Andrey A. Tolmachev

Bicyclic Conformationally Restricted Diamines

CONTENTS

“Reported, but Still Unknown.” A Closer Look into 3,4-Bis- and 3,4,5-Tris(trifluoromethyl)pyrazoles

Straightforward practical synthetic approaches to 3,4-bis- and 3,4,5-tris(trifluoromethyl)pyrazoles have been developed. The key step of the both syntheses is a transformation of the carboxylic group in a pyrazole core into the trifluoromethyl group by sulfur tetrafluoride. The elaborated synthetic protocols allow gram-scale preparation of the target products. The obtained compounds are comprehensively characterized by means of crystallographic analysis, determination of pK(a) values and fluorescence measurements.

3-Haloquinolines by Friedländer Reaction of α-Haloketones

A general approach to 3-fluoro-, 3-chloro-, and 3-bromoquinolines which relies on organosilane-promoted Friedländer reaction of α-haloketones is described. The scope of the methylene component as well as influence of the organosilane component on the outcome of the reaction is studied. The method can be used under parallel synthesis conditions.

Synthesis of Quinolines from 3-Formylchromone

A facile and versatile procedure for the synthesis of 3-(2-hydroxybenzoyl)quinolines and 7H-chromeno[3,2-c]quinolin-7-ones was elaborated on the basis of TMSCl-mediated recyclization of 3-formylchromone with various anilines. Limitations and scope of this methodology were established, and a possible mechanism for the heterocyclizations was proposed.

Aminoheterocycles as synthons for combinatorial Biginelli reactions

Chlorotrimethylsilane (TMSCl) has been utilized as an efficient promoter and water scavenger in the synthesis of diverse dihydropyrimidines via Biginelli type MCR-heterocyclization using aminoheterocycles. High yields and a simple workup of target compounds enable the facile generation of combinatorial libraries comprising more than 2,000 compounds of high structural and functional diversity. A representative set of 89 compounds is described.

Approach to the library of fused pyridine-4-carboxylic acids by Combes-type reaction of acyl pyruvates and electron-rich amino heterocycles.

A library of fused pyridine-4-carboxylic acids (including pyrazolo[3,4-b]pyridines, isoxazolo[5,4-b]pyridines, furo[2,3-b]pyridines, thieno[2,3-b]pyridines, and pyrido[2,3-d]pyrimidines) was generated by Combes-type reaction of acyl pyruvates and electron-rich amino heterocycles followed by hydrolysis of the ester. The library members were also demonstrated to undergo the standard combinatorial transformations including amide coupling and esterification, as well as less common heterocyclizations to 1,2,4-triazoles and 1,2,4-oxadiazoles.

Tungsten pentacarbonyl as a potential protecting group for soft lewis base centres in alkylation of multifunctional molecules

Abstract Reaction of W(CO) 6 or (PhNH 2 )W(CO) 5 with the molecules which possess both diphenylphosphanyl- and dialkylamino group or nitrogen — containing hetcrocyclic ring proceeds selectively through “soft” Lewis base groups and can be used for the protection of the groups from alkylalion. As a rule, the diphenylphosphanyl group participates in the co-ordination, but in some cases an sp 2 -hybridized nitrogen was shown to be the preferable co-ordination site. The new synthesized compounds have been characterized by NMR, IR spcctroscopy, and elemental analysis.

An entry into hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives.

Hexahydro-2H-thieno[2,3-c]pyrrole is proposed as a low molecular weight polar scaffold to construct compound libraries used in the search for new drugs. Practical syntheses of derivatives of this bicyclic scaffold were developed, based on [3 + 2] cycloaddition of the ylide generated from N-benzyl-1-methoxy-N-((trimethylsilyl)methyl)methanamine and 4-substituted 2,3-dihydrothiophene 1,1-dioxides. All of the 3-substituted hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives were obtained as single diastereomers. Conformational properties of the hexahydro-2H-thieno[2,3-c]pyrrole 1,1-dioxide derivatives were explored using X-ray diffraction studies. The potential of the scaffold to generate libraries of 3D-shaped molecules was demonstrated.

Sulfonyl Fluorides as Alternative to Sulfonyl Chlorides in Parallel Synthesis of Aliphatic Sulfonamides

Two types of aliphatic sulfonyl halides (Cl versus F) were compared in parallel synthesis of sulfonamides derived from aliphatic amines. Aliphatic sulfonyl fluorides showed good results with amines bearing an additional functionality, while the corresponding chlorides failed. Both sulfonyl halides were effective in the reactions with amines having an easily accessible amino group. Aliphatic sulfonyl chlorides reacted efficiently with amines bearing sterically hindered amino group while the corresponding fluorides showed low activity.

Dry HCl in Parallel Synthesis of Fused Pyrimidin-4-ones

The parallel solution-phase synthesis of substituted thieno[2,3- d]pyrimidin-6-carboxylic acids has been accomplished. This strategy relies on a cyclization of 2-aminothiophen-3,5-dicarboxylates with a set of nitriles, followed by hydrolysis to construct the library of corresponding acids. The convenient procedure for use and dosage of dry HCl for the reaction was elaborated and adapted for semiautomated solution-phase parallel synthesis. With the use of another (hetero)aromatic ortho-aminocarboxylate, mini-libraries of diverse fused pyrimidin-4-ones were synthesized. The scope and limitations of the approach are discussed.