Tandem retro-aldol/Wittig/Michael and related cascade processes

A number of novel tandem sequences initiated by a retro-aldol process are described along with preliminary scope and limitation studies. These include (i) retro-aldol/Wittig trapping/intramolecular Michael addition, (ii) retro-aldol/aza-Wittig/intramolecular imine addition, (iii) retro-aldol/Henry/intramolecular Michael addition and (iv) retro-aldol/Knoevenagel/intramolecular Michael addition sequences. A range of novel functionalised cyclopentanes, and related systems, are described which should prove to be useful synthetic building blocks.     

Enantio- and diastereoselective Michael reaction of 1,3-dicarbonyl compounds to nitroolefins catalyzed by a bifunctional thiourea

We synthesized a new class of bifunctional catalysts bearing a thiourea moiety and an amino group on a chiral scaffold. Among them, thiourea 1e bearing 3,5-bis(trifluoromethyl)benzene and dimethylamino groups was revealed to be highly efficient for the asymmetric Michael reaction of 1,3-dicarbonyl compounds to nitroolefins. Furthermore, we have developed a new synthetic route for (R)-(-)-baclofen and a chiral quaternary carbon center with high enantioselectivity by Michael reaction. In these reactions, we assumed that a thiourea moiety and an amino group of the catalyst activates a nitroolefin and a 1,3-dicarbonyl compound, respectively, to afford the Michael adduct with high enantio- and diastereoselectivity.     

Aluminium–SALEN complex: a new catalyst for the enantioselective Michael reaction

A new heterobimetallic complex prepared from a chiral SALEN ligand and Red-Al® was found to catalyse the Michael reaction between various dialkyl malonates and cycloalkenones to give products in high yields with e.e.s of up to 58%.     

Iodine-catalyzed Michael addition of mercaptans to α,β-unsaturated ketones under solvent-free conditions

A simple and efficient method for the Michael reaction between various mercaptans and α,β-unsaturated ketones using a catalytic amount of iodine (5 mol %) to generate the 1,4-adduct has been reported. The significant features of the iodine catalyzed Michael addition are (a) operational simplicity, (b) inexpensive reagents, (c) high yields of products, (d) the use of relatively low or nontoxic reagents and (e) solvent-free conditions.     

Synthesis of the Stereoisomers of the Sex Pheromones of the Southern Corn Rootworm

ＩｎｔｒｏｄｕｃｔｉｏｎＣｈｉｒａｌｉｔｙｄｕｅｔｏｍｅｔｈｙｌｂｒａｎｃｈｉｎｇｉｓａｂｕｎｄａｎｔａｍｏｎｇｓｅｖｅｒａｌｎａｔｕｒａｌｌｙｏｃｃｕｒｉｎｇｓｅｃｏｎｄａｒｙｍｅｔａｂｏｌｉｔｅｓ.Ｔｈｉｓｓｔｒｕｃｔｕｒａｌｆｅａｔｕｒｅｉｓｐａｒｔｉｃｕｌａｒｌｙｐｒｅｄｏｍｉｎａｎｔａｍｏｎｇｉｎｓｅｃｔｐｈｅｒｏｍｏｎｅｓ[1] ,ｍａｎｙｏｆｗｈｉｃｈａｒｅｏｆｅｃｏｎｏｍｉｃｓｉｇｎｉｆｉｃａｎｃｅ .Ａｓａｃｏｎｓｅｑｕｅｎｃｅ ,ａｃｏｎｓｉｄｅｒａｂｌｅｅｆｆｏｒｔｈａｓｂｅｅｎｍａ…     

Peptide-phospholipid cross-linking reactions: Identification of leucine enkephalin-alka(e)nal-glycerophosphatidylcholine adducts by tandem mass spectrometry

