Synthesis of aminonicotinonitriles and diaminopyridines through base-catalyzed ring transformation of 2H-pyran-2-ones

An efficient and convenient synthesis of 2-amino-6-aryl-4-methylsulfanylnicotinonitriles (2), 2-amino-6-aryl-4-substituted-aminonicotinonitriles (4), and 2-amino-6-aryl-4-substituted-aminopyridines (6) has been delineated and illustrated through base-catalyzed ring transformation of 6-aryl-3-cyano-4-methylsulfanyl/substituted-amino-2H-pyran-2-ones (1, 3, and 5) with cyanamide and ammonium carbonate separately.     

Tandem reaction of 3-hydroxyhexa-4,5-allenic esters: a novel access to diversely substituted 2H-pyran-2-ones and indenes

A highly efficient synthesis of diversely substituted 2H-pyran-2-ones and indenes through Br?nsted acid promoted tandem reaction of the readily obtainable 3-hydroxyhexa-4,5-allenic esters under extremely mild conditions has been developed.     

Reaction of piperidine and morpholine with 2H-pyran-2-ones, 2H-thiopyran-2-ones, 2H-pyran-2-thiones,and 2H-thiopyran-2-thiones. A novel route to thiophene derivatives

The reaction of piperidine or morpholine with 2H-pyran-2-ones was found to give open chain δ-oxoamides, while with 2H-thiopyran-2-ones, thiophene derivatives were formed. For 2H-pyran-2-thiones, either open chain δ-oxothioamides or thiophene derivatives were obtained. From the ¹ H nmr data of the pyran derivatives, the effect of the replacement of ring and carbonyl oxygens with sulphur on the chemical shift of the H-3 proton could be studied.     

A regioselective palladium-free protocol for accessing unsymmetrical biaryls through ring transformation of 6-aryl-α-pyrones

A regioselective synthesis of unsymmetrical biaryls with electron withdrawing or donating substituents is described and illustrated by carbanion-induced ring transformation of 6-aryl-α-pyrones with methoxyacetone in excellent yield. Our methodology is an alternative to classical organometal-catalyzed aryl-aryl coupling reactions and can be applied to the synthesis of functionally demanding naphthyl biaryls for the development of new ligands for asymmetric synthesis.     

Studies of a proposed mechanism for the reaction between 2H-pyran-2-ones and organomagnesium compounds

Part of the reaction between 2H-pyran-2-ones and organomagnesium compounds has been investigated by means of MNDO and ab initio calculations. Criteria for the mechanism of reaction are provided by the stereoselectivity observed and calculations are consistent with this stereoselectivity. Conformations of the reaction intermediates are given.     

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.     

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

Russian Journal of General Chemistry -     

Oxidative cyclization of beta-hydroxyenones with palladium(II): a novel entry to 2,3-dihydro-4H-pyran-4-ones

[reaction: see text] A palladium(II)-mediated oxidative cyclization was found to be effective for the preparation of structurally diverse 2,3-dihydro-4H-pyran-4-ones from the corresponding beta-hydroxyenones. Attractive features of this transformation include the ready availability of the starting enones, the regiocontrol, and the easy access of enantiopure 2,3-dihydro-4H-pyran-4-one from the corresponding enantiopure enone.     

A synthesis of carbasugar-sugar pseudodisaccharides via a cycloaddition-cycloreversion reaction of 2H-pyran-2-ones

Cycloaddition of 3-carbomethoxy-2H-pyran-2-one to a vinylated sugar followed by the loss of bridging CO(2) from the cycloadduct affords a cyclohexadiene which can be manipulated to a carbasugar-sugar pseudodisaccharide.     

A novel NHC-catalyzed transformation of 2H-chromene-3-carboxaldehydes to 3-methyl-2H-chromen-2-ones

An unexpected transformation of 2H-chromene-3-carboxaldehydes to coumarin derivatives, mediated by NHC, is reported.     

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%.     

Stereochemistry of the bucherer-bergs reaction and a modified strecker reaction on tetrahydro-2H-pyran-3-ones

The stereochemical aspects of the Bucherer-Bergs reaction and a modified Strecker reaction on tetrahydro-2H-pyran-3-one derivatives have been studied in details through the use of several nmr techniques. It was found that, in both reactions, the orientation of the substituents introduced on C-3 of the pyran ring, depends from the number and nature of the substituents on the neighbouring C-2 atom.     

Remarkable O(2)-effect in 1,4-additions of diethylzinc to 6-acyloxy-2H-pyran-3(6H)-ones and 6-alkoxy-2H-pyran-3(6H)-ones

Under the influence of air, a facile 1,4-addition of diethylzinc to acyloxypyranones and alkoxypyranones 1 takes place. Reaction of diethylzinc with molecular oxygen provides EtOOZnEt, which catalyzes the addition of diethylzinc.     

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.     

Desulfinylative Pd-catalyzed coupling reaction of arenediazonium salt with aryl sulfinates to give unsymmetrical biaryls

An efficient route for the synthesis of unsymmetrical biaryls was developed via palladium catalyzed reaction of arenediazonium salts and aryl sulfinates under inert atmosphere. This synthesis involves cascade processes. Tetrabutylammonium iodide was used as an iodide source for in situ formation of aryl iodide, followed by desulfinylative cross-coupling reaction between aryl sulfinates and aryl iodides. A wide range of biaryls were selectively prepared in one pot from simple substrates in good to excellent yields.     

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.