating species involved in the anionic polymerization of α-methylstyrene has been explored. The earlier hypothesis that multimodal GPC molecular weight distributions in polymers arise solely out of different reaction steps or different ion-pair mechanisms being involved has been modified for poly-α-methylstyrene. Multimodal GPC molecular weight distributions in poly-α-methylstyrene initiated with potassium at 25°C and polymerized at 25°C or higher in THF, p-dioxane, or cyclohexane as solvents have been ascribed to the presence of two different types of tetramers which grow simultaneously but at different rates, each responding to its own well-defined thermodynamic equilibrium and yielding dormant and living polymers. Reaction schemes describing the initiation (at 25°C) and propagation reactions (between -25 and 60°C) in the polymerization (in solution of THF as well as in bulk) of α-methylstyrene initiated with potassium-naphthalene, butyl-lithium, and butyllithium-tetramethylethylenediamine (TMEDA) have been presented. The role of coordinating agents naphthalene and TMEDA in changing irreversible propagations into reversible ones has been emphasized.     

Free-Radical Copolymerization of Methyl Methacrylate and α-Methacrylophenone. I. Reactivity Ratios

The free-radical copolymerization of methyl methacrylate and methacrylophenone (MAP) initiated by azobisisobutyroni-trile at 60°C has been studied in ethylbenzene solution and in bulk. The process is characterized by a competitive Diels-Alder condensation of methacrylophenone and by a very low reactivity of methacrylophenone-terminated macroradicals in propagation reactions. The experimental composition data are consistent with a terminal unit model: r_A = 1.77 ± 0.02, r_B = 0.110 ± 0.006. Copolymerization with depropagation of methacrylophenone-terminated growing chains and copolymerization affected by penultimate effects have been tested as optimized possible models to take into account the inability of MAP to undergo homopolymerization.     

Kondensationen mit halogenierten Aldehyden. Mitt. X: α-Thienylrhodanid und Chloral

Zusammenfassung Durch Abbau- und Syntheseversuche wird ermittelt, daß -Thienylrhodanid (I) und Chloral in Gegenwart von konz. Schwefelsäure unter Bildung von N, N-[,,-Trichlor-äthyliden]-bis-[thienyl-(2)-mercaptan-S-carbonsäureamid] (IV) miteinander reagieren.Mitt. IX; J. Amer. Chem. Soc.74 (im Druck seit 12. 1. 1953); Mitt. VIII: Mh. Chem.84 (im Druck. seit 26. 11. 1952).– b) Mitt. II: Pharmazie4, 460 (1949).– c) Mitt. V: Z. Naturforsch.7 b, 277 (1952).     

Desilylation of α-trimethylsilylmethylene-δ-lactones. A new route to α-methylene-δ-lactones

Addition of phenylthiol to α-trimethylsilylmethylene-δ-lactones affords α-phenylthi(trimethylsilyl)methyl-δ-lactones which, on treatment with tetrabutyl-ammonium fluoride and methyl acrylate give the corresponding α-methylene-δ-lactones through a one-pot double deblocking process.     

Fungizide Pyridinderivate, 2. Mitt.: Derivatisierung von α-Trichlormethyl-3-pyridinmethanol

Summary The antifungal lead structure -trichloromethyl-3-pyridinemethanol (1 a) was modified and esters, (thio-)carbamates, and sulfonates as well as other derivatives incorporating the pyridylcarbinol structure were prepared. The optical resolution as well as the N-oxidation of1 a are described.