The covalent interactions between peptides and lipid oxidation products, with formation of Schiff and Michael adducts, are known to occur during free radical oxidative damage. In this study, leucine-enkephalin-glycerophosphatidylcholine alka(e)nal adducts were analyzed by electrospray tandem mass spectrometry (MS/MS). Upon collision-induced dissociation of the Leucine enkephalin-2-(9-oxo-nonanoyl)-1-palmitoyl-3-glycerophosphatidylcholine, an alkanal Schiff adduct observed at m/z 1187.7, the main product ions were attributed to the phosphocholine polar head and loss of the peptide. Also, product ions resulting from characteristic losses of phosphatidylcholines and cleavages of the peptide chain (mainly b-type) were observed. Additional product ions formed by combined peptide and phosphatidylcholine fragmentations were identified. The fragmentation pattern of the leucine enkephalin-alkanal Schiff adduct and the leucine enkephalin-alkenal phosphatidylcholine Schiff and Michael adducts were similar, although the loss of the peptide for the Michael adduct should occur through a distinct mechanism. These fragmentation pathways differ greatly from those described for peptide-lipid Schiff and Michael adducts, in which only peptide chain cleavages are reported, probably due to charge retention in the glycerophosphatidylcholine polar head in peptide-glycerophosphatidylcholine adducts.     

Signal amplification by conjugate addition for differential sensing with synthetic pores

The Michael addition of hydrazide signal amplifiers to short-lived orthoquinone analytes is introduced as a new method to contribute toward the discrimination of polyphenols (e.g. epigallocatechin gallate, resveratrol) with synthetic pores.     

Condensation of cinnamonitriles with arylacetonitriles

The Michael addition of arylacetonitriles to Michael acceptors such as α,β-unsaturated nitriles occurred with a stoichiometric amount of sodium ethoxide to give only the 1,4-addition product in pure diastereomeric form. The structures of the reaction products were established by infrared, H-1 and C-13 nuclear magnetic resonance spectroscopy as well as by elemental analysis. The diastereomeric purity was determined by chromatographic and NMR measurements using achiral lanthanide shift reagents techniques. The observed resonances did not show any resolution of the diastereomeric proton signals. The stereochemistry and absolute configuration of the condensation product were established from X-ray crystallography.     

Cyclization reactions of 1-[3'-hydroxy-2'-(hydroxymethyl)prop-1'-enyl]pyrimidine nucleobases: intramolecular Michael additions to the C(5)=C(6) bonds and intramolecular dehydrations

The tendency of a series of acyclic nucleoside analogues 1a-f to undergo intramolecular cyclization reactions was investigated. All compounds, when treated with NaOD, were in equilibrium with the bicyclic compounds 2a-f, arising from Michael addition of a hydroxy group to the C(5)=C(6) bonds. Derivatives of 2,4-pyrimidinediones (1a,b) had the highest tendency to undergo intramolecular Michael addition when treated with triethylamine, whereas the cyclization of 4-amino-2-pyridones (1c-f) proceeded best with acid. The exocyclic double bond of was essential for the cyclization to occur. Commonly used N-protecting groups as the benzoyl- and the dibutylaminomethylene group enhanced cyclization. Under acidic anhydrous conditions 1b and 1e cyclized to the 2,4'-anhydro compounds 1b and 1e.     

Enantioselective solution- and solid-phase synthesis of glutamic acid derivatives via Michael addition reactions

The enantioselective conjugate addition of Schiff base ester derivatives to Michael acceptors either in solution (56–89% e.e.) or on solid-phase (34–82% e.e.) gave optically active unnatural α-amino acid derivatives. The reaction was conducted in the presence of chiral, non-racemic quaternary salts derived from the cinchona alkaloids using neutral, non-ionic phosphazene bases.     

