6051-03-2Relevant academic research and scientific papers
RECYCLABLE POLYMERS BASED ON RING-FUSED GAMMA-BUTYROLACTONES
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Page/Page column 34; 42, (2020/02/23)
The invention discloses a class of new polymers, trans-ring-fused poly(4-hydroxybutyrate)s (RF-P4HB) that exhibit a unique set of properties, including robust thermal stability and mechanical strength, quantitative recyclability to the building block monomers via thermolysis and/or chemical catalysis, and convenient production from the chemical ring-opening polymerization under ambient temperature and pressure. Another unique property is the formation of crystalline stereocomplexed polymers with high melting temperature upon mixing the two enantiomeric RF-P4HB chains via stereocomplexing co-crystallization. This invention also provides the corresponding ring-fused lactone monomer structures that enable the synthesis of the RF-P4HB polymers, through trans-fusing of rings to the parent γ-butyrolactone ring. Furthermore, a polymerization or copolymerization process for the synthesis of RF-P4HB polymers and copolymers is disclosed.
(HMe 2 SiCH 2) 2: A Useful Reagent for B(C 6 F 5) 3 -Catalyzed Reduction-Lactonization of Keto Acids: Concise Syntheses of (-)- cis -Whisky and (-)- cis -Cognac Lactones
Xie, Hengmu,Lu, Ji,Gui, Yingying,Gao, Lu,Song, Zhenlei
supporting information, p. 2453 - 2459 (2017/10/06)
(HMe 2 SiCH 2) 2 has been utilized as a useful reagent for B(C 6 F 5) 3 -catalyzed reduction-lactonization of keto acids to synthesize γ- and δ-lactones. The process led concisely to (-)- cis -whisky and (-)- cis -cognac lactones in respective overall yields of 32% and 36%.
Synthesis of β-Keto Lactone with Basic Skeleton of Przewalskin B
Liu, Jing-Ping,Wang, Li-Qin,Zhao, Yong,Zhao, Yan,He, Ying-Hui,Wang, Zi-Rong,Zhang, Hong-Bin
, p. 1412 - 1415 (2016/09/23)
The synthesis of β-keto lactone was completed using cyclohexanone as starting material. The α,β-unsaturated lactone was obtained through Reformatsky reaction and iodolactonization. The aforementioned lactone was converted into target compound 1 (β-keto lactone) by Nef oxidation and Claisen condensation in six steps with 17.9% overall yield.
Efficient Oxidative Cleavage of Tetrahydrofuran-2-methanols to γ-Lactones by a 2-Iodobenzamide Catalyst in Combination with Oxone
Yakura, Takayuki,Horiuchi, Yuto,Nishimura, Yushi,Yamada, Akihiro,Nambu, Hisanori,Fujiwara, Tomoya
supporting information, p. 869 - 873 (2016/04/05)
An environmentally friendly oxidative cleavage of tetrahydrofuran-2-methanols to the corresponding γ-lactones using a catalytic amount of 2-iodo-N-isopropylbenzamide has been developed. The reaction of various tetrahydrofuran-2-methanols with the catalyst in the presence of Oxone (2 KHSO5·KHSO4·K2SO4) as a co-oxidant in DMF at room temperature successfully affords the corresponding lactones in good to high yields, and recovery of the catalyst is readily accomplished using a reductive work-up. This method is notable because it enables the transformation of tetrahydrofuran-2-methanols to γ-lactones under mild conditions without the use of any toxic heavy metals.
Ruthenium pincer-catalyzed synthesis of substituted γ-butyrolactones using hydrogen autotransfer methodology
Pe?a-López, Miguel,Neumann, Helfried,Beller, Matthias
supporting information, p. 13082 - 13085 (2015/08/18)
The ruthenium pincer-catalyzed synthesis of γ-butyrolactones from 1,2-diols and malonates using borrowing-hydrogen methodology is reported. This regioselective domino-process takes place through catalytic C-C bond formation, followed by intramolecular transesterification. Herein, we show the Ru-MACHO-BH complex as a valuable catalyst in hydrogen autotransfer reactions.
Baeyer-Villiger Oxidation of Cyclobutanones with 10-Methylacridinium as an Efficient Organocatalyst
Xu, Hua-Jian,Zhu, Feng-Fei,Shen, Yong-Ya,Wan, Xin,Feng, Yi-Si
supporting information; experimental part, p. 4145 - 4151 (2012/07/27)
Baeyer-Villiger oxidation of cyclobutanones is achieved in current developed protocol with 10-methylacridinium perchlorate (AcrH +ClO4-) as a novel organocatalyst both with irradiation at room temperature and without irradiation at elevated temperature. Excellent yields of the corresponding lactones are obtained and the possible mechanism has been proposed.
