Reaction of sodium cyanide with 2H-pyran-2-thiones and their 3-bromo derivatives

The reaction of sodium cyanide with 4,5,6-triaryl-2H-pyran-2-thiones and their 3-bromo derivatives led to the formation of 2,5-dihydrothiophenes.     

A novel synthesis of 3-hydroxypiperidin-2-ones via site-selective difunctionalization of piperidine derivatives

An efficient and novel synthesis of 3-hydroxypiperidin-2-ones via site-selective difunctionalization of the inert C(sp³)?H bonds of N-substituted piperidine derivatives is presented. Mechanistically, the formation of the title compounds is believed to go through a cascade process featuring with the sequential formation of cyclic enamine, oxiranium and iminium as key intermediates.     

A novel route to substituted 3-methylidenechroman-2-ones and 3-methylchromen-2-ones

3-Methylidenechroman-2-ones, or their rearrangement products 3-methylchromen-2-ones, were efficiently synthesized by Michael addition of various nucleophiles to 3-diethoxyphosphorylchromen-2-ones followed by Horner-Wadsworth-Emmons reaction of the adducts with formaldehyde. Relative configuration and conformation of the intermediate adducts were studied using NMR spectroscopy and semiempirical PM3 calculations.     

Brominated derivatives of 4-hydroxy- and 4-methoxy-6-methyl-2H-pyran-2-ones

Twenty-five different brominated derivatives of 4-hydroxy-6-methyl-2-pyrone (triacetic acid lactone) and 3-acetyl-4-hydroxy-6-methyl-2-pyrone (dehydroacetic acid) have been prepared. Fifteen derivatives have not been previously described and the preparations of a few known products have been improved. Bromination at C-3, C-5, methyl group at C-6 and deacetylations at C-3 have been the types of reactions used.     

Reaction of dimethylaminomethylenemalonaldehyde bis-N,O-acetal with ketones. A novel route to N-methylpyrroles

Condensation of the bis-N,O-acetal of amethylarrtinomethylenerrzalonaldehyde with ketones, -dimethylaminovinylketones, and -dimethylaminodienones is accompanied by an unusual intramolecular cyclization to give cross conjugated cyclic or acylic ketones containing an N-methyl pyrrole ring in the - or - and'-positions. This is a novel route to substituted pyrroles. Treatment of the bis-N,O-acetal of dimethylaminomethylenemalonaldehyde with 2-(3'-dimethylaminopropen-2'-ylidene)cyclopentanone gave a polyenyl tris-dimethylaminodiketone.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soednenii, No.5, pp. 654–662, May, 1996. Original article submitted February 14, 1996.     

Products from furans. XV. Synthesis of novel tyramine derivatives via 6-hydroxy-2H-pyran-3(6H)-ones

Furan chemistry was utilized for the synthesis of several novel tyramine derivatives. Thus 2H-pyran-3(6H)-ones were used as keystone intermediates for the preparation of novel α,β-disubstituted tyramine derivatives. Furthermore by the same approach tyramine was derivatized with a molecule of GABA.     

Acetyltrimethylsilane: a novel reagent for the transformation of 2H-pyran-2-ones to unsymmetrical biaryls

[reaction: see text] An expeditious synthesis of unsymmetrical biaryls functionalized with electron-withdrawing or -donating substituents is described and illustrated by carbanion-induced ring transformation of 2H-pyran-2-one using acetyltrimethylsilane (ATMS) as a novel reagent in good yield. The novelty of the reaction lies in the creation of an aromatic ring from 2H-pyran-2-ones via two-carbon insertion from ATMS used as a source of carbanion.     

Reaction of β-aeylarylhydrazines with dimethylformamide in the presence of calcium hydride. A novel route to 3-pyrazolin-5-ones

Reaction of β-acylarylhydrazines with calcium hydride in refluxing dimethylformamide (DMF) was found to lead to the formation of 2-aryl-3-pyrazolin-5-ones (V). Application of this novel synthetic method resulted in fair to good yields of a series of 2,4-diaryl-3-pyra7,olin-5-ones. The infrared spectra (potassium bromide) of the products (V) showed that these compounds exist as the laetim tautomer (VI). An oxindole (IIc) was obtained when dimethylbenzamide was substituted for DMF under similar reaction conditions.     

Hydroxy-beta-thiolactams to oxazole-2-thiones. A novel DMSO-promoted oxidation

3-Aryl-3-hydroxy-1-methylazetidine-2-thiones react with HCl in DMSO to give 3-methyl-5-aryloxazole-2-thiones. Substituent effects correlate with rate effects on hydrolyses of acetals of benzaldehyde. An (17)O labeling experiment indicates that the oxygen atom of the product is derived from the hydroxyl group. Trifluoroacetic anhydride/DMSO in CH2Cl2 can also promote the reaction. Mechanisms involving a Grob-type fragmentation of an activated substrate, followed by recyclization, or a cyclopropylcarbinyl type of rearrangement can account for this oxidative rearrangement.     

Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. X. Synthesis of N,N-disubstituted 6-alkyl-4-amino-3,3-dichloro-3,4-dihydro-2H-pyran-2-ones and of 6-alkyl-4-amino-3-chloro-2H-pyran-2-ones

Cycloaddition of dichloroketene to N,N-disubstituted 1-amino-4-methyl-1-penten-3-ones and 1-amino-4,4-dimethyl-1-penten-3-ones occurred in moderate to fair yield only in the case of aromatic N-substitution to give N,N-disubstituted 6-alkyl-4-amino-3,3-dichloro-3,4-dihydro-2H-pyran-2-ones, which were dehydrochlorinated with DBN to afford in good yield N,N-disubstituted 6-alkyl-4-amino-3-chloro-2H-pyran-2-ones. In the case of aliphatic N,N-disubstitution, cyclo-addition led directly to 6-alkyl-4-dialkylamino-3-chloro-2H-pyran-2-ones only for N,N-disubstituted 1-amino-4,4-dimethyl-1-penten-3-ones. The reaction between 1-dimethylamino-4-methyl-1-penten-3-one and dichloroketene gave 3-chloro-4-dimethylamino-3,6-dihydro-6-isopropylidene-2H-pyran-2-one in low yield.     

