Search

An asymmetric synthesis of 2-amino-6,7-dimethoxy-1,2,3,4-tetrahydronaphthalene, which can be converted to the title compound by a literature procedure, is described. The synthesis, starting from 2-...

Two analogs of podophyllotoxin, with the same absolute stereochemistry as the natural product, have been synthesized from the cycloadduct between α-hydroxy-α′-phenyl-o-quinodimefhane and the fumara...

Base-catalyzed hydrolysis of the cycloadduct obtained from the Diels-Alder addition between the α-hydroxy-o-quinodimethane 2 and the spirolactone 3, afforded the new anthracene derivative 6, 1-hydroxy-2-methoxy-4-(3-propanoic acid) anthracene.

A general method for the selective cleavage of tert-butyldimethylsilylethers ortho to a carbonyl group is established by sonication of a 0.1 M solution of the substrate in 1/1 (v/v) CH3OH/CCl4. Other phenolic tert-butyldimethylsilylethers are unaffected. This reaction performed on flavanoids is completed within 3 h and no special workup is required. Other substrates are also investigated and a mechanism is proposed.

The synthesis of 3-amino-6-(hetero)arylpyridazines via palladium catalyzed cross-coupling reactions (Suzuki, Stille) on 3-amino-6-chloropyridazine (1a) and 3-amino-6-iodopyridazine (1b) has been investigated. Comparison of the results shows that there is no need to start from 1b. An improved method for the synthesis of compound 1b from 1a is also described.

The synthesis of 4-aryl-5-methoxy-, 5-aryl-4-methoxy- and 4,5-diaryl-3(2H)-pyridazinones via Suzuki palladium-catalysed cross-coupling reactions with the corresponding chloro-3(2H)-pyridazinones is described.

The synthesis of 3-amino-6-alkoxy- and 3-amino-6-alkylthiopyridazines via nucleophilic aromatic substitution on 3-amino-6-chloropyridazine is described. In contrast to literature reports, no pressure tube is required to perform these reactions.

4,5-Dialkynyl-2-(methyl or phenyl)-3(2H)-pyridazinones (2a–c) were efficiently prepared via Sonogashira cross-coupling reaction on 4,5-dichloro-2-(methyl or phenyl)-3(2H)-pyridazinones (1a,b). Selective Sonogashira reactions were successfully achieved on 4-chloro-2-methyl-5-trifluoromethanesulfonyloxy- (6) and 5-chloro-2-methyl-4-trifluoromethanesulfonyloxy-3(2H)-pyridazinone (11), yielding 5-alkynyl-4-chloro- (7a–c) and 4-alkynyl-5-chloro-2-methyl-3(2H)-pyridazinones (3a,c,e), respectively. Compounds 7a–c and 3a,c,e were subjected to a second Sonogashira reaction giving 4,5-dialkynyl-2-methyl-3(2H)-pyridazinones (8a–c) bearing two different acetylene substituents. Suzuki cross-coupling reaction was also achieved on compounds 7a and 3a producing 4-aryl-5-phenylethynyl- and 5-aryl-4-phenylethynyl-2-methyl-3(2H)-pyridazinones, respectively, in excellent yield.

Suzuki cross-coupling reaction of 2-alkyl(methyl and benzyl)-5-chloro-4-methoxy- and 2-alkyl(methyl and benzyl)-4-chloro-5-methoxypyridazin-3(2H)-ones with 2-formylphenylboronic acid afforded the corresponding biaryl products which were cyclized with ammonia to yield hitherto undescribed pyridazino[4,5-c]isoquinolinones. Removal of the N-benzyl protective group in position 2 yielded the unsubstituted tricyclic pyridazinones.

9/7-α-Carbolines have been prepared via consecutive intermolecular Buchwald-Hartwig reaction and Pd-catalyzed intramolecular direct arylation from commercially available 2,3-dichloropyridines and substituted anilines. The combination of a high reaction temperature (180°C) and the use of DBU were found to be crucial for the intramolecular direct arylation reactions of the 3-chloro-N-phenylpyridin-2-amines as no reaction was observed at 120 °C and 180 °C using different inorganic and other organic bases. On the other hand, nitrogen-methylated pyridine analogues of these substrates {N- [3-chloro-l-methylpyridin-2(1H )-ylidene]anilines} do undergo ring closure at 120°C, with K 3 PO 4 as base, affording the respective 1-methyl-1H-α-carbolines in good yields.