The effects of primary amine catalyzed thio-acrylate Michael reaction on the kinetics, mechanical and physical properties of thio-acrylate networks

Thio-acrylate networks were prepared using two methods. The first method involved the in-situ photopolymerization of a multifunctional thiol mixed with a multifunctional acrylate in the presence of a photoinitiator (photo-cure only), while the second method utilized an extremely efficient thio-acrylate Michael reaction followed by the photopolymerization of unreacted acrylate functional groups (amine catalysis/photo-cure). The thio-acrylate Michael reaction was catalyzed by a primary amine that promoted a rapid 1-to-1 Michael addition reaction of thiol to acrylate. Kinetic analysis via real-time infrared (RTIR) spectroscopy verified the 1-to-1 addition, the rates of the thio-acrylate Michael reaction and the total incorporation of the thiol into the networks at various concentrations when the amine catalyst was used. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) data show very narrow glass transition temperatures for the networks prepared when the amine catalysis/photo-cure sequence was used. The two step sequential process can be used to target network films that can be tailored to have high energy damping properties at a given temperature, e.g., room temperature. Finally, in all cases, whether the photo-cure only or the amine catalysis/photo-cure process was used, the glass transition temperature increased with the initial acrylate feed concentration.     

Michael addition of N-isobutylidene-t-butylamine to dimethyl methoxymethylenemalonate and a new synthesis of some fused pyrazole derivatives from the adduct

N-Isobutylidenemethylamine reacted with dimethyl methoxymethylenemalonate to afford the N-alkylation product 3a exclusively. Exchanging the N-substituent of the Schiff's base from methyl to t-butyl altered the course of the reaction, allowing Michael addition to take place predominantly. The Michael adduct 4c on reaction with hydrazinoalkanols 6a,b, 6c,d and 6e gave tetrahydropyrazolo[5,1-b]oxazoles 9a,b , tetrahydro-pyrazolo[5,1-b][1,3]oxazines 9c,d and hexahydropyrazolo[5,1-b][1,3]oxazepine 9e , respectively.     

Asymmetric michael additions of ester enolates to enantiomerically pure vinylic sulfoxides: Synthesis of 3-substituted glutarate esters in high enantiomeric purity

Various ester enolate ions add as Michael donors to enantiomerically pure Michael acceptor cycloalkenone sulfoxides 1a and 1b and unsaturated lactone sulfoxides 3a and 3b. The level of asymmetric induction in some cases is extraordinarily high (95% e.e. of final 1,5-dicarbonyl products). Adduct ester lactones 5 and 6 can be converted easily into some synthetically versatile, trifunctional, 3-substituted glutarate esters of high enantiomeric purity. An efficient route to enantiomerically pure pentenolide sulfoxide (S)-(+)-3b is presented.     

Towards the development of synthetic routes using theoretical calculations: an application of in silico screening to 2,6-dimethylchroman-4-one

This study describes an attempt to develop a synthetic route using theoretical calculations, i.e., in silico synthesis route development. The KOSP program created four potential synthetic routes for generating 2,6-dimethylchroman-4-one. In silico screening of these four synthetic routes was then performed. In silico screening involves theoretical analysis of synthetic routes prior to actual experimental work. A synthetic route using the Mitsunobu reaction had already been reported by Hoddgets et al. Theoretical investigations were also conducted on two S(N)Ar reactions as well as a Michael reaction before they were examined experimentally. In silico screening using DFT calculations indicated that only the Michael reaction was likely to produce the target. Experimental work confirmed that the target was obtained in a yield of 76.4% using the Michael reaction. The other two routes, except for the Mitsunobu reaction, failed to generate the target. Our results demonstrate that theoretical calculations can be used to narrow down the number of experiments that need to be conducted when developing novel synthetic routes.     

