Mikhail A. Kuznetsov

Thermolysis of alk-1-enyl- N-phthalimidoaziridines leads to products of 1,5-electrocyclization of intermediate azomethine ylides with participation of C=C bonds. If acyl or alkoxycarbonyl substituent...

A practical approach to the synthesis of [2‐(trimethylsilyl)ethynyl]pyrazoles was developed through condensation of hydrazines with enynones that are easily accessible frombis(trimethylsilyl)acetylene and arylacetyl chlorides. Optimized conditions for reactions with monoarylhydrazines permit the chemoselective formation of 5‐alkynylpyrazoles in high yields (48–94 %). When monoalkylhydrazines or the parent hydrazine is used, mixtures of 3‐ and 5‐alkynylpyrazoles are formed in 73–79 % yields. The method uses inexpensive starting materials and can be applied to a variety of substrates, which makes it convenient for the synthesis of alkynylpyrazoles.

The thermal reactions of the 2,2,3‐trisubstituted N‐phthalimidoaziridine 1a with dimethyl acetylenedicarboxylate (DMAD), thioketones 4a–4d, and dimethyl azodicarboxylate (5) proceed even at room temperature leading to the five‐membered cycloadducts 2a, 6–8, and 12, respectively, with retention of the spatial arrangement of the aziridine substituents, in contrast to the expectation based on the conservation of orbital symmetry in concerted reactions. The analogous reactions of the tetrasubstituted phthalimidoaziridine 1b with thioketones at 40° lead to the 1,3‐thiazolidine derivatives 10 and 11 as mixtures of diastereoisomers. These unexpected results may be explained by either the isomerization of the intermediate azomethine ylides or a non‐concerted stepwise cycloaddition reaction of these ylides with the dipolarophiles. The structures of some adducts have been determined by X‐ray crystallography.

The oxidation of N-aminophthalimide with lead tetraacetate in the presence of 5-[( E)-2-arylethenyl]-3-(4-methylphenyl)-1,2,4-oxadiazoles and 5-(4-methylphenyl)-3-[ E)-2-phenyl-ethenyl]-1,2,4-oxadiazo...

Oxidative addition of N-aminophthalimide to benzylideneacetone and chalcones followed by thermolysis of the arising 2-aryl-3-acyl-1-phthalimidoaziridines led to the formation of 2,5-disubstituted oxazoles in an overall yield 30–55%. Electron-donor substituents in the aryl fragment of 2-aryl-3-aroyl-1-phthalimidoaziridines accelerate their conversion into oxazoles, and similar substituents in the aroyl fragment retard this process. The possibility was demonstrated of going over to oxazoles from α,β-unsaturated carbonyl compounds via 2-acyl-1-sulfonylaziridines employing chloramine-B. However ethyl 2 cyanocinnamate reacted with chloramine-B with the rupture of the C=C bond and the formation of N-benzylidene-benzenesulfamide.

Thermolysis of dimethyl esters of stereoisomeric phthalimidoaziridine-2,3-dicarboxylic acids in the presence of dimethyl fumarate, dimethyl maleate, and N-phenylmaleimide occurred stereo-specifically...

N‐Amino‐exo‐3,6‐epoxy‐1,2,3,6‐tetrahydrophthalimide is active in the oxidative aminoaziridination reaction toward alkenes substituted with aryl‐, alkyl, and electron‐withdrawing groups, providing access to stable derivatives of N‐aminoaziridine. Yields varied from 19 to 76 %, and trans‐substituted alkenes reacted faster and gave better yields than cis‐alkenes. No products of self‐aziridination were isolated.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)