Michael addition polymers from 1,4 and 1,3 benzenedimethanol diacetoacetates and tripropylene glycol diacrylate

Summary The Michael reaction was used to synthesize polymers from diacetoacetate esters and the diacrylate of tripropylene glycol. The reaction took place readily, although slowly, at room temperature using 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) as the catalyst. The polymers produced had quite high molecular weights (M_W) in some cases, but the molecular weight distributions were quite broad, particularly in the initial polymer formed. The narrowing of the molecular weight distribution with time can be explained by consideration of the mechanism of the Michael reaction.     

Michael加成反应的研究进展

综述了微波辐射、超声辐射、催化不对称合成以及固相反应等在Michael加成反应中的应用，总结了Michael加成反应的研究进展，并对今后的研究方向提出了建议。     

Exploring the post-polymerization modification of side-chain amino acid containing polymers via Michael addition reactions

An efficacious protocol for the aza-Michael addition of a C-terminus modified phenylalanine side-chain containing polymer (Michael donor) was demonstrated with various Michael acceptors. The aza-Michael addition reactions were carried out at 50 °C in anhydrous methanol, which is a protic solvent, to enhance the advancement of the reactions. ¹H and inverse gated ¹³C NMR spectroscopy were utilized to qualitatively deliver comprehensive data on the reaction progress. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) provided quantitative information about the modification of the polymer. The extent of change in the aza-Michael addition varied with different Michael acceptors and decreased in the order of acrylate > acrylamide > methacrylate. The present study opens up a library of polymers with functional modifications in the side-chain.     

High-molecular weight diepoxide-dicarboxylic acid addition polymers

Summary The addition polymerization of 2,2-bis[4-(2,3-epoxypropoxy)phenyl] propane (DGEBA) and dicarboxylic acid results in high molecular weight addition polymers (M_n 8000–13000). Their molecular weight distribution is rather broad (M_w/M_n=11,6) due to side reactions such as transesterification and formation of ether linkages. Due to the incorporation of the aliphatic dicarboxylic acid moieties in the polymer backbone, the addition polymers show relatively low glass transition temperatures ranging from 26 to 45 °C.     

不对称Michael加成反应的研究进展

综述了近年来催化不对称Michael加成反应的新方法,包括新手性胺催化的不对称加成反应、手性金属配合物催化的反应、手性冠醚催化的反应及其他催化反应.     

Applications of Michael addition chemistry in coatings technology

Since the first filings of patent applications on the use of the Michael addition as crosslinking reaction for coatings around 1984, a lot of research work has been carried out on its application in practical systems. Initial work on the development of coatings for aircraft, car refinishing and timber showed that, especially with urethane acrylate/malonate polyester combinations, the expected high level of durability could be achieved. Further developments in the field of high solids coatings revealed inhibition problems however. They were caused by the interaction of the strong bases, used as the catalysts for the Michael reaction, with acidic ingredients from the substrate and with carbon dioxide from the atmosphere. In principle the problem can be solved by using higher doses of catalyst, but the potlife is too short for general use then. Temporary blocking of the catalysts with an alcohol or with carboxylic acids was investigated as a way to achieve an acceptable potlife. The use of catalysts blocked with carboxylic acids, deblockable with heat or UV light, is a good solution for industrial coatings. Blocking with an alcohol helps to solve the problem of inhibition by carbon dioxide but not the problem of inhibition by the acidic sites in the substrate.     

Michael addition polymerizations of trifunctional amines with diacrylamides

With the aim to get a clear understanding of this category of polymerizations, the Michael addition polymerizations of trifunctional amines, i.e. 4-aminomethyl piperidine (AMPD), N-methyl ethylenediamine (MEDA), and 1-(2-aminoethyl) piperazine (AEPZ), with an equimolar diacrylamide, N,N′-methylene diacrylamide (MDA), were investigated. Similar to the polymerizations of these amines with an equimolar diacrylate, novel linear poly(amido amine)s containing secondary and tertiary amines in the backbones are obtained from these polymerizations as reflected by ¹³C NMR (INVGATE). In situ monitoring the polymerization processes using NMR shows that the reactivity sequence of three types amines in the trifunctional amines is 2° amine (original)>1° amine?2° amine (formed), and the 2° amine (formed) is kept out of the reaction. But these results are different from those reported for the polymerizations of the similar amines with an equimolar divinyl sulfone and some diacrylates. The molecular weights and properties of poly(amindo amine)s obtained were characterized by GPC, DSC and TGA, respectively.     

