The Preparation of β-Cycloalkyl-L-Aspartate and γ-Cycloalkyl-L-Glutamate by Enzymatic Hydrolyses

The simple method to prepare the β-cycloalkyl aspartate and γ-cycloalkyl glutamate by enzymatic reactions has been developed. Compared with conventional chemical methods, the enzymatic method is more facile.     

Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source

A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX₃ (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition.     

A Mild Isomerization Reaction for β,γ‐Unsaturated Ketone to α,β‐Unsaturated Ketone

A series of β,γ‐unsaturated ketones were isomerized to their corresponding α,β‐unsaturated ketones by the introduction of DABCO in iPrOH at room temperature. The endo‐cyclic double bond (β,γ‐position) on ketone was rearranged to exo‐cyclic double bond (α,β‐position) under the reaction conditions.     

α‐ and β‐Relaxations in neat and antiplasticized polybutadiene

Dielectric spectroscopy was carried out to measure the α‐relaxation (local segmental motion) and the higher frequency, secondary relaxation (β‐mode) in 1,4‐polybutadiene, both neat and containing a nonpolar diluent, mineral oil. The α‐relaxation shifted to lower frequencies (antiplasticization) in the presence of the diluent, suggesting the glass temperature of the latter is higher than the T_g of the polymer (i.e., >187K). The T_g of neat mineral oil cannot be determined directly, due to crystallization. While the diluent increased the magnitude of the α‐relaxation times, it had no effect on the β‐relaxation. Moreover, neither the shape of the α‐relaxation function nor its temperature dependence was influenced by the diluent. From this we conclude that the main effect of the mineral oil was to increase the local friction, without changing the degree of intermolecular cooperativity of the molecular motions. We also find that near the glass temperature, there is rough agreement between the time scale of the secondary relaxation process and the value of a noncooperative relaxation time estimated from theory. This approximate correspondence between the two relaxation times also holds for 1,2 polybutadiene. However, the β‐process cannot be identified with the noncooperative α‐relaxation, and the relationship between them is not quantitative. © 2000 John Wiley & Sons, Inc.* J Polym Sci B: Polym Phys 38: 1841–1847, 2000     

Photoinduced transformation of α,β-epoxyketones to β-hydroxyketones by Hantzsch 1,4-dihydropyridine

Irradiation (λ >300 nm) of Hantzsch 1,4-dihydropyridine with aromatic α,β-epoxyketones in acetonitrile selectively breaks the Cα---O bond of the epoxides giving the corresponding β-hydroxyketones in excellent yields.     

Synthesis of new optically active α,α′,β‐trisubstituted‐β‐lactones as monomers for stereoregular biopolyesters

Various optically active (4R)‐alkyloxycarbonyl‐3,3‐dialkyl‐2‐oxetanones as monomers were synthesized from L‐(S)‐malic acid in six steps to prepare a new family of stereopolyesters for biomedical applications. The synthesis began with an esterification followed of a dialkylation in the aim to introduce hydrophobic groups as methyl or reactive group as allyl. Then, a saponification has permitted to obtain the corresponding diacids that reacted with appropriate alcohols to furnish different monoesters. The last and most important step was activation of hydroxyl group of monoesters with the asymmetric carbon configuration inversion according to the Mitsunobu reaction. Thus, this reaction has provided lactones from monoesters with 100% enantiomeric excess which was confirmed by ¹H NMR and by the synthesis of corresponding isotactic and semicrystalline homopolyesters. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2586–2597     

TBAF‐Mediated Dimerization Reaction of β,γ‐Unsaturated Arylketones

A simple and high‐yield method for the synthesis of several 1,5‐diaryl‐1,5‐dicarbonyl compounds has been established starting from TBAF‐mediated isomerization and dimerization reaction of β,γ‐unsaturated arylketones (allyl arylketones) with mono‐, di‐, and tri‐methoxy groups, which is derived from allylation of commercially available different benzaldehydes and followed by oxidation of the resulting secondary alcohols.     

Studies on the Mass Spectra of N‐Aryl α,β‐Unsaturated γ‐Lactams

The mass spectra of a series of N‐aryl α,β‐unsaturated γ‐lactams were studied. Besides the molecular ion, the three characteristic fragments such as [M⁺‐29], [M⁺‐55], and [M⁺‐82] were commonly found in a series of N‐Aryl α,β‐unsaturated γ‐lactams in EI/MS. Further more the mechanism for the interpretation of these fragments is also de scribed.     

