Olga A. Tarasova

Application of copper catalysis in a one-pot procedure for 1-alkyl-3-methoxy-2-methylthiopyrroles starting from methoxyallene and alkyl isothiocyanates

Abstract 1-Alkyl-3-methoxy-2-methylthiopyrroles are obtained with high purities and in high yields by Cu(I)halide-catalyzed cyclization of the products from addition of 1-lithiomethoxyallene to alkyl isothiocyanates and subsequent methylation.

Synthesis of 2,5-bis(N,N-dialkylamino)thiophenes or 1-alkyl-2-N,N-dialkylamino-5-methylthiopyrroles from propargylic amines and isothiocyanates

Abstract Reaction of lithiated propargylic amines with isothiocyanates, followed by addition of t -BuOK, t -BuOH and methyl iodide gives either 2,5-bis( N,N -dialkylamino)thiophenes or 1-alkyl-2- N,N -dialkylamino-5-methylthiopyrroles depending on the temperature during the treatment with the base.

Synthesis of 3-heteroalkyl-2-N-organylaminothiophenes. The first proof for amino-imino tautomerism of N-monosubstituted aminothiophenes

Abstract The compounds 2-N-methylamino-3-methoxythiophene and 2-N-phenylamino-3-methoxythiophene obtained in fair to good yields in a novel one-pot synthesis from methyl or phenyl isothiocyanate and 1-lithiomethoxyallene have been shown to be in equilibrium with the imino tautomers. The analogous 3-methylthio derivatives obtained by a similar procedure from 1-lithiomethylthiollene exist exclusively in the amino form.

Configurational and conformational analysis of O-vinyl ketoximes by 1H and 13C NMR spectroscopy

1H and 13C chemical shifts and 1H,1H, 13C,1H and 13C,13C coupling constants were determined for a series of O‐vinyl ketoximes. The analysis suggests that O‐vinyl ketoximes are conformationally homogeneous. These exist as a mixture of s‐trans/s‐trans and s‐trans/s‐cis conformers, the former being energetically preferable. The proximity effects for 1H and 13C NMR parameters allow one to detect the stereo‐orientation of asymmetric substituent relatively to the ketoxime moiety. Copyright

Unexpected formation of derivatives of cyclobutene and thiacyclobutane from the reaction between dilithiated benzylacetylene and isothiocyanates

Abstract Reaction of dilithiated benzylacetylene PhCH(Li)-Cue606C-Li with one equivalent of an isothiocyanate RNue605Cue605S followed by successive addition of t-BuOH, a solution of t-BuOK in DMSO and methyl iodide gives exclusively a cyclobutene or a thietane derivative if R=t-Bu or Ph, respectively, and mixtures of the expected thiophene, the cyclobutene and thietane derivatives if R=Me.

ONE-POT SYNTHESES OF 2-N-ALKYLAMINO-, 2-N-PHENYLAMINO-2-N, N-DIALKYLAMINO-, AND 2-N-ALKYL-N-PHENYLAMINOTHIOPHENES

A number of 2-N-alkylamino- or 2-N-phenylamino-, 2-N, N-dialkylamino-, and 2-N-alkyl-N-phenylaminothiophenes have been prepared in good yields by adding a solution of tert-butylalcohol and potassium tert-butoxide in dimethylsulfoxide to a solution of the adduct from a lithiated 1-alkyne, RCH2C≡CLi, or the lithiated allene, tBuCH=C=CHLi, and isothiocyanate, R′N=C=S, in tetrahydrofuran and subsequently hydrolyzing the reaction mixture or quenching it with methyl iodide.

Reaction of Pyrrole Anions with Carbon Disulfide. Synthesis of Pyrrole-3-carbodithioates

Abstract 2,5-Disubstituted pyrroles react with carbon disulfide in the system KOH–DMSO with selective formation of pyrrole-3-carbodithioate anions from which pyrrole-3-carbodithioates were prepared by ethylation in 36–61% yield. From 2-methyl-5-phenyl(2-furyl- or 2-thienyl)pyrroles only pyrrole-3-carbodithioates are formed, with no isomeric pyrrole-4-carbodithioates being present. The reaction direction depends on pyrrole ring substitution: unsubstituted pyrrole selectively forms pyrrole-1-carbodithioate, whereas 2-methyl-, 2,3- and 2,4-dimethylpyrroles give exclusively pyrrole-2-carbodithioates under the same conditions.

The base-catalysed rearrangement of O-propargyl ketoximes to N-1-alkenyl acryl amides

Abstract O -Propargyl ketoximes, available from the reaction of ketoximes with propargyl halides in KOH/DMSO system, readily undergo base-catalysed ( t -BuOK in DMSO or THF) rearrangement to N -(1-alkenyl)acrylamides in 15–58 % yields.

Experimental and theoretical study of the intramolecular C–H···N and C–H···S hydrogen bonding effects in the 1H and 13C NMR spectra of the 2-(alkylsulfanyl)-5-amino-1-vinylpyrroles: a particular state of amine nitrogen

In the 1H NMR spectra of the 1‐vinylpyrroles with amino‐ and alkylsulfanyl groups in 5 and 2 positions, an extraordinarily large difference between resonance positions of the HA and HB terminal methylene protons of the vinyl group is discovered. Also, the one‐bond 1J(Cβ,HB) coupling constant is surprisingly greater than the 1J(Cβ,HA) coupling constant in pyrroles under investigation, while in all known cases, there was a reverse relationship between these coupling constants. These spectral anomalies are substantiated by quantum chemical calculations. The calculations show that the amine nitrogen lone pair is removed from the conjugation with the π‐system of the pyrrole ring so that it is directed toward the HB hydrogen. These factors are favorable to the emergence of the intramolecular C–HB•••N hydrogen bonding in the s‐cis(N) conformation. On the other hand, the spatial proximity of the sulfur to the HB hydrogen provides an opportunity of the intramolecular C–HB•••S hydrogen bonding in the s‐cis(S) conformation. Presence of the hydrogen bond critical points as well as ring critical point for corresponding chelate ring revealed by a quantum theory of atoms in molecules (QTAIM) approach confirms the existence of the weak intramolecular C–H•••N and C–H•••S hydrogen bonding. Therefore, an unusual high‐frequency shift of the HB signal and the increase in the 1J(Cβ,HB) coupling constant can be explained by the effects of hydrogen bonding. Copyright

The first chemoselective synthesis of functionalized 3-vinylpyrroles

Abstract 3-(1-Alkylthio-2-cyano-2-X-ethenyl)pyrroles (X=CN, CONH 2 , CO 2 Et) have been synthesized in 28–58% yields by the reaction of pyrrole-3-carbodithioates with CH-acids (malononitrile, cyanoacetamide, cyanoacetate) in the KOH–DMSO system.