Preparation of epoxy‐ended hyperbranched polymers with precisely controllable degree of branching by thiol‐ene Michael addition

Epoxy‐ended hyperbranched polymers (EHPs) have a wide range of applications due to their outstanding performances. Because their microstructures are not positively identified, it is very difficult to ascertain the reinforcing and toughening mechanisms of EHPs and their interface interaction with other matrixes. Controllable synthesis of EHPs with precise degree of branching (DB) remains to be a major challenge. Here, a method for preparing novel nitrogen‐phosphor skeleton epoxy‐ended hyperbranched polymers (NPEHP) with controllable DB by a thiol‐ene Michael addition between thiol‐ended hyperbranched polymers (NPHSH) and glycidyl methacrylate have been firstly reported. NPHSH is synthesized by an esterification between hydroxyl‐ended hyperbranched polymers (NPHOH) and 3‐mercaptopropionic acid. NPHOH is prepared by a thiol‐ene Michael addition between methacrylate group of a monomer and thiol group of linear monomer (AB) and/or branched monomer (AB₂). The molar ratio between the AB and AB₂ monomers controls the DB of the products. The ¹H NMR spectra analysis of NPHOH shows that their experimentally determined DBs are very close to their theoretical values, indicating good controllability of their DBs. The narrow molecular weight distributions of NPHOH, NPHSH, and NPEHP suggest high efficiency of the thiol‐ene Michael addition. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44277.     

Polyisobutylene-containing block polymers by sequential monomer addition

Novel poly(acenaphtylene-b-isobutylene-b-acenaphtylene) (PAc-PIB-PAc) triblock copolymers exhibiting thermoplastic elastomer (TPE) properties have been prepared. The synthesis involved the addition of acenaphtylene (Ac) to living polyisobutylene dications (PIB) obtained by living isobutylene (IB) polymerization induced by the dicumyl methyl ether (DiCumOMe)/TiCl₄ initiating system at-80°C. The triblocks contain very short polyacenaphtylene (PAc) blocks (M_n9,000) and consequently yield very soft, low modulus TPEs. Efforts to develop conditions for the living carbocationic polymerization (LCPzn) of Ac have failed.For Part VIII of this subseries see J. P. Kennedy, S. Midha, B. Keszler: Macromolecules (in press)     

Hydroxyapatite: new efficient catalyst for the Michael addition

The synthetic hydroxyapatite is a new basic catalyst for Michael addition of mercaptans to chalcone derivatives with high yields in few minutes and mild reaction conditions. By-products of usual undesirable reactions in Michael addition such as 1.2-addition, bis-addition and polymerisation are not observed. The yields obtained are good to excellent.     

利用Michael加成合成腺嘌呤无环衍生物

以腺嘌呤为起始物,分别和丙烯腈、富马酸二甲酯进行Michael加成反应,得到了两个9-位腺嘌呤衍生物,即6-氨基-9-β-氰乙基嘌呤和2-(9-嘌呤基)富马酸二甲酯,产率分别为97.86%和83.51%.探讨了催化剂种类、溶剂极性和后处理方法等因素对反应的影响,目标产物通过IR、1HNMR进行了结构表征.     

Photopolymerization and initiating mechanism of Michael addition oligomers without photoinitiator

A series of acrylic oligomer which can undergo self-initiation under UV irradiation were synthesized by Michael addition of acetylacetone (acac) with multi-functional acrylates using diazabicycloundecene as catalyst. GC-MS and proton NMR were employed to study the photolysis mechanism of model molecule which was prepared from acac and ethyl acrylate. The β-diketone moiety attached to a fully substituted carbon atom was photoscissile and prone to produce alkyl free radicals by losing acetyl free radical. Polymerization of the acrylated β-diketone-containing oligomers can be thus efficiently triggered regardless of solely irradiated under UV light or blended with pure trimethylolpropane triacrylate. As determined with photo-DSC, the acrylated β-diketone-containing oligomers photopolymerized more slowly than the traditional system of trimethylolpropane triacrylate containing Darocur 1173 at the early stage, but reached a higher final conversion. The rheology measurement showed that the synthesized acrylated β-diketone-containing oligomers exhibited shear thinning property. POLYM. ENG. SCI., 47:1082–1090, 2007. © 2007 Society of Plastics Engineers     

Michael addition of ethyl acrylate and acetone over solid bases

The catalytic behaviour of the superbases Na/NaOH/-Al₂O₃ and Cs_xO/-Al₂O₃ as well as of the basic zeolites Na/NaX and Cs_xO/CsX were investigated in the Michael addition of ethyl acrylate and acetone. The reactions were carried out in the liquid phase at catalyst loadings varying from 0.05 to 0.1 mol ester/g catalyst.     

GPC estimation of molecular mass distribution of addition polymers from bisphenol-a-diglycidyl ether and amines

Thermally polymerized samples of linear addition polymers of bisphenol-A-diglycidyl ether (DGEBA) and the following three different amines (A): benzylamine (BA), p-chloroaniline (PCA), and cyclohexylamine (CHA) were chromatographed by gelpermeation chromatography (GPC) using THF as eluent. The solvation effect of hydroxyl groups by THF has been taken into consideration when calibrating the system and interpreting the chromatograms. The comparison of the chromatograms suggests that the polymer with CHA is cyclized already in the range of small molecular masses (including dimers) and in an early stage of reaction. The comparison of average molecular masses of the samples as measured with independent methods—vapour pressure osmometry (VPO) and GPC—shows that the cyclization of the polymers with BA and PCA takes place to a lower extent, the latter polymer being less capable of cyclization.     

