T. V. Mikhalina

Reaction of 2-chloro-3-(4-N,N-dimethylaminoanilino)-1,4-naphthoquinone with cyclic amines (piperidine, morpholine, and pyrrolidine)

It was shown that the reaction of 2-chloro-3-(4-N,N-dimethylaminoanilino)-1,4-naphthoquinone with piperidine in the absence of a solvent gives not only a product of replacement of the chlorine atom by a piperidino group, 3-(4-N,N-dimethylaminoanilino)-2-piperidino-1,4-naphthoquinone, but also 2-(4-N,N-dimethylaminoanilino)-1,4-naphthoquinone and 2-(4-N,N-dimethylaminoanilino-2-piperidino)-1,4-naphthoquinone. The latter compounds are the only reaction products formed in dimethyl sulfoxide. The reaction with morpholine occurs in a similar way, whereas that with pyrrolidine gives only a product of replacement of the chlorine atom by hydrogen.

A combinatorially convenient version of synthesis of 5-substituted oxazole-4-carboxylic acid ethyl esters

Reaction of ethyl isocyanoacetic acid with sodium hydride in anhydrous benzene, followed by treatment with carboxylic acid chlorides or N-(acyloxy)pyrrolidine-2,5-diones, gives 5-substituted oxazole-4-carboxylic acid esters. The procedure is applicable to derivatives of various carboxylic acids, including saturated aliphatic, α,β-unsaturated, alicyclic, aromatic, heterocyclic, and N-Boc-protected amino acids.

The interaction of 2-(4-acetylphenylamino)-3-piperidino-1,4-naphthoquinone with hydroxylamine and hydrazines

With acid catalysts 2-(4′-acetylphenylamino)-3-piperidino-1,4-naphthoquinone reacts with hydroxylamine and aryl hydrazines exclusively at the carbonyl group of its side chain. The products corresponding to the condensation at the naphthoquinone C=O group could not be detected.

A straightforward and convenient synthesis of Cbz-protected 2-(1-aminoalkyl)oxazole-5-carboxylates

Cbz-protected 2-(l-aminoalkyl)oxazole-5-carboxylates are readily obtainable by a two-step enantioselective sequence involving reaction of benzyloxycarbonyl protected amino acids with α-chloro-β-ketoesters and subsequent cyclization of the resulting acyloxyketones to required oxazoles upon treatment with neat ammonium trifluoacetate.

Fluorinated 1,3\lambda^{4}\delta^{2},2,4 -benzodithiadiazines : a synthetic, structural and theoretical study

The series of title compounds has been prepared through both electrophilic (C6HnF5−n−N=S=N−SiMe3 + SCl2) and nucleophilic (C6HF4−S−N=S=N−SiMe3 + CsF) intramolecular ortho-cyclisation reactions, and the former route seems to be the more effective. High regioselectivity of the ring-closing procedures is observed in both cases. The compounds were characterised by X-ray crystallography and multinuclear (1H, 13C, 15N and 19F) NMR spectroscopy. In accordance with GIAO calculations, 15N{1H} experiments and the effects observed on complete substitution of hydrogen by fluorine, the high-field signal in the 15N NMR spectra can be assigned to N-4 and the low-field signal to N-2. In the crystal, 5,6,7-trifluoro- (5) and 5,6,8-trifluoro-1,3λ4δ2,2,4-benzodithiadiazine (6) are planar, whereas the 6,8-difluoro derivative 3 is bent along the S1···N4 line by 8.3°. According to NICS calculations the heterocycle moiety in this compound class is antiaromatic while the carbocycle is aromatic. The fluorine substituents increase the aromaticity − and in some cases (especially when a fluorine atom is present in the 8-position) the antiaromaticity − of the corresponding rings. The ortho-fluoro-containing starting material C6HnF5−n−N=S=N−SiMe3 (n = 2: 10) cyclises to the fluorinated 2,1,3-benzothiadiazole 27 upon treatment with CsF instead of SCl2. For starting compound 6-HC6F4−S−N=S=N−SiMe3 (14) the planar (Z,E) configuration features a short intramolecular H···N contact, as evidenced by X-ray diffraction. Both the reaction pathways mentioned are also discussed. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2003)