Development of a Novel Approach to Formation of a Pyrrole Ring: Synthesis of 2,3,5-Substituted 1-[2-(Vinyloxy)ethyl]pyrroles

Reaction of 2-(vinyloxy)ethylisothiocyanate with unsaturated carbanions generated in situ from propargyl ethers and amines when treated with superbases, after S-alkylation and cyclization of the adducts in the presence of CuBr, leads to the previously unknown 2,3,5-substituted 1-[2-(vinyloxy)ethyl]pyrroles.     

Stereoisomerism of N-(1-Propenyl)thiobenzamide

A prototropic rearrangement of N-prop-2-enylbenzocarbothioamide afforded two stereoisomeric N-prop-1-enylbenzocarbothioamides (IIa, b) isolated as individual compounds. The stereoisomerism is due to hindered rotation around thioamide bond C(S)-N and also to -diastereoisomerism. The configuration of the isolated isomers was investigated by IR spectroscopy, AM1 and PM3 methods. In the molecules occurs the p,-conjugation with participation of nitrogen atom and multiple bonds resulting in formation of a united delocalized MO in the planar fragment C(S)-NC = C.     

N,N′-bis(2-Vinyloxyethyl)carbodiimide

Previously unreported N,N-bis(2-vlnyloxyethyl)carbodiimide was synthesized by the reaction of N,N -bis(2-vinyloxyethyl)thiourea with yellow mercuric oxide in CH₂Cl₂ at room temperature.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1897–1898, August, 1990.     

Vinyl Ethers Containing an Epoxy Group: XXI. Synthesis and Acid-Catalyzed Cyclization of 1-[ω-(Vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanols- A Simple Route to 2-Propynyloxymethyl-Substituted Cyclic Polyethers

Base-catalyzed reaction of 2-[-(vinyloxy)alkoxy]methyloxiranes with 2-propynyl alcohol (3 wt % of t-BuOK, 60-85°C, 3-12 h) afforded first reperesentatives of the 1-[-(vinyloxy)alkoxy]-3-(2-propynyloxy)-2-propanol series in up to 99% yield. Treatment of 1-[2-(vinyloxy)ethoxy]- and 1-[2-(vinyloxy)ethoxyethoxy]-3-(2-propynyloxy)-2-propanols with trifluoroacetic acid (0.5 wt. %) in dry diethyl ether resulted in cyclization with formation of up to 96% of (2-methyl-1,3,6-trioxocan-4-yl)methyl- and (2-methyl-1,3,6,9-tetraoxacycloundecan-4-yl)methyl 2-propynyl ethers.     

Mass Spectra of New Functionally Substituted Heterocycles: V. First Example of McLafferty Rearrangement in the Series of 5-(1-Ethoxyethoxy)-2,3-dihydropyridines and 3-(1-Ethoxyethoxy)pyridines Derived from α-Lithiated 1-(1-Ethoxyethoxy)allene and Methoxymethyl Isothiocyanate

Previously unknown 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-dihydropyridine, 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine, and 2-methylsulfanylpyridin-3-ol were synthesized from α-lithiated 1-(1-ethoxyethoxy)allene, methoxymethyl isothiocyanate, and methyl iodide, and their fragmentation under electron impact was studied. At ionizing electron energies of 12 and 60 eV in the temperature range from 50 to 250°C, the molecular ions derived from 5-(1-ethoxyethoxy)-2-methoxy-6-methylsulfanyl-2,3-dihydropyridine and 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine decompose along two main pathways: rupture of the C-O bond in the acetal moiety to give oxonium ions with m/z 73 (in the two cases) and 168 (pyridine derivative) and unexpectedly facile McLafferty rearrangement with elimination of ethoxyethene molecule to produce fragment ions with m/z 173 and 141, respectively. The latter pathway was not observed previously for dihydropyridines and acetals, and it predominates in the fragmentation of 3-(1-ethoxyethoxy)-2-methylsulfanylpyridine. Expulsion of methanol molecule from the molecular ion of 5-(1-ethoxyethoxy)-2-methoxy-6- methylsulfanyl-2,3-dihydropyridine occurred only above 170°C.     

Reactions of heterocumulenes with organometallic reagents: XIII. Quantum-chemical study on the mechanisms of syn -( Z )/ anti -( E )-isomerization of methyl 2-methoxy- N -methylbuta-2,3-dienimidothioate

Mechanisms of syn-(Z)/anti-(E) isomerization of methyl 2-methoxy-N-methylbuta-2,3-dienimidothioate, including rotational, inversion, promoted by N-protonation, and nucleophile-catalyzed, were studied by quantum-chemical methods, and the corresponding thermodynamic and kinetic parameters were calculated. The most probable mechanisms of isomerization of buta-2,3-dienimidothioates were found to be inversion (E _a = 74.4 kJ/mol) and nucleophile-catalyzed (E _a = 61.6 kJ/mol). Original Russian Text ? V.A. Shagun, N.A. Nedolya, 2007, published in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 11, pp. 1591–1600. For communication XII, see [1].     

Reactions of Heterocumulenes with Organometallic Reagents: X. Quantum-Chemical Study of the Reaction of Aliphatic Isothiocyanates with Lithiated Allenes. Intramolecular Rearrangements of 1,3,4-Azatrienes

Study of the potential energy surface for the reaction of isothiocyanates with -lithiated allenes showed that the formation of 1,3,4-azatriene occurs in one step through a four-center transition state. [1,5]-Sigmatropic rearrangements of 1,3,4-azatrienes and electrocyclizations of the resulting conjugated 1,3,5-azatriene systems lead to formation of dihydropyridine ring. Pyrrole structures are more likely to arise from protonation of 3-alkoxy-1,3,4-azatriene.