Band 57, Heft 4

Five hydroxyethyl-2-tetrazenes (1 - 5) and their methyl ethers (6 - 10) have been synthesized and hydrogen bonding in these compounds has been investigated by theoretical and spectroscopic (IR, 1 H NMR, 15 N NMR) methods. The structure of 1,1,4,4-tetrakis(2-hydroxyethyl)- 2-tetrazene (4) was determined byX-ray diffraction analysis. Several conformationswith intramolecular hydrogen bonds were investigated by ab initio B3LYP as well as semiempirical SCF calculations. In all cases, conformers with OH- - -N hydrogen bonds with azo nitrogen atoms as acceptors (conformers A, B, C) are found as most stable. Incompounds with small or flexible N 1 - and N 4 -substituents R besides the hydroxyethyl group (3, 4), hydrogen bonds forming six-membered rings, with the R groups taking syn positions at the N 1 -N 2 and N 3 -N 4 bonds (conformer A), are preferred over those with seven-membered rings and R taking anti positions (conformer B). Steric interaction in the other compounds (1, 2, 5) leads to destabilization of conformers A and conformers B become more stable. A special case is presented by compound 4 which has only hydroxyethyl substituents on the 2-tetrazene unit. In the most stable conformer (4C) there are two OH- - -O and one OH- - -N hydrogen bonds. By IR solution measurements intra- and intermolecular hydrogen bonds could be distinguished. Association shifts Δδ measured by 1 H NMR spectroscopy, indicate that the investigated compounds exhibit comparable association properties with intermolecular association clearly prevailing. 15 N NMR spectra of compounds 1 - 10 in two solvents have been measured if solubility was sufficient. The data indicate that all nitrogen atoms of 1 - 5 participate in H bonding. In the crystalline state, molecules 4 adopt a conformation without intramolecular H bonds (4D) and are associated by intermolecular OH- - -O hydrogen bonds that form a three-dimensional network. An untypical decomposition pattern was discovered for benzyl derivatives 5 and 10.

Novel rearrangements of 3-ylidene-piperazine-2,5-dione (1) were achieved affording Cope rearrangement products 3 and 4 under neutral conditions or tricyclic piperazine-2,5-diones 5, rac-6 and 7 by additional tandem cyclisation in formic acid. Cope rearrangement products 3 and 4 were transformed into new quaternary α-amino acids 9 and 11 by hydrogenation and hydrolysis.

The stable hydroperoxides rac-cis-2a,d and 4a,c were synthesized by oxidation of the salts 1. The 3-hydroxy sultims rac-cis-3a,b and sultams 5a,e were obtained by reduction of the corresponding hydroperoxides 2 and 4. Crystal structure analyses were performed for compounds 3b, 4a, 5a, 5e and revealed a variety of intermolecular contacts leading to cyclodimers, tetramers and polymers. In carboxylic esters 4a and 5a, cyclodimers with a 20- or 22-membered ring are formed via ‘head-to-tail’ CO⋯H-O hydrogen bonds and π/π-interactions, without participation of the SO 2 group. The 1,1-dioxide 4c, which has no carbonyl substituent, forms a tetrameric unit by combining two symmetry independent molecules through strong OO-H⋯O-S-O and short nonclassical O-S-O⋯H-C hydrogen bonds. The sultam 1,1-dioxide 5e, bearing a highly substituted 2-phenyl ring, exhibits in the solid state strong intermolecular O-S-O⋯H-O hydrogen bonds and forms the first polymer chain in this cyclic sulfonamide series. In sultims 2a, 3a and 3b, but not in 2d, strong intermolecular S-O⋯H-O hydrogen bonds are observed and polymer chains originate from the c-glide plane (space group P2 1 /c)in 2a and from two symmetry independent molecules in 3a. In the 1-oxide 2d a ‘head-to-head’ dimer was found with two strong SO⋯H-OO hydrogen bonds in a 14- or 16-membered ring. Short nonclassical C-H⋯O-C interactions connect the dimers to form polymeric chains.

Fast atom bombardment (FAB) has been used for mass spectrometric characterization of oligomeric cyanines and squaraines of the indole series which are linked by different aromatic spacers. Markedly different results were obtained for the oligomers and for the corresponding monomers. In addition to the expected mono-anions and mono-cations, ions of high relative abundance were detected which can only be explained on the basis of FAB-induced chemical reactions of the initial oligomers. Formation of allenes, hydrogenation and dehydrogenation, respectively, is characteristic for this class of compounds under FAB-conditions.