迈克尔反应受体分子化学生物学研究

迈克尔受体是烯键或炔键与吸电子基团共轭相连形成的官能团,含有这样官能团的化学小分子能与亲核试剂发生迈克尔加成反应,因此称为迈克尔反应受体分子。迈克尔反应受体分子是一类重要的生理活性分子,它们直接或间接参与许多生命过程,同时也是细胞中许多信号转导途径的调节者,在化学生物学研究中起着重要的作用。本文对迈克尔反应受体分子化学生物学研究进展进行了综述。     

Michael reactions carried out using a bench-top flow system

The Michael reaction between methyl 1-oxoindan-2-carboxylate and methyl vinyl ketone was achieved successfully by pumping solutions of the reactants in toluene through a fluid bed of Amberlyst A21 at 50 degrees C. The use of a fluid bed reactor is attractive as it allows gel-type beads, i.e. the type of bead used in most studies of polymer-supported (PS) organic reactions, to be used satisfactorily in a flow system. When polymer-supported cinchonidine was used in place of Amberlyst A21, the Michael product was obtained in high yield with an enantiomeric excess (ee) of 51%. This % ee is comparable to that achieved when the reaction was catalysed by cinchonidine itself.     

3-疏基香豆素及其衍生物的研究

研究了3-疏基香豆素(8)、3,3'-二硫代双香豆素的合成及8与一系列Michael受体的反应.按受体结构不同,除都能发生分子间的加成反应外,有些还可进一步发生第二次分子内的加成反应,关环后得到一系列四氢噻吩并[2,3-C][1]苯并吡喃-4(H)-酮的衍生物.对这些化合物的立体化学及结构进行了鉴定.8分别和烯丙基溴、肉桂基溴缩合,前者在N,N-二甲苯胺内发生正常的Claisen重排,得到1,2-二氢-2-甲基噻吩并[2,3-C][1]苯并吡喃-4-(H)-酮及1,2,3,5-四氢硫代吡喃并[2,3-C][1]苯并吡喃-5-酮,但后者的反应产物是3-(ρ-N,N-二甲氨基)苄硫基香豆素.     

The unprecedented reaction of dimethylsulfonium methylide with Michael acceptors: synthesis of 1-substituted vinyl silanes and styrenes

Rather than the usual cyclopropanation, conditions for an unprecedented elimination reaction from the adduct of dimethylsulfonium methylide and various Michael acceptors have been established leading to functionalized 1-substituted alkenes. In silyl substituted substrates (2a and 2h), where a facile Peterson-type olefination is possible from the adduct; elimination took place instead to give functionalized 1-substituted vinyl silanes. Aryl substituted Michael acceptors (2b-e, 2g and 2i-k) also underwent a similar kind of olefination to give 1-substituted styrene derivatives with moderate yields along with a side product, which arose by nucleophilic demethylation from the adduct of dimethylsulfonium methylide and arylidene malonates. Hammett studies revealed that selectivity for olefination vs. demethylation increases as the aryl substituent becomes more electron deficient. Alkylidene malonates (2f and 2l) with a beta-alkyl substituent did not favour the olefination process. Sequential addition of Michael acceptors and alkyl halides to a mixture of dimethylsulfonium methylide and sodium dimsylate provided olefination followed by alkylation on the active methine group. A mechanistic pathway has been formulated from the studies of a few sulfonium methylides.     

含硫碳负离子的反应及其应用的研究: III, 合成戊烯二酸酯类的新方法

本文研究了在碳酸钙或碳酸钾存在下, 由Michael加成物与四氯化碳或甲苯一起加热, 以92-94%的产率得到戊烯二酸酯, 而Michael加成物与碳酸钾在上述溶剂中一起加热得70-100℃范围内, 可得到异构化的消除产物, 产率83-93%。     

Sodium tetramethoxyborate: an efficient catalyst for Michael additions of stabilized carbon nucleophiles

Sodium tetramethoxyborate, easily prepared by reaction of inexpensive sodium borohydride with methanol, possesses a suitable combination of a Lewis base and a Lewis acid to catalyze Michael reactions at room temperature under practically neutral conditions. This reaction provides good to excellent yields of Michael addition products from a broad scope of Michael donor and Michael acceptor reagents.