Synthesis and three-dimensional structure of 5,5-disubstituted 2-alkoxy-1,3-dioxanes

It was established by PMR spectroscopy that a chair conformation with an axial orientation of the alkoxy substituent is the primary conformation for 5,5-disubstituted (and unsubstituted) 2-alkoxy-1,3-dioxanes. As compared with alkyl-1,3-dioxanes, 2-alkoxy-1,3-dioxanes are characterized by reversal of the chemical shifts of the axial and equatorial protons attached to C₄, and C₆.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1182–1185, September, 1981.     

Synthesis and some transformations of 5-benzotriazolyl-3,4-dihydropyrid-2-ones

5-(Benzotriazolyl)-substituted 3,4-dihydropyrid-2-ones were obtained by condensation of 4-benzo-triazolyl-5-phenyl(methyl)-5-oxopentanoic acids with benzyl or aryl amines. Dehydrogenation of 3,4-dihydropyrid-2-ones resulted in 5-benzotriazolyl-substituted pyrid-2-ones and/or 5-(phenylamino)pyrid-2-ones, products of nitrogen elimination from the benzotriazolyl substituent. In turn, 5-benzotriazol-1-yl-substituted pyrid-2-ones eliminated nitrogen under Graebe-Ullmann conditions to give indolopyridones.     

Synthesis and transformations of enantiomeric 1,2-disubstituted monoterpene derivatives

Regio- and stereospecific addition of chlorosulfonyl isocyanate to (+)- and (−)-α-pinene 1 resulted in enantiomerically pure β-lactams 2, which were converted to enantiomeric β-amino esters 3 and 1,3-amino alcohols 4 and 6 with ee >99%. The resulting 1,3-difunctional compounds 3, 4 and 6 were transformed to fused saturated 1,3-heterocycles such as tetrahydro-1,3-oxazines 7 and 9, 2,4-pyrimidinedione 11 and 2-thioxopyrimidin-4-one 13 enantiomers.     

Synthesis and some chemical transformations of N-cyclohexyl-2-imino-4-methyl-5,5-pentamethylene-2,5-dihydrofuran-3-carboxamide

Russian Journal of Organic Chemistry -     

Preparation of 1,5-disubstituted pyrrolidin-2-ones

1,5-Disubstituted pyrrolidin-2-ones 18a-g, 19a-h, and 20a-f were synthesized in good to excellent yields via the nucleophilic substitution of 5-(benzotriazol-1-yl)-1-substituted-pyrrolidin-2-ones 9 with allylsilanes, organozinc reagents, and phosphorus compounds. Compounds 9 and 5-(benzotriazol-2-yl)-1-substituted-pyrrolidin-2-one isomers 10 are readily prepared in total 70-84% yields from 2, 5-dimethoxy-2,5-dihydrofuran (7), primary amines 8, and benzotriazole; 9 and 10 react identically with nucleophiles.     

Synthesis of unsymmetrically 2,6-disubstituted 2,3-dihydrothiopyran-4-ones

A series of 2,3-dihydrothiopyran-4-one derivatives with unequal substituents in the 2- and 6-position have been prepared by double conjugate addition of sulfide to enynones. These starting materials were accessed in two steps from terminal alkynes and α,β-unsaturated aldehydes.     

Chiral pyridin-3-ones and pyridines: syntheses of enantiopure 2,4-disubstituted 6-hydroxy-1,6-dihydro-2H-pyridin-3-ones, 2,3-disubstituted 4-iodopyridines, and enantiopure 2,3-disubstituted 4-pyridinemethanols

