Vladimir I. Tyvorskii

New synthetic route to the alkaloid withasomnine by ring transformation of a functionalized cyclopropanol via the parent pyrrolo[1,2-b]pyrazole

Abstract Withasomnine has been prepared by rearrangement of 1-(3-chloropropyl)-cyclopropanol into 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazole, followed by bromination and [NiCl 2 (dppp)]-catalyzed phenylation.

New synthetic approaches to 2-perfluoroalkyl-4H-pyran-4-ones

Abstract A convenient synthesis of 5-substituted 2-perfluoroalkyl-4H-pyran-4-ones by dehydration of 2,3-dihydro-3-hydroxy-6-perfluoroalkyl-4H-pyran-4-ones is described. The 6-substituted and parent 2-perfluoroalkyl-4H-pyran-4-ones have been more successfully prepared using the condensation of alkyl enol ethers, derived from β-dicarbonyl compounds, with ethyl perfluoroalkanoates.

Synthesis of 3-(Trifluoromethyl)benzo[c][1,6]naphthyridines from Substituted 4H-Pyran-4-ones via 4-Amino-5-Aryl-2-(trifluoromethyl)pyridines

Abstract The cyclization of acylated 4-amino-5-aryl-2-(trifluoromethyl)pyridines under the action of P 2 O 5 /POCl 3 smoothly afforded 3-(trifluoromethyl)benzo[ c ][1,6]naphthyridines in good yields. Intermediate aminopyridines were synthesized in a two-step sequence from the corresponding 4 H -pyran-4-ones, which were prepared by reaction of 2-acetyl-2-aryloxiranes and 4-dimethylamino-3-(4-methoxyphenyl)-3-buten-2-one with ethyl trifluoroacetate under basic conditions.

Synthesis of 5-alkyl-4-amino-2-(trifluoromethyl)pyridines and their transformation into trifluoromethylated 1H-pyrazolo[4,3-c]pyridines

Abstract 5-Alkyl-4-amino-2-(trifluoromethyl)pyridines were prepared in good yields starting from the corresponding pyridinols either using condensation with tosyl isocyanate or by alkylation with 2-chloroacetamide and subsequent Smiles type rearrangement. The cyclisation of diazonium salts, generated from 5-alkyl-4-amino-2-(trifluoromethyl)pyridines, afforded trifluoromethylated 1H-pyrazolo[4,3-c]pyridines.

A convenient approach to the synthesis of 2-(2-aminoethyl)pyrroles and their heterocyclization into hydrogenated pyrrolopyridines and related pyrroloindolizines

Abstract 2-(2-Aminoethyl)pyrroles and 2-(2-succinimidoethyl)pyrroles were prepared from acetals of ethyl 4-oxoalkanoates via latent vinyl 1,4-dicarbonyl compounds as the key intermediates. The Pictet–Spengler condensation of 2-(2-aminoethyl)pyrroles with aromatic aldehydes gave 4,5,6,7-tetrahydro-1 H -pyrrolo[3,2- c ]pyridines in good yields. 4,5,7,8,9,9a-Hexahydro-3 H -pyrrolo[2,3- g ]indolizines were prepared in a similar way starting from 2-(2-succinimidoethyl)pyrroles.

A convenient synthesis of 3-functionalized 5-alkoxymethyl- and 5-phenoxymethyl-2(5H)-furanones and their transformations into related epoxy and methylene lactones

Abstract A convenient procedure for the preparation of 3-functionalized 5-alkoxymethyl- and 5-phenoxymethyl-2(5H)-furanones is described. The method is based on the condensation of various β-alkoxy- or β-phenoxy-α-hydroxy ketones with β-activated esters in the presence of catalytic amounts of sodium methoxide. Results are reported showing the possible transformations of these 2(5H)-furanones into related epoxy and α-methylene lactones.

Regiospecific synthesis of α-diones, α,α-dialkoxyketones and α-alkoxy-α-sulfenylated ketones

Abstract A convenient synthesis of α-diones and their monoprotected acetals, i.e. α-ketoacetals, was developed by mercury induced solvolysis of regiospecifically formed α-chloro-α-(alkylthio)ketones. Analogously, α-alkoxy-α-sulfenylated ketones were formed when reacting α-chloro-α-sulfenylated ketones with an alkaline alcoholic medium. α-Alkoxy-α-sulfenylated ketones themselves could be transformed into α-diones or α-ketoacetals, which in turn were hydrolyzed under anhydrous conditions into the corresponding α-diones.