The synthesis of four novel compounds, (i) [(11-{[2-(3-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]amino}-11-oxoundecyl)sulfanyl]acetic acid (4), (ii) N-[5-methyl-2-(3-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]undec-10-enamide (5), (iii) 2-[(11-{[5-methyl-2-(3-nitrophenyl)-4-oxo-1,3-thiazolidin-3-yl]amino}-11-oxoundecyl)sulfanyl]propanoic acid (6) and (iv) 3-[(11-{[2-(3-nitrophenyl)-4-oxo-1,3-thiazinan-3-yl]amino}-11-oxoundecenyl) sulfanyl]propanoic acid (8) from 10-undecenoic acid hydrazide (1) via m-nitrobenzaldehyde-10-undecenohydrazone (2) using mercaptoacetic acid in (i), 2-mercaptopropionic acid in (ii and iii) and 3-mercaptopropionic acid in (iv) is described. The uncyclized products, ({11-[(2E)-2-(3-nitrobenzylidene)hydrazino]-11-oxo-undecyl}sulfanyl)acetic acid (3) and 3-({11-[(2E)-2-(3-nitrobenzylidene)hydrazino]-11-oxoundecyl}sulfanyl)propanoic acid (7) are also obtained in (i) and (iv), respectively. The hydrazones (2), (3) and (7) exist in two conformers as synperiplanar and antiperiplanar. Structural assignment, stereochemistry and biological assays are discussed.

A general synthetic methodology employing heteroaryl-aryl Suzuki coupling is reviewed, by which 15 heteroaromatic ring systems of biological interest have been prepared.

A new synthetic route towards the synthesis of 1,6-dihydro-7H-pyrrolo[2,3-d]pyridazin-7-ones (10a-f) and their regioisomers 1,5-dihydro-4H-pyrrolo[2,3-d]pyridazin-4-ones (9a,b) is described, based on the reaction of 5-alkynyl-4-chloro- (7a,b) and 4-alkynyl-5-chloropyridazinones (8) with different amines (ammonia, methylamine and propylamine) followed by a treatment with a NaOEt solution.

Isocryptolepine (cryptosanguinolentine) has been synthesized in three steps via a new approach starting from commercially available 4-chloroquinoline and 2-chloroaniline. The new methodology consists of two consecutive palladium-catalyzed reactions; a selective Buchwald-Hartwig amination followed by an intramolecular arylation reaction.

Hydrogen uranyl phosphate, HUO/sub 2/PO/sub 4/ /times/ 4H/sub 2/O (HUP), and hydrogen uranyl arsenate, HUO/sub 2/AsO/sub 4/ /times/ 4H/sub 2/O (HUAs), form solid solutions of composition HUO/sub 2/(PO/sub 4/)/sub 1-x/(AsO/sub 4/)x (HUPAs), representing a family of lamellar, luminescent solids that can serve as hosts for intercalation chemistry. The solids are prepared by aqueous precipitation reactions from uranyl nitrate and mixtures of phosphoric and arsenic acids; thermogravimetric analysis indicates that the phases are tetrahydrates, like HUP and HUAs. Powder x-ray diffraction data reveal the HUPAs solids to be single phases whose lattice constants increase with X, in rough accord with Vegard's law Spectral shifts observed for the HUPAs samples. Emission from the solids is efficient (quantum yields of /approximately/ 0.2) and long-lived (lifetimes of /approximately/ 150 /mu/s), although the measured values are uniformly smaller than those of HUP and HUAs; unimolecular radiative and nonradiative rate constants for excited-state decay of /approximately/ 1500 and 5000 s/sup /minus/1/, respectively, have been calculated for the compounds. 18 refs., 5 figs., 2 tabs.

The lamellar solid hydrogen uranyl phosphate can be quantitatively converted to a lamellar hydrate of uranyl phosphage by two routes: an intercalative ion-exchange reaction with aqueous uranium oxide ions and thermal decomposition in an aqueous slurry. An X ray powder pattern of the product can be indexed in tetragonal symmetry with an interlammelar spacing of 11.1 angstrom, expanded from a valve of 8.69 angestrom in hydrogen uranyl phosphate (HUP). Conversion of HUP to UP is accompanied by a drastic diminution in photoluminescence lifetime and intensity. Arrhenius parameters derived from the rates of the intercalation and thermal decomposition reactions indicate that they proceed by quite different mechanisms: the intercalation reaction proceeds with an apparent activation energy, of 12 plus or minus 2 kilo calories/mole and is characterized by a value of 30 plus or minus 2 kilo calories/mole. Samples of UP, obtained by either method, can be converted back to HUP by the action of dilute phosphoric acid in an aqueous slurry at room temperature. Possible mechanisms for these reactions are discussed.

The cycloaddition of α-hydroxy orthoquinodimethane, generated photochemically from 2-methylbenzaldehyde, to the fumarate and acrylate of S-methyl lactate has been found to give a single diastereome...