A general approach for the synthesis of 5-substituted-4-amino-pyrrolidin-2-ones and 5-substituted-4-amino-3-pyrrolin-2-ones

Short stereoselective syntheses of both 5-substituted-4-amino-pyrrolidin-2-ones and 5-substituted-4-amino-3-pyrrolin-2-ones from natural α-amino acids are described.     

Gas-phase elimination reactions of 4-substituted-2-alkoxythiazoline-5-ones

Gas-phase eliminations of 4-substituted-2-alkoxythiazoline-5-ones have been studied. These compounds eliminate via a six-membered transition state to produce 4-substituted-thiazolidine-2,5-diones. These eliminations are unimolecular first-order reactions. Utilization of this thermolysis reaction in the synthesis of new 4-substituted-thiazolidine-2,5-diones is considered. Additional mechanistic information was obtained by comparing the kinetic data for thermal elimination reactions of these compounds with that of 1-ethoxythiazole. © 1996 John Wiley & Sons, Inc.     

Michael addition-elimination reactions of chiral enolates with ethyl 3-halopropenoates

Key dienoic or dienal substructures of cytotoxic macrolides amphidinolide E and dictyostatin have been prepared via a Michael addition (followed by elimination of X-) of chiral enolates on beta-halo derivatives of ethyl acrylate, with full retention of the initial E or Z configuration. Evans oxazolidin-2-ones and our related thiazolidin-2-ones, as well as a fine-tuning of the reaction conditions, have been essential. Many chiral building blocks are accessible from these adducts.     

Efficient synthesis of 5-substituted-4,5-dihydro-1,2,4-triazin-6-ones and 5-substituted-1,2,4-triazin-6-ones

Treatment of methyl α-(dimethylarninomethyleneamino)carboxylates 1 (from α-amino acids and dimethylformamide dimethylacetal) with hydrazine gives 5-substituted-4,5-dihydro-1,2,4-triazin-6-ones 2 , which are smoothly dehydrogenated to 5-substituted-1,2,4-triazin-6-ones 3 with potassium permanganate in acetone/acetic acid.     

DABCO-catalyzed synthesis of 3-substituted-3-hydroxyindolin-2-ones in aqueous media

An efficient and greener protocol for easy access to 3-susbstituted-3-hydroxy-2-oxindoles by the reaction with various substituted isatins and acetophenones is described. This protocol is widely applicable for a variety of isatins and acetophenones using water as a reaction media and 1,4-diazabicyclo[2.2.2]octane (DABCO) as catalyst with shorter reaction time and good to excellent yield of products.     

Stereocontrolled ring-opening of a hindered sulfamidate with nitrogen-containing aromatic heterocycles: synthesis of chiral quaternary imidazole derivatives

This paper explores the role of a hindered cyclic sulfamidate derived from α-methylisoserine as an electrophile in a nucleophilic displacement reaction with nitrogen-containing aromatic heterocycles. Several imidazoles and pyrazole were tested as nucleophiles in the absence of an additional base to give the corresponding ring-opening compounds. We show that the process takes place by inversion of the configuration of the quaternary electrophilic center, retaining the enantiomeric excess of the starting sulfamidate. This reaction opens the way to obtain important quaternary imidazole derivatives such as an innovative type of bis-amino acid related to histidinoalanine and a novel α,α-disubstituted β-amino acid (β(2,2)-amino acid).     

Convenient synthesis of 1,3-substituted-6-phenylpiperazin-2-ones

The convenient preparation of novel 6-phenylpiperazin-2-ones from simple starting materials via a practical two-step procedure is presented. This methodology involves an initial alkylation of 2-bromoacetophenone with an amino ester followed by a one-pot reductive amination and cyclization step to furnish the desired substituted piperazinones.     

Stereoselective reactions of chiral enolates. Application to the synthesis of (+)-prelog-djerassi lactonic acid.

The application of chiral metal enolates 3 and 4 have been employed in an efficient synthesis of (+)-Prelog-Djerassi lactone (1).     

Isothiazoles IX. Halogenation of 2-substituted-4-isothiazolin-3-ones

Bromination of 4-isothiazolin-3-ones, I, gave the 4-bromo derivatives, III, in good yields, while formation of 4,5-dibromo derivatives, IV, was much more difficult. In contrast, chlorination of I, even under mild conditions, gave primarily 4,5-dichloro derivatives, VI, and lesser amounts of the 4-chloro derivatives, V. Vigorous bromination of the 4-methyl analog of I gave the 5-bromo derivatives, VIII, whereas mild chlorination gave predominantly the 4,5,5-trichloro derivatives, X.     

Reactivity of cyclic sulfamidates towards sulfur-stabilised enolates. Stereocontrolled synthesis of functionalised lactams

A structurally representative series of 1,2- and 1,3-cyclic sulfamidates react with enolates derived from methyl alpha-phenylthioacetate 9b to give 5- and 6-substituted alpha-phenylthio lactams 20-24. These products provide, via the corresponding sulfoxides, an entry to alpha,beta-unsaturated lactams e.g. 12, 27, 29 and their alpha-phenylthio analogues e.g. 26 and 30. With the enantiomerically pure 1,2-cyclic sulfamidates 10, 15 and 17, these reactions all proceed with no detectable loss of stereochemical integrity.     

