Том 54, № 7 (2018)

The system hydrogen peroxide–hexafluoroacetone sesquihydrate effectively oxidizes adamantane in the presence of VO(acac)₂ to afford 64% of adamantan-1-ol in tert-butyl alcohol or 76% of adamantan-2-one in a mixture of acetic acid with pyridine.

Reactions of di- and trichlorocyclopentenones with adamantan-1-amine, 1-(adamantan-1-yl)ethanamine, and amino acids (histidine, L-proline, L-methionine methyl ester hydrochloride) afforded the corresponding enamino ketones.

The condensation of naphthalen-2-amine with furan-2-carbonyl chloride in propan-2-ol gave N-(naphthalen-2-yl)furan-2-carboxamide which was treated with excess P₂S₅ in anhydrous toluene to obtain the corresponding thioamide. The oxidation of the latter with potassium hexacyanoferrate(III) in alkaline medium afforded 2-(furan-2-yl)naphtho[2,1-d][1,3]thiazole. A probable mechanism of its formation was proposed, and the ring closure involving C¹ of the naphthalene fragment was substantiated by quantum chemical calculations. Electrophilic substitution reactions of 2-(furan-2-yl)naphtho[2,1-d][1,3]thiazole (nitration, bromination, formylation, and acylation) involved exclusively the 5-position of the furan ring.

The use of zinc in Barbier-type reactions of (2R,3R)-3-[(1R)-1-{[tert-butyl(dimethyl)silyl]oxy}-ethyl]-4-oxoazetidin-2-yl acetates with halogen derivatives led to the formation of expected substitution products. The reaction of the title compound with a reagent prepared from samarium powder, a catalytic amount of iodine, and methyl 2-bromopropanoate in THF gave an anomalous substitution product, methyl 2-{(2S,3S)-3-[(1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl]-4-oxoazetidin-2-yl}-2(R,S)-methyl-3-oxopentanoate. Alkylation of the latter with methyl bromoacetate afforded methyl 2-{(2S,3S)-3-[(1R)-1-{[tert-butyl(dimethyl) silyl]oxy}ethyl]-1-(2-methoxy-2-oxoethyl)-4-oxoazetidin-2-yl}-2(RS)-methyl-3-oxopentanoate which underwent fragmentation through cleavage of the N¹–C⁴ bond under the action of sodium bis(trimethylsilyl)-amide in THF at–78°C. The resulting acyclic amide, dimethyl {(2R,S,3Z)-2-[(1R)-1-{[tert-butyl(dimethyl)-silyl]oxy}ethyl)]-4-methyl-5-oxohept-3-enoylamino}malonate, was smoothly converted to new functionalized N-substituted pyrrolidinones via intramolecular Michael type cyclization in methylene chloride in the presence of NEt₃–DMAP–Boc₂O.

Efficient methods have been developed for regioselective synthesis of new organochalcogen compounds containing 2,3-dihydro-1-benzofuran-2-ylmethyl and 7-methyl-2,3-dihydro-1-benzofuran-2-ylmethyl substituents by reactions of selenium and sulfur dichlorides and tellurium tetrachloride with 2-allylphenol and 2-allyl-6-methylphenol.

3,3-Diphenyl-3H-pyrazoles containing an electron-withdrawing substituent in the 5-position undergo van Alphen–Hüttel rearrangement with migration of one phenyl group to C⁴ on heating in an aprotic solvent (benzene, toluene), as well as on keeping at 20°C in acetic acid in the presence of a catalytic amount of concentrated sulfuric acid. Under similar conditions, 3,3-diphenyl-3H-pyrazoles with a strong electronwithdrawing group (sulfo or cyano) on C⁴ isomerize to 1H-pyrazoles via migration of one phenyl group to N². If a moderate electron-withdrawing substituent (alkoxycarbonyl or acetyl group) is present in the 4-position, the acid-catalyzed phenyl group migration is directed mainly to the C⁴ atom, while thermal migration, toward N². Probable reasons for the observed similarity and differences in the regioselectivities of the thermal and acidcatalyzed van Alphen–Hüttel rearrangements have been proposed.

While developing methods of synthesis of sulfolanes fused through the C³–C⁴ bond to oxazolidin-2- one and morpholin-2-one fragments, the reactivity of cis- and trans-isomeric amino alcohols of the sulfolane series toward a number of cyclizing agents was studied. The cis isomers reacted with dimethyl acetylenedicarboxylate and triphosgene to afford the corresponding morpholin-2-ones and oxazolidin-2-ones, whereas the trans isomers gave rise to open-chain aminofumarates and urea derivatives, respectively. The reactions of both cis- and trans-amino alcohols with oxalic acid derivatives (diethyl oxalate, oxalyl chloride) led to the formation of exclusively acyclic mono- and/or diamides.

The structure of 5,5-bis(bromomethyl)-2-(4-methoxyphenyl)-1,3-dioxane has been studied by ¹H and ¹³C NMR and X-ray diffraction. Molecules of the title compound exist in the chair conformation with equatorial orientation of the methoxyphenyl substituent. The dioxane ring inversion path, free conformational energy, and optimal conformation of the aryl group have been determined by computer simulation in terms of the DFT PBE/3ζ method. The calculation results are consistent with the X-ray diffraction data.

A one-pot procedure has been developed for the synthesis of 2,7-diaryl(hetaryl)-4,9-dimethylperhydro- 2,3a,5a,7,8a,10a-hexaazapyrenes by cyclocondensation of aren(hetaren)amines with formaldehyde and 2,6-dimethyl-1,4,5,8-tetraazadecalin in the presence of YbCl₃ · 6 H₂O as catalyst.

The alkylating activity of N-allyl- and N-propargyltriflimides toward N,N′-dicyclohexyl- and N,N′-diphenylcarbodiimides has been studied. Activation of the nitrogen atom by two electron-withdrawing trifluoromethanesulfonyl groups favors cleavage of the C–N bond in the absence of a catalyst with the formation of N-substituted unsaturated ureas.

The reaction of 5,5-disubstituted 4-methyl-3-phenyl-2,5-dihydrofuran-2-imines with phenyl isothiocyanate afforded N-[5,5-disubstituted-4-methyl-3-phenylfuran-2(5H)-ylidene]-N′-phenylthioureas.