Enhanced fluorescence and thermal sensitivity of polyethylenimine modified by Michael addition

Polyethylenimine (PEI) with enhanced fluorescence and thermal sensitivity was achieved by Michael addition of divinylsulfone (DVS) and N-isopropylacrylamide (NIPAm) respectively. The fluorescence enhancement is quantitatively studied by tailoring the amount of DVS, the medium pH, the substituting acrylates, the substrate polymers with different type amine groups, and the substrate molecular weights. The results suggested that different amine groups affected the performance of fluorescence with quantum yields varied from 0.340 for primary amine (NH₂-) to 0.090 for tertiary amine (N(-C)₃), and further to 0.049 for secondary amine (-NH-). It was also found that the fluorescence enhancement was attributed to the specific molecular structure of DVS-substituted product. The fluorescence moiety is believed to involve a proton-transfer process and have O₂-dependent and pH-sensitive fluorescence properties. From the current study, it can be expected that the accurate prediction of the O₂-dependent fluorescence would be dependent on molecular orbital calculation of the small amine molecules (oxidized with O₂) and their DVS-substituted products.     

KF/Al_2O_3在Michael加成反应中的应用及其机理

综述了KF/Al2O3固体碱催化剂应用于Michael加成反应中,对反应产率和立体构型的影响。论述了该催化剂的表面活性碱位及其在Michael加成反应中的催化机理的研究现状,提出目前普遍认同的几种催化机理,并就此提出自己的观点。     

Synthesis and characterization of hyperbranched poly(ester-amine) by Michael addition polymerization

A series of tertiary amine-based hyperbranched poly(amine-ester)s have been synthesized by Michael addition polymerization of trifunctional monomer, TMEA and difunctional monomer, diacylates in chloroform, and the resultant polymers were subsequently treated with mercaptoethenol or 1-dodecanethiol for improving stability in storage. The caption efficiency of mercaptoethanol is much better than that of 1-dodecanthiol. Kinetic study reveals that the thiol group is consumed faster than the acrylate group when the polymerization with feed molar ratio of diacrylate/TMEA = 2/1 was carried out. At initial polymerization, monomer conversion increases fast, but the molecular weights increase slowly and sharp increase of the molecular weight occurs at the final polymerization. The hyperbranched polymers were well characterized by ¹H NMR spectra and TD-SEC, and DBs of the polymers obtained are between 0.6 and 0.82, as well as the molar ratios of diacrylate/TMEA in the hyperbranched polymers are between 1.60 and 1.82. The fluorescence efficiency and quantum yields of HypET20, HypHT24 and HypDT24 has the following sequence: HypET20 > HypHT24 > HypDT24.     

Promiscuous enzyme‐catalyzed Michael addition: synthesis of warfarin and derivatives

BACKGROUND: Biocatalytic promiscuity has attracted much attention from chemists and biochemists in recent years. Warfarin, one of the most effective anticoagulants, has been introduced for clinical use as a racemate for more than half a century. Although some different chemical strategies towards the synthesis of optically active warfarin have been reported, biocatalytic preparation of warfarin remains unexploited. RESULTS: Lipase from porcine pancreas (PPL) was used as a biocatalyst to catalyze the Michael addition of 4‐hydroxycoumarin to α,β‐unsaturated enones in organic medium in the presence of water to synthesize warfarin and derivatives. The products were obtained in moderate to high yields (up to 95%) with none or low enantioselectivities (up to 28% ee). The influence of reaction conditions including solvents, temperature and molar ratio of substrates was systematically investigated. CONCLUSION: Among the many reported lipase‐catalyzed Michael additions, only a few showed enantioselectivity. Therefore, this Michael addition activity of, for example, PPL is a valuable case of enantioselective lipase catalytic promiscuity. In addition, it was the first time warfarin and derivatives were prepared using a biocatalyst. Copyright © 2012 Society of Chemical Industry     

2-硫代-4-噻唑酮与查尔酮的无溶剂Michael加成反应

以查尔酮和2-硫代-4-噻唑酮为原料,在NaOH存在下无溶剂室温研磨反应,非常方便合成了系列未见文献报道的Michael加成产物.该方法具有反应条件温和、操作简单和产率较高等优点,并通过IR、HNMR、MS和元素分析确证产物的结构.     

In situ formation of biodegradable dextran‐based hydrogel via Michael addition

Vinyl‐sulfone‐functionalized dextran (Dex‐VS) was readily prepared by a single‐batch synthetic procedure at room temperature. The thiol molecule, 1,4‐dithioerythritol (DTE, commercially available) with two terminal thiol groups was used as crosslinking agent. Hydrogels were rapidly prepared in situ by Michael addition under mild physiological conditions. Properties including gelation duration, mechanical modulus, and degradation behavior could be expediently controlled. Moreover, the hydrogels had comparatively low cytotoxicity, and the in vivo tests demonstrated an effective delivery of growth factor. This study might provide a powerful material to be used in tissue regeneration. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013