Development of catalytic asymmetric reactions via chiral palladium enolates

This article describes the generation of chiral palladium enolates and their application to several kinds of catalytic asymmetric reactions. Two methods to generate chiral enolates were developed using novel cationic palladium complexes 1 and 2 . In these processes, water or a hydroxo ligand on palladium metal plays an important role as a nucleophile to promote the transmetallation or as a Brønsted base to abstract an acidic α‐proton of the carbonyl group. These enolates showed sufficient reactivity with various electrophiles. Using a chiral Pd enolate as a key intermediate, highly enantioselective reactions such as catalytic aldol reactions, Mannich‐type reactions, Michael reactions, and fluorination reactions were developed. The unique structures of the palladium enolate complexes were elucidated and reaction mechanisms are proposed. © 2004 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 4: 231–242; 2004: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20017     

Diversity-oriented synthesis of amino acids using chiral enolates

We report a facile diversity oriented synthesis of α- and β-amino acids, by utilizing the pluripotent α-methylene group in a chiral bicyclic lactam as our key point of transformation.     

Phase-transfer catalysis in reactions of 5-alkyl-3H-furan-2-ones with dichlorocarbene

Treatment of 5-alkyl-3H-furan-2-ones and 5-alkyl-3H-thiophen-2-ones with dichlorocarbene under conditions of phase-transfer catalysis at 20–90 °C results in insertion of the carbene at the C=C bond followed by skeletal rearrangement.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1995–1997, October, 1995.     

Effective synthesis of 5-aryl-3-ethylidene-3H-pyrrol-2-ones

Substituted 5-aryl-3-ethylidene-3H-pyrrol-2-ones were synthesized by the reaction of the corresponding 4-aryl-4-oxobutanoic acids with ketones in the presence of aminating agents. The conditions of this reaction were developed with the use of both the conventional condensation technique and microwave activation. The structures of the reaction products were con-firmed by elemental analysis, IR spectroscopy, and ¹H NMR spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 693–696, April, 2006.     

Reaction of ethyl γ-bromo-β-methoxycrotonate with carbonyl compounds. Synthesis of 4-methoxy-6-substituted-5,6-dihydro-2H-pyran-2-ones and 3-substituted 3-pyrazolin-5-ones

Ethyl β-methoxycrotonate I reacts with substituted carbonyl compounds II in benzene to give 4-methoxy-6-substituted-5,6-dihydro-2H-pyran-2-ones III. The reaction of IIIa and j with hydrazine hydrate in ethanol leads to 3-[(1′-thienyl-1-hydroxy)methyl]-5-hydroxy-1H-pyrazole (IVa) and 3-[1′-styryl-1′-hydroxy)methyl]-5-hydroxy-1H-pyrazole (IVj) in good yields. The structure of the products were assigned and confirmed on the basis of their elemental analysis and the electronic absorption, infrared and nmr spectra.     

The synthesis and reactions of certain 3-substituted-2,1-benzisothiazoles

A new and general synthesis of 2,l-benzisothiazolin-3-ones ( 2 ) is described from the corresponding isatoic anhydride ( 3 ) and potassium hydrogen sulfide which gives the thioanthranilic acid ( 4 ) which is readily oxadized and ring closed to 2 with hydrogen peroxide. Phosphorus oxy-chloride converted 3-hydroxy-2,1-benzisothiazole to 3-chloro-2,1-benzisothiazole which gave a number of different 3-substiluted 2,1-benzisothiazolesby nucleophilic substitution of the 3-chloro group. Rleetrophilie substitution of 1-methyl-2,1 -benzisothiazoIin-3-one ( 2i ) proceeded readily to give the corresponding 5-bromo-, 5-nitro-, and 5-chlorosulfonyl-1-methyl-2,1-benzisothiazolin-3-one. This appears to be a good synthetic route to such 2,1-benzisothiazole derivatives.     

Stereocontrolled synthesis of 3-amino-2-hydroxyalkyl diphenylphosphine oxides mediated by chiral azetidinium salts and epoxyamines

The stereocontrolled synthesis of amino hydroxyalkyl diphenylphosphine oxides has been achieved starting from (2S,3S)-N,N-dibenzyl-3-hydroxy-2-methylazetidinium bromide or (1R),[1′(S)-(dibenzylamino)ethyl]oxirane. The regioselective ring opening of both heterocyclic systems at the less substituted carbon atom with phosphorus nucleophiles proceeded with full stereochemical integrity.     

Synthesis of 5-alkyl-3H-thiolen-2-ones and 5-alkyl-3H-furan-2-ones and condensation reactions at the heterocyclic methylene group

The intramolecular cyclization of -ketocarboxylic acids and their esters gives 5-alkylsubstituted 3H-thiolen-2-ones and 3H-furan-2-ones. It was shown that reaction occurred at the heterocyclic methylene group and that the conditions under which the reaction took place depended on the nature of the heterocyclic atom.Translated from Khimiya Geterotsiklicheskikh Soedinnenii, No. 4, pp. 451–454, April, 1987.     

室温下三光气作环合剂合成5-取代-1,3,4-噁二唑-2-酮类化合物

1,3,4-噁二唑具有抗菌,抗肿瘤,抗惊厥等生物活性~([1-6]),在药物化学方面具有重要的理论意义和实际应用价值.1,3,4-噁二唑类材料具有优良的荧光性和闪烁性和优异的电子传输性能,以及特殊的稳定性和良好的耐热性,被认为是下一代显示器件中载流子输送的首选材料~([7-8]).