Jurij Svete

Regioselective 1,3-Dipolar Cycloadditions of (1Z)-1-(Arylmethylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide Azomethine Imines to Acetylenic Dipolarophiles

The 5,5-dimethylpyrazolidin-3-one (4), prepared from ethyl 3-methylbut-2-enoate (3) and hydrazine hydrate, was treated with various substituted benzaldehydes 5a – i to give the corresponding (1Z)-1-(arylmethylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide azomethine imines 6a – i. The 1,3-dipolar cycloaddition reactions of azomethine imines 6a – h with dimethyl acetylenedicarboxylate (=dimethyl but-2-ynedioate; 7) afforded the corresponding dimethyl pyrazolo[1,2-a]pyrazoledicarboxylates 8a – h, while by cycloaddition of 6 with methyl propiolate (=methyl prop-2-ynoate; 9), regioisomeric methyl pyrazolo[1,2-a]pyrazolemonocarboxylates 10 and 11 were obtained. The regioselectivity of cycloadditions of azomethine imines 6a – i with methyl propiolate (9) was influenced by the substituents on the aryl residue. Thus, azomethine imines 6a – e derived from benzaldehydes 5a – e with a single substituent or without a substituent at the ortho-positions in the aryl residue, led to mixtures of regioisomers 10a – e and 11a – e. Azomethine imines 6f – i derived from 2,6-disubstituted benzaldehydes 5f – i gave single regioisomers 10f – i.

A simple synthesis of aplysinopsin analogues by dimethylamine substitution in N,N-(dimethylamino)methylidene derivatives of five-membered heterocycles

Abstract Some new aplysinopsin analogues were prepared by a simple coupling of N , N -(dimethylamino)methylidene substituted hydantoin, thiohydantoin, and thiazolone derivatives, with indole derivatives. Configuration around the exocyclic CC double bond was determined on the basis of long-range heteronuclear coupling constants using 2D HMBC correlation technique.

Stereoselective synthesis of (1R,3R,4R)-3-(1,2,4-triazolo[4,3-x]azin-3-yl)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones

Abstract (1R,3R,4R)-3-(1,2,4-Triazolo[4,3-x]azin-3-yl)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-ones were prepared in 68–94% d.e. in three steps from (1R)-(+)-camphor via coupling of (1R,4R)-3-[(E)-(dimethylamino)methylidene]-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one with hydrazinoazines followed by oxidative cyclisation of the intermediate hydrazones with methanolic bromine. The structures were determined by 2D NMR techniques and NOESY spectroscopy as well as by X-ray diffraction.

Copper(I) Iodide-Catalyzed Cycloadditions of (1Z,4R*,5R*)-4-Benzamido-5-phenylpyrazolidin-3-on-1-azomethine Imines to Ethyl Propiolate

Regioselective copper(i) iodide-catalyzed cycloadditions of chiral pyrazolidin-3-on-1-azomethine imines 3a–j to ethyl propiolate 4 gave cycloadducts 5a–h and 5′i and 5/5′j as single regioisomers. In terms of facial selectivity, cycloadducts 5a–h and 5′i were obtained as single diastereomers, whereas the reaction of dipole 3j was less selective and gave a mixture of 5j and 5′j in a ratio of 15:85. Stereoselectivity of copper(i) iodide-catalyzed cycloadditions of ethyl propiolate 4 to azomethine imines 3 was controlled by the stereodirecting phenyl group at position 5 and by the ortho-substituents at the 1′–Ar residue.

Preparation of Polysubstituted Isochromanes by Addition of ortho-Lithiated Aryloxiranes to Enaminones

The reaction of ortho-lithiated aryloxiranes with various enaminones straightforwardly affords new functionalized isochromanes as mixtures of two epimeric stereoisomers in reasonable to very good yields (50-90%). The two diastereomers, which show a high structural variability, can be easily separated by column chromatography.

1,3-Dipolar Cycloadditions to (5Z)-1-Acyl-5-(cyanomethylidene)- imidazolidine-2,4-diones: Synthesis and Transformations of Spirohydantoin Derivatives

Cycloadditions of various 1,3-dipoles to (5Z)-1-acyl-5-(cyanomethylidene)-3-methylimidazolidine-2,4-diones 8 or 9, prepared in 3 steps from hydantoin (1) (Schemes 1 and 2), were studied. In all cases, reactions proceeded regio- and stereoselectively. The type of product depended on the 1,3-dipole and/or dipolarophile employed as well as on reaction conditions. Thus, with stable dipoles under neutral conditions, spirohydantoin derivatives 12 – 16 were obtained (Scheme 2), while under basic or acidic conditions, pyrazole- or isoxazole-5-carboxamides 18 and 23 – 26 and carboxylate 27 were formed via aromatization of the newly formed dihydroazole ring, followed by the simultaneous cleavage of the hydantoin ring (Schemes 3 – 5).

Parallel synthesis of 7-heteroaryl-pyrazolo[1,5-a]pyrimidine-3-carboxamides

A simple and practical four-step protocol for the parallel synthesis of 7-heteroaryl-pyrazolo[1,5-

Synthesis of 3-(α- and β-d-arabinofuranosyl)-6-chloro-1,2,4-triazolo[4,3-b]pyridazine

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