Thermodynamic properties of oxygen compounds II. β-propiolactone, γ-butyrolactone,and γ-butyrolactam (2-pyrrolidone)

A complete vibrational assignment is made and ideal gas thermodynamic properties are reported for β-propiolactone, γ-butyrolactone and γ-butyrolactam over the range 100–1500 K.     

Polymerization of optically active β-substituted β-propiolactones. IV. β-1,1-dichloroalkyl β-propiolactones polymerized with aluminum triisopropoxide

The polymerization of three optically active β-1,1-dichloroalkyl β-propiolactones has been investigated in toluene, at 55°C, using aluminum triisopropoxide (Al(OiPr)₃) as initiator in a range of monomer/initiator molar ratios smaller than 150. β-1,1-dichloroethyl β-propiolactone polymerizes according to a living mechanism. However, the ability to polymerize decreases with an increase in the length of the alkyl substituent. For instance, β-1,1-dichloro-n-propyl β-propiolactone is obtained only in low yields, whereas β-1,1-dichloro-n-butyl β-propiolactone does not polymerize at all. Actually, each of the lactones investigated reacts with Al(OiPr)₃ in an initiation step that obeys a coordination-insertion mechanism. However, the size of the chloroalkyl substituent has a critical effect on the propagation: when the alkyl group contains more than two methylene units, the insertion of a second monomer becomes exceedingly slow.     

A New Type of Photorearrangement of γ-Hydroxy-α, β, δ, ε-dienone

A new type of photorearrangement of the γ-hydroxy-α, β, δ, ε-dienone, vomifoliol acetate ( 2 ) to the diketone 4 is described, and its facile rearrangement is compared with that of desoxyvomifoliol acetate ( 3 ).     

Substituent effect in anionic polymerization of β-lactones initiated by alkali metal alkoxides

The influence of methyl substituent on the mechanism of the ring-opening polymerization of β-lactones initiated by alkali metal alkoxides is discussed. Attention has been paid to the effect of the substituent position in the monomer molecule on the ring-opening mechanism, the 3,3-dimethyl-2-oxetanone (pivalolactone), 4-methyl-2-oxetanone (β-butyrolactone) and 2-oxetanone (β-propiolactone) being chosen as model monomers. Moreover, it was found unexpectedly that in the case of pivalolactone polymerization, besides open-chain polymers, cyclic oligomers are produced.     

Synthesis and polymerization of racemic and optically active β-substituted β-propiolactones. III. β-monosubstituted monomers and polymers

Optically active β-(1,1-dichloroethyl)-β-propiolactone (CH₃CCl₂-PL), β-(1,1-dichloropropyl)-β-propiolactone (C₂H₅CCl₂-PL), and β-(1,1-dichlorobutyl)-β-propiolactone (C₃H₇CCl₂-PL) were synthesized with enantiomeric excesses of 100, 100, and 84%, respectively. Polymerization was conducted in bulk and toluene solution, under vacuum, using mainly ZnEt₂/H₂O as initiator. Osmometry analyses indicate molecular weights in the range 10,000–25,000. The polymers thus prepared are semi-crystalline and show large optical rotation values.¹³ C-NMR was used to show that they have a high degree of isotacticity, indicating that little or no racemization occurs in the course of polymerization. Glass transition, melting and decomposition temperatures are given as a function of the size of the substituent, and their variations are discussed.     

Synthesis and polymerization of racemic and optically active substituted β-propiolactones. VI. α-Phenyl β-propiolactone

The synthesis and optical resolution of α-phenyl β-amino-ethylpropionate led to the preparation of optically active α-phenyl β-propiolactones (PhPL) of different optical purities. The enantiomeric excess of PhPL was determined using 200 MHz ¹H-NMR spectroscopy, after complexation with tris[3-(trifluoromethyl hydroxymethylene)-d-camphorato]europium III. It was then polymerized, in bulk and in solution, using a potassium acetate/crown ether complex as initiator. The optically active poly(PhPL)s thus obtained are insoluble in most organic solvents, whereas atactic poly(PhPL)s are soluble in CCl₄, CHCl₃, and dichloroethane. Several differences are observed between the physical properties of optically active and atactic poly(PhPL)s. However, atactic poly(PhPL)s are semi-crystalline polymers, similar to poly(α-disubstituted β-propiolactone)s, but in contrast with poly(α-methyl β-propiolactone). Melting (T_f) and glass transition temperatures, as well as enthalpy of fusion (ΔH), vary with the optical purity of the polymers. For example, atactic poly(PhPL) exhibits a T_f = 94°C and ΔH = 9 J/g as compared to T_f = 119°C and ΔH = 37 J/g for a poly(PhPL) having an enatiomeric excess of 50%.     

