Enolether, XIII. Die Acylierung von Enolethern mit reaktiven Carbonsäure-chloriden

A New Method for the Synthesis of 3-Thiocyanatopyrazolo[1,5-a]pyrimidines

In this article, we demonstrate how an original effective "metal-free" and "chromatography-free" route for the synthesis of 3-thiocyanatopyrazolo[1,5-a]pyrimidines has been developed. It is based on electrooxidative (anodic) C-H thiocyanation of 5-aminopyrazoles by thiocyanate ion leading to 4-thiocyanato-5-aminopyrazoles (stage 1, yields up to 87%) following by their chemical condensation with 1,3-dicarbonyl compounds or their derivatives (stage 2, yields up to 96%). This method is equally effective for the synthesis of 3-thiocyanatopyrazolo[1,5-a]pyrimidines, both without substituents and with various donor (acceptor) substituents in the pyrimidine ring.

New 2-(aryl/heteroaryl)-6-(morpholin-4-yl/pyrrolidin-1-yl)-(4-trifluoromethyl)quinolines: synthesis via Buchwald–Hartwig amination, photophysics, and biomolecular binding properties

New 6-(morpholino/pyrrolidino)quinolines displaying interesting photophysical and biomolecular binding properties achieved by Buchwald–Hartwig amination.

Synthesis of tetra-substituted 5-trifluoromethylpyrazoles via sequential halogenation/palladium-catalyzed C–C and C–N cross-coupling

The assembly of tetra-substituted 5-trifluoromethylpyrazoles is presented, involving palladium-catalyzed Negishi or Buchwald–Hartwig cross-couplings to install carbon or nitrogen-based 4-substituents.

General pathway for a convenient one-pot synthesis of trifluoromethyl-containing 2-amino-7-alkyl(aryl/heteroaryl)-1,8-naphthyridines and fused cycloalkane analogues

A convenient and general method for the synthesis in 26-73% yields of a new series of 7-alkyl(aryl/heteroaryl)-2-amino-5-trifluoromethyl-1,8-naphthyridines from direct cyclocondensation reactions of 4-alkoxy-1,1,1-trifluoroalk-3-en-2-ones [CF₃C(O)CH=C(R¹)OR, where R¹ = H, Me, Ph, 4-MePh, 4-OMePh, 4-FPh, 4-BrPh, 4-NO₂Ph, 2-furyl, 2-thienyl and R = Me, Et] with 2,6-diaminopyridine (2,6-DAP), under mild conditions, is described. Another synthetic route also allowed the synthesis of 2-amino-5-trifluoromethyl-cycloalka[b][1,8]naphthyridines in 33-36% yields, from direct or indirect cyclo-condensation reactions of five-, six- and seven-membered 2-trifluoroacetyl-1-methoxy-cycloalkenes with 2,6-DAP.

Synthesis and RT inhibitory activity evaluation of new pyrimidine-based seco-nucleosides

Eleven new 3',4'-seco acyclic nucleosides (4-14) were prepared by nucleophilic substitution of protected pyrimidine bases on ethyl 3,3-diethoxypropanoate (3). Structures were characterized spectroscopically and a brief analysis of their conformation in solution was performed by the vicinal coupling constants (3)JH2'aH3' and (3)JH2'bH3'. In solid state, compound 6 forms a homodimer linked by hydrogen bonding. In preliminary tests all compounds show low toxicity and gentle activity against HIV-1 RT in vitro.

Fluorinated acyclo-C-nucleoside analogues from glycals in two steps

A convenient two-step strategy is reported for the synthesis of fluorinated optically pure acyclo-C-nucleoside analogues starting from simple glycals. In the first step, benzyl- or p-methoxybenzyl-protected glycals are treated with trifluoroacetic anhydride, bromodifluoroacetyl chloride, trichloroacetyl chloride, and perfluorooctanoyl chloride, respectively, in the presence of Et3N. This one-pot procedure yields 1,2-unsaturated sugars (1,5-anhydro-3,4,6-tri-O-benzyl (or p-methoxybenzyl) 2-deoxy-2-perhalogenoacyl-D-arabino / lyxo-hex-1-enitols 4-9) acylated at C-2. In the second step, a selective ring transformation is induced by treatment of the C-acylated glycals with bis-nucleophiles (hydrazine, phenylhydrazine, o-phenylenediamine, hydroxylamine). In particular, 1,5-anhydro-3,4,6-tri-O-benzyl-2-deoxy-2-trifluoroacetyl-D-arabino-hex-1-enitol (4) and 1,5-anhydro-2-deoxy-2-trifluoroacetyl-3,4,6-tri-O-(p-methoxybenzyl)-D-arabino-hex-1-enitol (8) were reacted with these nucleophiles generating the final C-nucleoside analogues of pyrazole (10, 11, and 12), diazepine (13), and isoxazole (15), respectively, containing a carbohydrate side chain linked to the heterocyclic ring.

Synthesis and structure of new trichloromethyl-β-diketones — 5-Trichloromethylisoxazole and 5-isoxazolecarboxylic acid derivatives

An improved method for the synthesis of a new series of trichloromethyl-β-diketones including 1,1,1-trichloropentan-2,4-dione (2a), 1,1,1-trichloro-3-methylhexan-2,4-dione (2b), 4,4,4-trichloro-1-phenylbutan-1,3-dione (2c), 4,4,4-trichloro-2-methyl-1-phenylbutan-1,3-dione (2d), 2-trichloroacetylcyclohexanone (2e), 4-tert-butylcyclohexanone (2f), 4-tert-butylcycloheptanone (2g), and 4-tert-butylcyclooctanone (2h) is reported. A multinuclear NMR study showed that β-dicarbonyl compounds 2b and 2d–2h are predominantly in the keto form and 2a and 2c are in the enol form. The trichloromethyl-β-diketones react with hydroxylamine hydrochloride leading to three sets of isoxazole derivatives.Key words: acetals, acylation, trichloromethyl-1,3-diketones, 2-trichloroacetylcycloalkanones, isoxazoles, cyclocondensation.

New entry to a three-component pyrimidine synthesis by TMS-Ynones via Sonogashira coupling

[reaction: see text] TMS-ynones are versatile synthetic equivalents of beta-keto aldehydes and can be readily synthesized in an atom-economical fashion by coupling (het)aroyl chlorides and (TMS)-acetylene with only one equiv (!) of triethylamine under Sonogashira conditions. This mild ynone synthesis is also a suitable entry to 2,4-disubstituted pyrimidines in the sense of a one-pot three-component reaction, i.e., a coupling-addition-cyclocondensation sequence.