The development of an innovative method to access enantiopure 2,4-disubstituted 6-hydroxy-1,6-dihydro-2H-pyridin-3-ones starting from D-glucal via the aza-Achmatowicz transformation has been described. These highly functionalized pyridin-3-ones have been utilized for the synthesis of contiguously substituted pyridines through a rapid and efficient Et(3)N/Ac(2)O promoted cyclo-elimination, aromatization cascade, allowing the facile assembly of important pyridine-based building blocks like 2-substituted 3-acetoxy-4-iodopyridines and enantiopure 2-substituted 3-acetoxy-4-pyridinemethanols possessing benzylic stereogenic centers, whose synthesis otherwise would be tedious. The utilization of commercially available sugars as starting materials, mild reaction conditions, catalytic transfer hydrogen (CTH) of α-furfuryl azide derivatives, transfer of chiral aryl/alkyl methanols from enulosides to pyridin-3-ones and pyridines, high yields, and short reaction times are key features of this method. The utility of the method has been further exemplified by demonstrating the usage of the 2-substituted 3-acetoxy-4-iodopyridine for the construction of biologically significant molecules like 2,7-disubstituted furo[2,3-c]pyridines and 7,7'-disubstituted 2,2'-bifuro[2,3-c]pyridines.     

Synthesis of 3-benzoyl- and 3-trichloroacetylimidazolidin-2-ones

Conclusions The reaction of benzoyl and trichloroacetyl isocyanates with ethylenimine was studied and the structure of the obtained adducts was established.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 447–448, February, 1970.     

Synthesis and dynamic stereochemistry of 1,5-disubstituted 2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-2-ones

The 1-isopropyl and 1-benzyl derivatives of 1,5-tetrahydrobenzodiazepin-2-one were synthesized by alkylation under the conditions of phase-transfer catalysis. The inversion of the heterocycle was studied by PMR spectroscopy, and the free energies of activation were determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 254–258, February, 1986.     

Synthesis of 2-aryl-3-hydroxymethyl-5,5-difluoropiperidines

A strategy toward the synthesis of functionalized 5,5-difluoropiperidines, a class of compounds with potential as building block in medicinal chemistry, was developed. In a three-step procedure 2,2-difluoroglutaric anhydride was synthesized starting from ethyl bromodifluoroacetate. This key intermediate reacts fluently with various imines to yield 5,5-difluoropiperidinone carboxylic acids. Subsequent esterification of the obtained carboxylic acids enabled the isolation of trans-substituted 5,5-difluoro-2-arylpiperidinone-3-carboxylates as the major isomers. Reduction of the difluorinated piperidinonecarboxylates using borane gave rise to new trans-2-aryl-1-benzyl-5,5-difluoro-3-hydroxymethylpiperidines in excellent yields.     

Synthesis of 1,5-disubstituted (E)-pent-2-en-4-yn-1-ones

The condensation of 3-arylpropynals with aryl methyl ketones in the presence of sodium hydroxide in 50% aqueous ethanol at 0°C (Claisen-Schmidt reaction) afforded up to 89% of the corresponding (E)-1,5-diarylpent-2-en-4-yn-1-ones. The E configuration of the double C=C bond and cis conformation of the enone fragment in the products in crystal and CDCl₃ solution were determined by X-ray analysis and ¹H NMR spectroscopy.     

Synthesis of 2-substituted isothiazolopyridin-3-ones

The synthesis of some 2-substituted derivatives 1–4 of all four isomeric isothiazolopyridin-3-ones is described. Several novel 1,2-dithiolopyridin-3-ones and 3-thiones were prepared as intermediates.     

Asymmetric synthesis of 1,4-disubstituted 3-methylidenedihydroquinolin-2(1H)-ones

A series of enantiomerically pure or highly enriched (R)- or (S)-3-methylidenetetrahydroquinolin-2-ones was readily prepared by highly diastereoselective Michael additions of various Grignard reagents to quinolin-2(1H)-ones, containing an (R,R)- or (S,S)-di(1-phenylethylamino)phosphoryl group as chiral auxiliary, followed by Horner-Wadsworth-Emmons olefination of formaldehyde. An efficient synthesis of the starting (R,R)- and (S,S)-3-({di[(1-phenylethyl)amino]}phosphoryl)-1-alkyl-quinolin-2(1H)-ones is also described. The relative and absolute configurations of the intermediate adducts and final methylidenequinolinones were established by NMR and X-ray analysis.     

Synthesis and Properties of 3-Substituted 2H-Chromen-2-ones

Russian Journal of Organic Chemistry - The condensation of salicylaldehyde with CH acids [p-methoxyacetoacetanilide, ethyl 3-amino-3-sulfanylidenepropanoate,...