Synthesis and polymerization of racemic and optically active β-substituted β-propiolactones. II: β-monosubstituted and β-disubstituted monomers and polymers with different optical purities

β-(trichloromethyl)-β-propiolactone (CCl₃-PL), β-(trifluoromethyl,methyl)-β-propiolactone (CF₃, Me-PL) and β-(trifluoromethyl,ethyl)-β-propiolactone (CF₃,Et-PL) have been obtained by the reaction of ketene with chloral, 1,1,1-trifluoroacetone and 1,1,1-trifluorobutanone, respectively. Chiral catalysis lead to optically active monomers. The enantiomeric excess of the lactones has been measured by ¹H-NMR spectroscopy, in the presence of 2,2,2-trifluoro-1-(9-anthryl)ethanol or an europium chiral shift reagent. Polymerizations have been carried out in bulk or in toluene, at 60°C or 80°C, using mainly organometallic initiators. The Polymers become insoluble and crystalline at enantiomeric excesses over 80% for CCl₃-PL and 70% for CF₃,Me-PL. Melting temperatures were recorded from 238 to 268°C for poly(CCl₃-PL) and from 78 to 100°C for poly(CF₃,Me-PL), depending upon the molecular weight and the enantiomeric excess. The ¹³C-NMR specroscopy of poly(CCL₃-PL) indicates that the polymerization of the corresponding lactone leads to polymers of increasing degrees of isotacticity with the enantiomeric excess of the monomer.     

Die Kristallstrukturen von Me3SiI · β-Picolin und Me3SiI · γ-Picolin Vergleich der Lewis-Basen Pyridin, β-Picolin und γ-Picolin

The Crystal Structure of Me₃SiI · β-Picoline and Me₃SiI · γ-Picoline A Comparison between the Lewis-Bases Pyridine, β-Picoline, and γ-Picoline The reaction of Iodinetrimethylsilane with β- und γ-Picoline (Pic) leads to solid 1 : 1 compounds Me₃SiI · β-Picoline 1 , Me₃SiI · γ-Picoline 2. The reaction was performed at room temperature. Yellow single crystals were obtained by sublimation. Single crystal X-ray investigations confirm that both compounds are ionic [Me₃SiPic]⁺I^?. The comparison of β-Picoline with γ-Picoline and Pyridine (Py) demonstrates that the presence of a methyl group and also its position has no significant influence on the Si? N bond length in compound 1, 2 and on the adduct Me₃SiI · Py.     

γ-Ray-induced copolymerization of carbon monoxide with cyclic ethers

The γ-ray copolymerization of carbon monoxide with cyclic ethers, such as ethylene oxide, phenyl glycidyl ether, 1,3-dioxolane, 2-vinyl-1,3-dioxolane, terahydrofuran, 1,4-dioxane, and acetaldehyde was studied. A yellowish or brownish powdery copolymer was obtained in most of the cases examined. The infrared spectra showed that copolymers containing the ester structural unit were produced in the copolymerization with cyclic ethers which have no vinyl groups, and that a copolymer containing a ketone structure was produced from cyclic ether having vinyl group. It was found that the copolymer with ethylene oxide also had a β-propiolactone ring structure at the chain end or the side chain. The copolymers were confirmed to be partially crystalline from the x-ray diffraction diagrams. Further, a ring-opening polymerizability of the cyclic ether by γ-radiation was discussed. And it was found that as the bond dissociation energy between the carbon–oxygen linkage of the cyclic ether is small, the polymer yield both in the homopolymerization and copolymerization with carbon monoxide is high. A mechanism for the copolymerization is proposed on the basis of the results.     

Thermische Lactonisierung von Estern γ-Brom-α, β-ungesättigter Carbonsäuren zu Δα-Butenoliden. Direkte γ-Bromierung von α, β-ungesättigten Säuren