On the stereochemical course of the addition of allylsilanes to aldehydes
Denmark, Scott E.,Weber, Eric J.,Almstead, Neil G.,Wolf, Larry M.
, p. 7701 - 7718 (2012/09/11)
Model compounds 3 and 5 have been studied to determine the orientation of the reacting double bonds in the transition state of the allylmetal-aldehyde addition. These models were designed to remove any intrinsic steric bias for the formation of the bicyclic products that would obfuscate a stereoelectronic contribution to the transition states. Model system 3 revealed a modest preference for the synclinal transition state, albeit in very low yields. Model system 5 underwent selective and largely Lewis acid independent cyclization primarily via a synclinal transition state. The high proximal selectivity observed in these cyclizations likely reflects the selectivity of an unhindered allylmetal-aldehyde addition for the synclinal transition state and results from a stereoelectronic preference, not an intrinsic steric bias, for the synclinal arrangement of double bonds.
Indirect electroreductive cyclization and electrohydrocyclization using catalytic reduced nickel(II) salen
Miranda, James A.,Wade, Carolyn J.,Little, R. Daniel
, p. 8017 - 8026 (2007/10/03)
We describe efforts to achieve the electroreductive cyclization (ERC) and the electrohydrocyclization (EHC) reactions using catalytic nickel(II) salen as a mediator. While nickel(II) salen proved effective, the analogous cobalt complex as well as nickel(II) cyclam were not. The transformations were achieved in yields ranging from 60 to 94% using either a mercury pool or an environmentally preferable reticulated vitreous carbon (RVC) cathode. These examples represent the first instances wherein a nickel salen complex has been used in this manner. Clear differences between the voltammetric behavior of the ERC and EHC substrates were observed. The bisenoate 14, for example, displays a substantially larger catalytic current. When the structurally modified mediator 31 was used, the electron-transfer pathway shuts down. Instead, the reduced form of 31 behaves as an electrogenerated base, leading to the formation of the intramolecular Michael adduct 23. Presumably, the methyl groups of the modified ligand diminish the ability of the reduced form of the complex to serve as a nucleophile but not as a base. Aldehyde 23 was also characterized as a side product of the nickel(II) salen mediated electroreductive cyclization of 11. Given that it is absent from nonmediated processes, its formation is linked to the presence of the mediator. To account for the results, we favor the existence of a mechanistic continuum involving an equilibrium between nickel(II) salen (15) and two reduced forms, one being the metal-centered species 16, the other being a ligand-centered species 17. We postulate that one form may be more prominently involved with the chemistry than another, depending upon the electronic properties/requirements of the substrate, and suggest that the equilibrium will shift to accommodate the need. Thus, for a hard electrophile like an alkyl halide, the properties of 16 ought to dominate, whereas 17 ought to predominate as the reactive species accounting for the chemistry described herein since it properly matches a soft ligand-centered nucleophile with a soft electron deficient alkene.
Rhodium(II)-catalyzed enantioselective intramolecular CH insertion with alkyl diazo(trialkylsilyl) acetates
Mueller, Paul,Lacrampe, Fabienne,Bernardinelli, Gerald
, p. 1503 - 1510 (2007/10/03)
The decomposition of cyclohexyl diazo(triethylsilyl)acetate 2a and the t-butyl derivatives 3a,b with [Rh2{(S)-nttl}4] and similar chiral Rh(II)-catalysts proceeds in toluene at room temperature to produce silylated lactones in up to 90% yield. The reaction is highly stereoselective. Enantioselectivities of up to 79% have been observed.
Nucleophilic Additions to Fused Bicyclic Five-Membered Ring Oxocarbenium Ions: Evidence for Preferential Attack on the Inside Face
Smith, Deborah M.,Tran, Michelle B.,Woerpel
, p. 14149 - 14152 (2007/10/03)
Evidence is provided that nucleophilic attack on five-membered ring oxocarbenium ions occurs from the inside face of the envelope. An eight-five fused-bicyclic system in which two substituents are constrained to pseudoequatorial positions underwent nucleophilic addition with selectivity that was comparable to an unconstrained monocyclic system. On the other hand, a bicyclic six-five analogue underwent reaction with low selectivity. This observation indicates that minimization of eclipsing interactions by attacking inside the envelope is not enough to control selectivity, but that the changes in the overall three-dimensional structure of the ring must be favorable as well. In the bicyclic six-five series, the six-membered ring is accommodated in the cation, but it destabilizes the transition state structure leading to the first-formed product of inside attack.
