Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XXIII: Deformation of the piperidine ring in some bicyclic compounds possessing a bridgehead amide nitrogen atom

Some bridgehead nitrogen compounds possessing the CH(Me)-bridgehead N? C(O) system have been synthesised and their configurations assigned. The chemical shifts of the proton geminal to the methyl group provides evidence for the existence of a deformed chair conformation for the methyl substituted ring.     

Synthesis of imidazolidinone containing an ammonium nitrogen atom in the ring

The reaction of 1-(2,2-dimethoxyethyl)-1,3,3-trimethylurea with 2-methylresorcinol in dioxane in the presence of trifluoromethanesulfonic acid affords a new type of imidazolidin-2-ones, viz., 5-(2,4-dihydroxy-3-methylphenyl)-1,1,3-trimethyl-2-oxoimidazolidinium triflate containing an endocyclic ammonium nitrogen atom.     

Strain-induced regioselectivities in reactions of benzyne possessing a fused four-membered ring

[reaction: see text] A fused four-membered ring has a powerful directing ability in effecting the regioselective reactions of benzyne with ketene silyl acetal, nucleophile, and alpha-alkoxyfuran.     

Nitrosoalkylureas with a quaternary nitrogen atom

Conclusions The selectivity of the nitrosation of cholinelike alkylureas is explained in terms of the theory of boundary orbitals.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 369–371, February, 1985.     

Sulfur participation in solvolysis involving four-membered ring intermediates

Neighboring group participation via four-membered ring intermediates resulting in complete rearrangement occurs in the methanolysis of R₁R₂C(SCH₂C₆H₅)CH₂CH(R₃)OTs when R₁=R₂=R₃=Me and when R₁=R₂=Me, R₃=H. No rearrangement is found for R₁=R₂=R₃=H or R₁=R₂=H, R₃=Me. The case of R₁=Me, R₂=R₃=H is intermediate.     

TBHP-mediated oxidative thiolation of an sp3 C-H bond adjacent to a nitrogen atom in an amide

The first example of molecular sieve-promoted TBHP-mediated direct oxidative thiolation of an sp(3) C-H bond adjacent to a nitrogen atom with disulfides under metal-free conditions, which allows for preparation of numerous S,N-containing compounds, is presented. Moreover, diverse benzothiazoles and a fipronil analog can be synthesized through this strategy.     

Nickel-catalyzed reaction of butadiene with strained ring olefins: Formation of a four-membered cyclic compound

Reaction of butadiene with strained ring olefins such as norbornene, dicyclopentadiene etc. Gives an exo-methylene- and methyl-substituted four-membered cyclic compound (II). The effective catalysts are (n-Bu₃P)₂NiBr₂/NaBH₄ or /alkoxide $\text{1}\text{1}$ syn-π-crotylbis(triethyl phosphite)nickel hexafluorophosphate (IV), and tetrakis(triethyl phosphite)nickel/CF₃COOH $\text{1}\text{1}$. π-Crotyl complex IV reacts with the strained ring olefins to give the corresponding product similarly. It is concluded that the active species for this catalytic reaction is a nickel hydride and that this reaction proceeds through π-crotyl intermediate.     

Pyrolytic desulfurization ring contraction of condensed thiadiazines as a general route towards pyrazoloazines and pyrazoloazoles with a bridgehead (ring junction) nitrogen atom

Pyrolytic conversion of [1,2,4]triazino[3,4-b][1,3,4]thiadiazin-4-ones, [1,3,4]thiadiazino[2,3-b]quinazolin-10-ones and [1,2,4]triazolo[3,4-b][1,3,4]thiadiazines into their corresponding pyrazolo[5,1-c][1,2,4]triazin-4-ones, pyrazolo[4,3-b]quinazolin-9-ones and pyrazolo[5,1-b][1,2,4]triazoles via desulfurization ring contraction is described. The starting condensed 1,3,4-thiadiazines were prepared from the corresponding readily available 4-amino-3-thioxo-1,2,4-triazin-5(4H)-ones, 3-amino-2,3-dihydro-2-thioxoquinazolin-4(1H)-one and 4-amino-3(2H)-thioxo-1,2,4-triazoles upon reaction with the appropriate α-haloketones in two steps, or directly in one step in ethylpyridinium tetrafluoroborate (ionic liquid, IL).     

The structure and energies of some unsaturated four-membered ring carbocycles

A number of cyclobutane derivatives containing one or more double bonds in endo- or exocyclic positions have been studied by the molecular mechanics method within the context of the MM2 force field. Generally speaking, the structures and energies of these compounds are well calculated in cases in which they are known experimentally and are predicted in others. Examples are shown of the use of the moments of inertia of molecules, which are known from microwave studies, in conjunction with molecular mechanics calculations to yield better structures than could be obtained by either method alone. Compounds examined include cyclobutene, methylenecyclobutane, Dewar benzene, and related compounds.     

Condensed heterocyclic systems with a quaternary nitrogen atom

Nitro and amino derivatives of pyrido[1,2-f]phenanthridinium perchlorate were synthesized by the Pschorr method and by photocyclodehydrogenation from N-(nitrophenyl)-or N-(aminophenyl)pyridinium perchlorates. The mechanism of the photoconversion was investigated.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1226–1229, September, 1978.     

Mesoionic compounds with a bridged nitrogen atom.

The cyclization of (4-quinazolinylthio)phenylacetic and acetic acids gives extremely reactive thiazolo[3,2-c]quinazolinium 3-oxides, which, depending on the structure of the mesoionic ring, react with either electrophilic or nucleophilic reagents.See [1] for Communication 16.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 408–412, March, 1989.     

Pyrolysis of four-membered ring molecules studied by microwave spectroscopy

Very low pressure vapor phase pyrolysis (flash thermolysis) of four-membered ring compounds was followed by microwave spectroscopic detection of the reaction products. The molecules studied included substituted cyclobutanes, thietanes, oxetane and azetidine. Microwave spectroscopy is well suited not only to observe stable reaction products but also to detect unstable species formed during pyrolysis. The investigation provided a wealth of information on typical decomposition patterns during pyrolysis of four-membered ring compounds. In addition, new methods were found for producing some unstable molecules with improved efficiency.