By heating with iron powder at 120–150° some γ-bromo-α, β-unsaturated carboxylic methyl esters, and, less smothly, the corresponding acids, were lactonized to Δ^7alpha;-butenolides with elimination of methyl bromide. The following conversions have thus been made: methyl γ-bromocrotonate ( 1c ) and the corresponding acid ( 1d ) to Δ^α-butenolide ( 8a ), methyl γ-bromotiglate ( 3c ) and the corresponding acid ( 3d ) to α-methyl-Δ^α-butenolide ( 8b ), a mixture of methyl trans- and cis-γ-bromosenecioate ( 7c and 7e ) and a mixture of the corresponding acids ( 7d and 7f ) to β-methyl-Δ^α-butenolide ( 8c ). The procedure did not work with methyl trans-γ-bromo-Δ^α-pentenoate ( 5c ) nor with its acid ( 5d ). Most of the γ-bromo-α, β-unsaturated carboxylic esters ( 1c, 7c, 7e and 5c ) are available by direct N-bromosuccinimide bromination of the α, β-unsaturated esters 1a, 7a and 5a ; methyl γ-bromotiglate ( 3c ) is obtained from both methyl tiglate ( 3a ) and methyl angelate ( 4a ), but has to be separated from a structural isomer. The γ-bromo-α, β-unsaturated esters are shown by NMR. to have the indicated configurations which are independent of the configuration of the α, β-unsaturated esters used; the bromination always leads to the more stable configuration, usually the one with the bromine-carrying carbon anti to the carboxylic ester group; an exception is methyl γ-bromo-senecioate, for which the two isomers (cis, 7e , and trans, 7d ) have about the same stability. The N-bromosuccinimide bromination of the α,β-unsaturated carboxylic acids 1b , 3b , 4b , 5b and 7b is shown to give results entirely analogous to those with the corresponding esters. In this way γ-bromocrotonic acid ( 1 d ), γ-bromotiglic acid ( 3 d ), trans- and cis-γ-bromosenecioic acid ( 7d and 7f ) as well as trans-γ-bromo-Δ^α-pentenoic acid ( 5d ) have been prepared. Iron powder seems to catalyze the lactonization by facilitating both the elimination of methyl bromide (or, less smoothly, hydrogen bromide) and the rotation about the double bond. α-Methyl-Δ^α-butenolide ( 8b ) was converted to 1-benzyl-( 9a ), 1-cyclohexyl-( 9b ), and 1-(4′-picoly1)-3-methyl-Δ^α-pyrrolin-2-one ( 9 c ) by heating at 180° with benzylamine, cyclohexylamine, and 4-picolylamine. The butenolide 8b showed cytostatic and even cytocidal activity; in preliminary tests, no carcinogenicity was observed. Both 8b and 9c exhibited little toxicity.     

1,6-Asymmetric induction: A higher enantioselective synthesis of γ-butyrolactone

A novel 1,6-asymmetric induction has been observed in the iodolactonization of γ, delta;-unsaturated amides. The optically active γ-butyrolactone was synthesized by employing iodolactonization reaction as a key step.     

Syntheses of stereodefined β-alkylidene-γ-lactones and substituted β, γ-unsaturated δ-lactones

1-Trimethylsilyl-1,3-diyne derived trans-bis(trimethylstannyl) enynes undergo stepwise transmetallation with methyllithium to furnish the corresponding enynyllithium reagents. The application, in various orders, of a sequence of transmetallation-protonation-alkylation-hydroxyalkylation-hydroboration-oxidation reactions provides a novel approach to stereo-defined β-alkylidene γ-lactones and β, γ-unsaturated δ-lactones.     

Polymerization of β-isovalerolactone

The polymerization of β,β′-dimethyl-β-propiolactone with various catalysts was investigated. A detailed study on the heterogeneous polymerization initiated by triethyl aluminum was carried out. A reaction mechanism is suggested on the basis of chemical analysis of the polymer.     

Soluble bimetallic μ-oxoalkoxides. IX. ε-caprolactone and β-propiolactone block copolymerization

The fast and living ring-opening polymerization of lactones by bimetallic μ-oxoalkoxides in homogeneous organic phase has led to successful block copolymerization. The catalyst is coordinatively associated in organic media; however, interaction with lactones can induce, following their nature, different rearrangements of the catalytic aggregates, depending on the nature of these lactones. Consequently, ε-caprolactone and β-propiolactone block copolymers are quantitatively obtained only in the presence of a completely dissociated catalyst.     

Reaktionen mit γ-Chloracetessigesterderivaten

Reactions with derivatives of γ-chloroacetoacetic acid Ethyl γ-chloroacetoacetate reacts with ammonia to give ethyl β-amino-γ-chloro-crotonate; with aniline, however, β-anilino-crotonic acid γ-lactone is formed. The reaction of ethyl α-cyano-γ-chloro-acetoacetate with arylamines yields 1-aryl-2-amino-3-ethoxycarbonyl-pyrrolin-4-ones.     

