Arnold T. Nielsen

Synthesis of polyazapolycyclic caged polynitramines

Abstract Syntheses of new polyazapolycyclic caged polynitramines are described. Sequentially reacting 4,10-dibenzyl-2,6,8,12-tetraacetyl-2,4,6,8,10,12-hexaazaisowurtzitane (5a) with NOBF4 and NO2BF4 in sulfolane solvent produces 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo-[5.5.0.05,9.03,11]dodecane, 6). Syntheses of two new polyazapolycyclic caged trinitramines, 3,5,12-trinitro-3,5,12-triazawurtzitane (7a) and 2,4,10-trinitro-2,4,10-triazaadamantane (12a), as well as their labile parent secondary amines, are discussed. A new caged polynitrosamine, 3,5,12-trinitroso-3,5,12-triazawurtzitane (7d), has been obtained by ring-cleavage nitrosation of the new hexamine-wurtzitane compound 3,5,7,9-tetraazahexacyclo-[9.3.1.13,7.02,9.04,13.05,10]-hexadecane (10).

Intramolecular reactions of nitroolefin-β-diketone Michael adducts : Formation of 3-oxo-2,3-dihydro-4H-1,2-benzoxazine and 4(5H)-benzofuranone derivatives

Abstract 1,3-Cyclohexanedione (3) undergoes Michael addition to β-nitrostyrene in methanolic sodium methoxide to form 3,5-dioxo-4-phenyl-2,3,5,6,7,8-hexahydro-4H-1,2-benzoxazine (5a). With 1-nitropropene 3 forms the corresponding 4-methyl derivative (5b). These substances had been designated as 4-substituted 5-oxo-5,6,7,8-tetrahydro-4H-1,2-benzoxazine-2-oxides (4a, b) by other workers. 5,5-Dimethyl-1,3-cyclohexanedione (9) under similar conditions adds to β-nitrostyrene to form 2-(2-nitro-1-phenylethyl)-5,5-dimethyl-1,3-cyclohexanedione (10); 9 and 2-nitro-1-phenylpropene yield 3-phenyl-2,6,6-trimethyl-6,7-dihydro-4(5H)-benzofuranone (12). In other reactions various β-diketones add to nitroolefins to yield normal Michael adducts, 4-nitro-1-alkanones (1, 2). Molecular ion fragmentation patterns and mechanisms of formation of the abnormal addition products are presented and their rationalizations discussed.

Intramolecular reactions of nitro-olefin–cyclohexane-1,3-dione Michael adducts. Crystal structure of 3-(4-bromophenyl)-6,7-dihydro-2-hydroxyiminobenzofuran-4(5H)-one

Cyclohexane-1,3-dione and its 5,5-dimethyl derivative (dimedone), in contrast to other β-diketones, behave abnormally in Michael additions to nitro-olefins. From nitro-olefins RCHCH·NO2(R = alkyl or aryl, not H) 3-substituted 6,7-dihydro-2-hydroxyiminobenzofuran-4(5H)-ones can be prepared. These compounds are the first known butenolide derivatives having a 2-hydroxyimino-substituent. 3-(4-Bromophenyl)-6,7-dihydro-2-hydroxyiminobenzofuran-4(5H)-one has been prepared from cyclohexane-1,3-dione and 4-bromo-β-nitrostyrene and resolved into pure syn- and anti-forms. The structures of both forms have been established from n.m.r. spectra, and by X-ray crystallography from diffractometer data. Single crystals of a 1 : 2 mixture of syn- and anti-forms (VIIA and B; anti: syn= 2 : 1) are orthorhombic with space-group Pbca, cell dimensions a= 17·37, b= 7·89, and c= 19·76 A. The crystals were found to be disordered because they contain a mixture of syn- and anti-forms of the oxime. Three possible ways of describing the mixture of syn- and anti-forms were refined by full-matrix least-squares of 805 statistically significant reflections to weighted R values of 0·051, 0·056, and 0·073. None of the three refinements gave good agreement with bond distances previously reported for CN an N–OH in oxime structures (although mean values for the 0·051 and 0·057 refinements did). The observed apparent planarity of the cyclohexenone ring is attributed to the presence of equal amounts of both ring-inversion isomers in the crystalline state. Short intermolecular distances of 2·63 and 2·84 A between the oxygen of both syn- and anti-oxime groups and the ketonic oxygens give strong evidence for intermolecular hydrogen bonding.

Formation and crystal structure of 3-(4-bromophenyl)-2-hydroxyimino-6,7-dihydro-4(5H)-benzofuranone. Michael addition of cyclohexane-1,3-dione to 4-bromo-ω-nitrostyrene

The structure of the abnormal Michael adduct named in the title has been established by spectra and X-ray crystallography.

The 2,4-dibenzylidenecyclobutanone anion: a unique intermediate leading to 2,4-dibenzylidenecyclobutanone dimer

The title non-classical enolate anion is involved in a base-catalysed reaction leading to a dimer, C36H28O2, whose structure has been established.