Yu. I. El'natanov

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.

Reactions of N-, P-, S-, and As-nucleophiles with cyanoacetylene

Conclusions1.High trans-stereospecificity has been shown in the addition to cyanoacetylene of: a) secondary aliphatic amines, with cooling, and b) under the usual conditions with sterically hindered amines, phosphines, mercaptan, and arsine, and also with amines with reduced positive mesomeric capacity of the nitrogen atom.2.The cis-products of the addition to cyanoacetylene of aziridines, diaziridine, imidazole, di-tert-butylamine, phosphines, and arsine are highly resistant to cis-trans isomerization. In cis-β-di-tert-butylaminoacrylonitrile, amide-type conjugation is sterically hindered.

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 1∶8.

Determination of configuration of products of nucleophilic addition to activated acetylenes by the NMR method

ConclusionsIt was shown that the stereospecificity of SSCC3C,Htrans > 3JC,Hcis is applicable as a configurational test for di- and trisubstituted alkenes R2E(Y)C=C(X)H with various heteroatomic substituents (E=N, P, S) and activating groups (X=CO2Alk, CN at Y=H, and X=Y=CO2Alk, CN, CF3).

Reactions of N-, P-, and S-nucleophiles with methyl propiolate

Conclusions1.In contrast to the case of cyanoacetylene, the nucleophilic addition to methyl propiolate takes place with the preferential or exclusive formation of trans products, if steri cally hindered N-nucleophiles and N-, P-, S-nucleophiles with a weakened +M-effect of the central heteroatom are used.2.For the qualitative evaluation of the stereochemical result of the nucleophilic addition reaction to activated acetylenes, it was proposed to use the σR constant of the activating substituent.

Autoassembly of cage structures: 9. Complete autoassembly of dilactones of ?,??-dihydroxy-?,??-dialkoxycarbonyladipic and -pimelic acids

Complete autoassembly of dilactones4–6 from dihydroxytetraesters of the type X2YC(CH2)nCYX2 (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 Trögers base, Meerwein ester, and dilactams were considered from the viewpoint of bicycle autoassembly.

Autoassembling of cage structures

Treatment of alkylenebismalonates with NaH and benzoyl peroxide afforded dibenzoyloxy derivatives. Alkaline hydrolysis of the latter gave alkylenebistartronic acids. Tetramethyl and tetraethyl esters and tetraamides of these acids were synthesized

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.

Reactions of aziridine, its dimer, 2,2-dimethyl-aziridine dimer, and β,β-bis-N-aziridinoethylamine with aromatic aldehydes and dialdehydes

The reactions of aziridine, its dimer, 2,2-dimethylaziridine dimer, and the novel compound β,β-bis-N-aziridinoethylamine with aromatic aldehydes and dialdehydes have given novel compounds.

INVESTIGATION OF THE STEREOCHEMISTRY OF N-SUBSTITUTED 2,5-DIMETHYL-4-PIPERIDINONES BY NMR-SPECTROSCOPY

The conformations of the cis and trans isomers of N-substituted 2,5-dimethyl-4-piperidinones were studied by means of the1H and13C NMR parameters. It was established that in the case of bulky and electron-acceptor substituents attached to the N atom the cis isomers are virtually completely represented by the chair (2a,5e) conformation, while the trans isomers are characterized by the chair (2e,5e) ⇄ twistboat (2a,5e) ⇄ chair (2a,5a) conformational equilibrium. It is demonstrated that 1-tert-butyltrans-2,5-dimethyl-4-piperidinone hydrochloride has the twist (2a,5e) conformation.