Heat-resistant resins obtained from polymer precursors bearing β,β′-dicyanovinyl terminal groups

Certain polymer precursors of the general formula: where A is an aromatic structure bearing ester, amide, azomethine, or imide linkages were synthesized. Particularly, 4-hydroxybenzaldehyde was condensed with malonitrile to afford 4-hydroxy-β,β′-dicyanostyrene which reacted with a half molar amount of terephthaloyl dichloride in the presence of an acid acceptor. In addition, 3-nitrobenzaldehyde was condensed with malonitrile to yield 3-nitro-β,β′-dicyanostyrene that was catalytically hydrogenated to the corresponding amine. The latter reacted with a half molar amount of terephthaloyl dichloride, terephthaldehyde, pyromellitic dianhydride, or benzophenone tetracarboxylic dianhydride. The polymer precursors were characterized by elemental analyses as well as IR and ¹H-NMR spectroscopy. Their curing behavior was investigated by DTA. Crosslinked polymers were obtained by curing the monomers at 300°C for 24 h. They were stable up to 407–437°C in N₂ and afforded an anaerobic char yield of 65–50% at 800°C. The thermal stability of resins was correlated with their chemical structures. © 1993 John Wiley & Sons, Inc.     

Synthesis of α,β-unsaturated ketone from α-iodo ketone using photoirradiation

Irradiation of α-iodo ketone in hexane under a nitrogen atmosphere with a high-pressure mercury lamp (λ>300nm) at room temperature afforded the corresponding α,β-unsaturated ketones in good yield. This reaction affords a new, clean and convenient synthetic method for the α,β-unsaturated ketone.     

Fluorinated β-Sultones

Fluorinated (β)-sultones are formed on addition of sulfur trioxide to fluorinated olefins. Tetrafluoroethanesultone has been studied particularly thoroughly. The title compounds are characterized by the ease with which they undergo ring cleavage to give, e.g., derivatives of α-sulfo carboxylic acids, of sulfonic acids, of carboxylic acids, and of sulfuric acid. Fluorinated compounds of this type containing an α-hydrogen atom are especially valuable in preparative work.     

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.     

Synthesis of Phenanthrene Derivatives through the Reaction of an α,α‐Dicyanoolefin with α,β‐Unsaturated Carbonyl Compounds

Phenanthrene derivatives were prepared by reacting an α,α‐dicyanoolefin with different α,β‐unsaturated carbonyl compounds resulting from Wittig reaction of ninhydrin and phosphanylidene or condensation of barbituric acid and an aldehyde. The easy procedure, mild and metal‐catalyst free, reaction conditions, good yields, and no need for chromatographic purifications are important features of this protocol. The structures of the product of type 3 and 5 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS). A plausible mechanism for this type of reaction is proposed (Scheme 1).     

Photolysis of α,β‐Epoxyketones: A Green Synthesis of β‐Hydroxyenones through Tandem H‐Abstraction,Ring Cleavage and Isomerisation

The photochemical behavior of various substituted epoxycarbonyl compounds consisting of more than one possible photo‐labile site (i.e. δ‐hydrogen, β‐hydrogen and epoxide ring) has been investigated. These compounds on photo‐irradiation produced the β‐hydroxyenones in an eco‐friendly green approach. Mechanistically, these photo‐transformations have been envisaged to occur via an intramolecular β‐hydrogen abstraction by the carbonyl group of benzoyl moiety to generate the 1,3‐biradical followed by epoxide ring opening that isomerizes into the photoproducts. The photolysis of the probed epoxy ketones didn’t furnish any photoproduct through δ‐hydrogen abstraction, whatsoever. This exclusive preference for β‐H abstraction over δ‐H abstraction by carbonyl group has been vindicated by the MM2 energy mini‐ mized program for the investigated photochemical substrates. The structures of these photoproducts were established from the analysis of their spectral parameters (IR, ¹H/¹³C NMR and Mass) and single crystal X‐ray crystallography data.     

Synthesis of novel α,α′,β-trisubstituted β-lactones

A concise and efficient synthesis of α,α′,β-trisubstituted β-lactones is presented. These novel lactones are easily obtained in five steps and will be dedicated to anionic ring opening polymerization.     

NH2SO3H–SiO2 as a new water‐compatible,recyclable heterogeneous catalyst for the synthesis of novel (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction

NH₂SO₃H–SiO₂/water as a novel catalytic system was used for the synthesis of (α,β‐unsaturated) β‐amino ketones via aza‐Michael reaction at reflux conditions. The methodology was of general applicability and the catalyst exhibited activity up to five cycles. The catalyst was characterized for the first time using FT‐IR, X‐ray diffraction and scanning electron microscopic–energy dispersion analytical X‐ray. The stability of the catalyst was evaluated by differential scanning calorimetry and TGA/differential thermal analysis. High efficiency of the catalyst along with its recycling ability and the rather low loading demonstrated in reactions are the merits of the presented protocol. Copyright © 2013 John Wiley & Sons, Ltd.