Long-range 4J coupling constants and conformation of the four-membered heterocycles

The correlation between the puckering angle of the four-membered cycle and ⁴J has been obtained from analysis of the PMR spectra of some 2-substituted azetidines and oxetanes. The absolute values of ⁴J_cis and ⁴J_trans were found to decrease with decreasing of the puckering angle.     

Reactions of alkylenebisbromomalonates with nucleophiles

Treatment of alkylenebisbromomalonates with nucleophiles (AcOK, AgOH, KHCO₃, 1,8-diazabicyclo[5.4.0]undec-7-ene, or Ph₃P) results mainly in their debromination to give cycloalkane-1,1,2,2-tetracarboxylates. When H₂O and acids are present, the reaction gives products of the substitution of one or two bromine atoms by hydrogen. Alkaline hydrolysis results in oxacycloalkane-α,α,α′,α′-tetracarboxylic acids. The reaction mechanism is discussed.     

Sterically hindered inversion of nitrogen atoms in cyclic hydrazines:N,N′-dialkyl-1,3,4-oxadiazolidines; 1,3,4-thiadiazolidine; and 4,5-benzo-1,2,3,6-tetrahydropyridazine

N,N′-Diisopropyl-substituted 1,3,4-oxadiazolidine3c, 1,3,4-thiadiazolidine6, 4,5-benzo-1,2,3,6-tetrahydropyridazine8, and new 3,4-dialkyl-1,3,4-oxadiazolidines9–14 were synthesized and studied. The configurational stability of the N atoms does not change on going from compound3c to itsS-analog6 and decreases in the case of pyridazine8. 3,4-Di-tert-alkyl-1,3,4-oxadiazolidines3d and11–14 were found to be promising objectes for optical resolution.     

Structure of products of the reaction of 2-cyanoaziridine with carbonyl compounds

The structure of azimexone (3), the product of the reaction of 2-cyanoaziridine with acetone, was confirmed on the basis of¹H and¹³C NMR spectra. The formation of this product is accounted for by the -aziridinoalkylating action of an intermediate containing a good leaving iminoyloxy group. Similar reactions were observed for 1-chloromethylaziridine and a 1-aziridinylmethylammonium salt (6), but not for 1-methoxymethylaziridine (7) and 1-aziridinemethanol.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2136–2139, December, 1993.     

Mass spectrometry of organic compounds of the group V Elements: VI—A new type of amine fragmentation under electron impact

A new type of amine fragmentation under electron impact is elucidated for proline, sarcosine and aspartic acid derivatives and aminomethylphosphines of the general formula R₂NCH₂X. Ordinary α-cleavage affording the \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm R}_2 \mathop {\rm N}\limits^{\rm + } {\rm = CH}_{\rm 2} $\end{document} ion is suppressed by elimination of a neutral HX particle and [M - HX]⁺ ion formation, or M-HX neutral particle ejection and generation of an [HX]⁺ ion from [M]⁺˙. Such fragmentation is ensured by the presence of an α-heteroatom (N, O, P, S) in one substituent (X) and a CO₂R type delocalizing group in the α-position of the other substituent (R₂N).     

A novel bicyclic system, 1,6-diaza-3,8-dioxabicyclo[4.4.1]undecane

Condensation of monoethanolamine with formaldehyde affords 1,6-diaza-3,8-dioxabicyclo[4.4.1]undecane andN,N-methylene-bis(oxazolidine) in a ratio of 18.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 342–343, February, 1994.     

Autoassembly of cage structures

Complete autoassembly of dilactones4–6 from dihydroxytetraesters of the type X₂YC(CH₂) _n CYX₂ (X = CO₂R, Y = OH,n = 2, 3) was performed in high yields under the conditions of acid or base catalysis. The classic syntheses of the Tröger's base, Meerwein ester, and dilactams were considered from the viewpoint of bicycle autoassembly.     

Autoassembly of cage structures

Thed,l-(1a) andmeso-forms (1b) of α,α'-dihydroxy-α,α'-dimethyladipic acid, dilactone (3), diiminodilactone (4), and lactonolactam (5) were obtained by the reaction of acetonylacetone with KCN and HCl. The transformations of1 to the esters2, dilactone3 to la, and diiminodilactone4 to dilactone3 were studied. It was shown that3 can be readily obtained from la by thermolysis, acid catalysis, and DCC action as well as by acid catalyzed cyclization of2a, while dilactone3 can be obtained from1b and2b in negligible yield only under drastic conditions, obviously, due to the partial epimirization of themeso-forms. The mild thermolysis of1b leads totrans-lactonoacid (6), from which the ester7 has been obtained. The effective acid catalyzed cyclization of amides8 and9 to3, lactamoamide12 to5, and amide14 to model lactone13 was found. The NMR spectra of the products were studied, and a¹H NMR test was suggested for identification ofd,l- andmeso-forms1 and2. The stereochemistry of monolactones6, 7, 9, 10a, 10b, 11, and dilactone3 was established. The differences in the chemical behavior of α,α'-dihydroxyglutaric and adipic acids were explained by the significant reduction of the non-bonded interactions of the substituents in the corresponding monolactones during the transfer from 1,3- to 1,4-substituted systems.