The synthesis of methyl 2-(benzyloxycarbonyl)amino-3-dimethylaminopropenoate. The synthesis of trisubstituted pyrroles, 3-amino-2H-pyran-2-ones,fused 2H-pyran-2-ones and 4H-pyridin-4-ones

Methyl 2-(benzyloxycarbonyl)aimno-3-dimemylaminopropenoate ( 2 ) was prepared from methyl N-(benzyloxycarbonyl)glycinate ( 1 ) and t-butoxybis(dimethylamino)methane, and used as a reagent for preparation of substituted 3-(benzyloxycarbonyl)amino-4H-quinolizin-4-ones 5 and 6 , ?2H-pyran-2-ones 17–19 , ?2H-1-benzopyran-2-ones 28–31 , and -naphthopyrans 32–35 , ?2H-pyrano[3,2-c]pyridine-2,5-dione 46 , -pyrano-[4,3-b]pyran-2,5-dione 47 , -pyrano[3,2-c]benzopyran-2,5-dione 48 , -pyrano[2,3-c]pyrazol-6-ones 49 and 50 , -pyrano[2,3-d]pyrirnidin-7-ones 51 and 52 derivatives. In the reaction of 2 with 1,3-diketones trisubsti tuted pyrroles 14–16 were formed. Selective removal of benzyloxycarbonyl group was achieved by cat alytic transfer hydrogenation with Pd/C in the presence of cyclohexene to afford free 3-amino compounds 7 , 8 , 20 , 36–38 and 53–57 in yields better than 80%.     

4- And 5-hydroxylaminothiazolidine-2-thiones. Rearrangement of the carbamoyl derivatives to 4- and 5-ureidothiazolidin-2-ones

The carbamoylation of 4- and 5-hydroxyaminothiazolidine-2-thiones by methyl and 3,4-dichlorophenyl isocyanates leads to the corresponding hydroxyureas, which rearrange to 4- and 5-ureidothiazolidin-2-ones on heating in the presence of a base. Under these conditions, the hydroxyurea based on 5-hydroxylaminothiazolidin-2-one is converted to 5-ureidooxazolidin-2-one.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1678–1682, December, 1987.     

Vibrational spectra of piperidine,pyrrolidine, morpholine,and their n-methyl derivatives adsorbed on aerosil silica

The i.r. and Raman spectra of piperidine, pyrrolidine, morpholine, their N-methyl derivatives were obtained for the adsorbed state, aqueous solution, and liquid state. It was suggested that these molecules form hydrogen bonds with surface silanols. The existence of ND stretching band on the deuterated silica suggested that the hydrogen bonds were formed between N atoms and silanols.     

2-aminothiophenes from triacetonamine: A convenient way to novel sterically hindered piperidine derivatives

Bicyclic 2-aminothiophenes 2, which are available by the Gewald reaction of 2,2,6,6-tetramethyl-4-piperidone (triacetonamine, 1), were employed in cyclizations to give new tricyclic thienopyridine and thienopyrimidine derivatives, without protection of the piperidine nitrogen, whereas methylation of 2 occurred exclusively at the piperidine nitrogen. Acylation of 2 in the presence of a tertiary amine yielded N-thienyl imides, due to the high NH acidity of the intermediate N-thienyl amides. Similarly, benzylation of an N-thienyl amide proceeded readily in sodium ethoxide solution. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:529–536, 1998     

Reactions of 4-Hydroxy-2H-pyran-2-ones with Some N-Nucleophiles

Russian Journal of General Chemistry -     

A simple route to morpholine derivatives via copper-acetylide addition to carbodiimide in the presence of oxiranes

A novel catalytic multicomponent reaction for the synthesis of morpholine derivatives has been reported. The reactions involve terminal alkynes, carbodiimides, and oxiranes using [Cu (CH₃CN)₄]PF₆, ^tBuOLi, and TBPAc in anhydrous NMP. Aryl and heteroaromatic terminal alkynes were tolerated. Carbodiimides could be symmetrical and unsymmetrical substrates with aryl or alkyl substituents. The reaction exhibited a good regioselectivity when unsymmetrical carbodiimides were employed.     

Preparation and reactions of 3,4-dihydro-2H-pyran-2-ones

The Michael reaction of ethyl cinnamates with deoxybenzoin gave ethyl 3,4,5-triaryl-5-oxopentanoates which were hydrolysed to the corresponding acids. The latter could be cyclized to the respective 3,4-dihydro-2H-pyran-2-ones which underwent ring opening with several nucleophiles to the corresponding acid derivatives. However, their reaction with ammonium acetate led to the formation of 3,4-dihydro-2-pyridones. The 3,4-dihydro-2-pyrones and pyridones were dehydrogenated to the corresponding 2-pyrones and 2-pyridones by fusion with sulfur.     

Microwave-mediated reactions of 3-aminomethylpyridines with acetylenedicarboxylates. A novel synthetic route to dihydronaphthyridines and naphthyridine-1-ones

Reaction of 3-(1-alkylamino)pyridines with electron deficient acetylenes in the presence of acids yields 1,2-dihydro[2,7]naphthyridine-3,4-dialkyldicarboxylates 4 in 35-72% yield. Compounds 4 unsubstituted in position 1 can be easily oxidized with potassium permanganate into the respective naphthyridine-1-ones derivatives 5 in good yields.