Synthese von diastereo- und enantio-selektiv deuterierten β,ε-, β,β-, β,γ- und γ,γ-Carotinen

Synthesis of Diastereo- and Enantioselectively Deuterated β,ε-, β,β-, β,γ- and γ,γ-Carotenes We describe the synthesis of (1′R, 6′S)-[16′, 16′, 16′-²H₃]-β, εcarotene, (1R, 1′R)-[16, 16, 16, 16′, 16′, 16′-²H₆]-β, β-carotene, (1′R, 6′S)-[16′, 16′, 16′-²H₃]-γ, γ-carotene and (1R, 1′R, 6S, 6′S)-[16, 16, 16, 16′, 16′, 16′-²H₆]-γ, γ-carotene by a multistep degradation of (4R, 5S, 10S)-[18, 18, 18-²H₃]-didehydroabietane to optically active deuterated β-, ε- and γ-C₁₁-endgroups and subsequent building up according to schemes \documentclass{article}\pagestyle{empty}\begin{document}${\rm C}_{11} \to {\rm C}_{14}^{C_{\mathop {26}\limits_ \to }} \to {\rm C}_{40} $\end{document} and C₁₁ → C₁₄; C₁₄+C₁₂+C₁₄→C₄₀. NMR.- and chiroptical data allow the identification of the geminal methyl groups in all these compounds. The optical activity of all-(E)-[²H₆]-β,β-carotene, which is solely due to the isotopically different substituent not directly attached to the chiral centres, is demonstrated by a significant CD.-effect at low temperature. Therefore, if an enzymatic cyclization of [17, 17, 17, 17′, 17′, 17′-²H₆]lycopine can be achieved, the steric course of the cyclization step would be derivable from NMR.- and CD.-spectra with very small samples of the isolated cyclic carotenes. A general scheme for the possible course of the cyclization steps is presented.     

Stoffwechselprodukte von Mikroorganismen 74. Mitteilung [1]. Synthese des Ferrichroms. 1. Teil: (S)-α-Amino-δ-nitr-ovaleriansäure (δ-Nitro-L-norvalin)

(S)-α-Amino-δ-nitropentanoic acid (δ-nitro-L -norvaline), an intermediate of the total synthesis of ferrichrome, was synthesized starting from diethyl oxalate and γ-butyrolactone.     

16α,17α‐Epoxy‐20‐oxopregn‐5‐en‐3β‐yl acetate

The title compound, C₂₃H₃₂O₄, has a 3β configuration, with the epoxy O atom at 16α,17α. Rings A and C have slightly distorted chair conformations. Because of the presence of the C5=C6 double bond, ring B assumes an 8β,9α‐half‐chair conformation slightly distorted towards an 8β‐sofa. Ring D has a conformation close to a 14α‐envelope. The acetoxy and acetyl substituents are twisted with respect to the average molecular plane of the steroid. The conformation of the mol­ecule is compared with that given by a quantum chemistry calculation using the RHF–AM1 (RHF = Roothaan Hartree–Fock) Hamiltonian model. Cohesion of the crystal can be attributed to van der Waals interactions and weak intermolecular C—H?O interactions, which link the mol­ecules head‐to‐tail along [101].     

On the mechanism of isomerization reactions in the esters of some simple α,β-unsaturated carboxylic acids

It is shown from a detailed examination of first field free region metastable peak shapes that the molecular ion of the methyl ester of acrylic acid rearranges into 2- and 3-butenoic acid ions prior to metastable fragmentations involving the losses of H₂O, CH₃˙ and CO. The key intermediate ion in this ester-acid isomerization is shown to be the enol form of ionized γ-butyrolactone. The C-5 homologues methylmethacrylate and ethylacrylate display a similar mechanism for H₂O loss, but the loss of CH₃˙ shows additional mechanistic complexities. It was shown from the metastable peak shapes of ¹³C and deuterium labelled compounds that the larger part of the methyl loss does not occur from acid type ions, but directly from methyl substituted enol ions of γ-butyrolactone. The mechanistic proposals also account for the presence of a pronounced loss of CH₃˙ from the isomeric ester methylcrotonate and the absence of H₂O loss in both methylcrotonate and the methyl ester of 3-butenoic acid.     

Selective synthesis of structurally isomeric poly-β-ester and poly-δ-ester from β-(2-acetoxy-ethyl)-β-propiolactone with Al and Zn catalysts

It was found that structurally isomeric polymers were formed by the ring-opening polymerization of β-(2-acetoxy ethyl)-β-propiolactone with (EtAlO)_n and Et(ZnO)₂ZnEt catalysts; that is, the Al catalyst catalyzed normal polymerization which led to poly-β-ester and the Zn catalyst formed isomerized poly-β-ester as the main product. The polymer structure was determined by nuclear magnetic resonance (NMR), T₁-value, thermal decomposition product, and (T_g). The NMR studies for the monomer–catalyst systems indicated that the Al catalyst interacted predominately with the lactone group, whereas the Zn catalyst interacted with the side-chain ester group. These site-selective interactions could be related to the difference in the stereoregulation by the two catalysts during the poly(β-ester)-forming polymerization process.