The orthoamide derivatives 1s and 2e were prepared from the guanidinium salt 7a and the appropriate carbanions. Cleavage of the orthoamide 2e with benzoyl chloride affords the amidinium salt 10a, which can be transformed into the amidinium salt 10b by an anion exchange reaction. The enamines 11a-i, 12a-c, 13a, b, 14a-c, 15a, b, 16, 17a, b, 18a, b, 19a, b, 20 were prepared by condensation of CH 2 -acidic compounds with the carboxylic acid orthoamides 2a-j. The orthoamide 2d reacts with 1-nitropropane to give the amidinium salt 27a which is transformed into the salt 27b. From benzyl cyanide and orthoamides 2g, i the enamines 30 and 32 were obtained. Similar condensation reactions were performed with the orthoamides of alkyne carboxylic acids 1b, 1c, 1d, 1e, 1p, 1s, giving the push-pull-butadiene derivatives 35a-f, 36a-f, 37a-j, 38a, b, 39a, b, 40a, b. Crystal structure analyses of the butadiene derivatives 37a, 39a, b, 40a, b and 42 were performed, showing that in 37a, 39b, 40a, b by far the shortest bond distance is between C-2 and C-3 of the butadiene system. In 39a the bonds between C1-C2, C2-C3 and C3-C4 are nearly of equal length, whereas in the 1,3-diene unit of 42 the shortest bonds are between C1-C2 and C3-C4.

N,N'-Persubstituted selenoacrylamides (4), easily available by reaction of 1-chlorovinamidinium salts (2) with sodium selenide, were transformed by means of acceptor-substituted halomethyl compounds (9-14) into new 2-aminoselenophene derivatives (15-20).Their UV/ vis data are presented, and the positive solvatochromism of 2-R 2 N-5-acceptor-substituted selenophenes is reported.

Treatment of semicyclic 3-trifloxypropene iminium triflates 4a -c,e,f, in which the iminium function is part of a six-membered ring, with a polymer-supported tertiary amine leads to 3- [(trifluoromethyl)sulfonyl]-1,4,5,6-tetrahydropyridines 7.Related five- and seven-membered cyclic iminium salts do not react to give the corresponding enaminosulfones.

For stereochemical investigation of their dehydrogenation, the enantiomers of the aminoalcohols 1, 2, and 3 were prepared from optically active sources, while the enantiomers of the diamines 8 and 9 were available by resolution of the racemates.T he pure antipodes of 1, 2, and 3 reacted with mercury(II)-EDTA by a twofold dehydrogenation via intermediate participation of the neighbouring alcoholic group to the optically active lactams 5, 6, and 7 under complete retention of configuration.In the same manner the diamines 8 and 9 generated by four electron withdrawal the cycloamidines 10 and 11.

2,2,N-Trimethyl-N-phenyl-2H-azirin-3-amine (1a) was prepared by successive treatment of 2,N-dimethyl-N-phenylpropanamide (18) with phosgene, triethylamine, and sodium azide. Reaction of 1a in THF solution with boron trifluoride gave 2-amino-1,3,3-trimethyl-3H-indolium tetrafluoroborate (19) in high yield.T he latter reacted with acetic anhydride in pyridine to give a mixture of N-(2,3-dihydro-1,3,3-trimethylindol-2-yliden)acetamide (22) and 2,3-dihydro- 1,3,3-trimethylindol-2-one (21).On hydrolysis with aqueous HCl, 22 was converted to 21.T he molecular structures of 19 and 22 were established by X-ray crystal structure determination.

3-Substituted 5-[(Z)-heteroarylmethylidene]imidazolidine-2,4-dione and 5-[(Z)-heteroarylmethylidene]- 2-thiooxoimidazolidin-4-one derivatives were prepared stereoselectively by coupling of 5-(dimethylamino)methylidene substituted hydantoin and thiohydantoin derivatives with carbocyclic and heterocyclic C-nucleophiles.Configuration around the exocyclic C=C double bond was determined by NMR, using NOESY and 2D HMBC techniques.

Ethenetetracarbonitrile (2, in benzene solution) and 1,3-dioxoindan-2-ylidene propanedinitrile (4, in ethanol or acetonitrile solution) act on N-aryl-2,3-dihydro-1H-benz[d,e]isoquinolines 6a-d and N-aryl-6,7-dihydro-5H-dibenz[c,e]azepines 11a-d via hydride abstraction followed by addition of cyanide to the iminium carbon atom forming the corresponding 1- and 5-carbonitriles 9a-d and 13a-d, respectively, in moderate to medium yields.Additionally , the known 1,3-dihydroxy-2H-inden-2-ylidenepropanedinitrile 15 and a novel dispirocyclopropane (17) are formed from 4 in the reaction with 6 in acetonitrile and ethanol, respectively. The structures of 17 and 6-(4-methylphenyl)-6,7-dihydro-5H-dibenz[c,e]azepine-5-carbonitrile have been unambiguously confirmed by single-crystal X-ray crystallography.

The easily available pyrido[1,2-a]pyrazines of type 1 are versatile building blocks for ring transformation reactions.W ith heterocyclic quinones such as quinoline-2,5,8-triones 4a-c, a highly regioselective [4+2]-cycloaddition reaction takes place in the first step, followed by a ring transformation cascade.T he 1,6-diazaanthracene-2,9,10-triones 5a-e, which possess an additional bipyridine substructure, could be isolated as main products.In order to modify the starting products of type 1, a metal-catalyzed cross-coupling reaction with acetylenic benzoic esters 9a,b has been performed.T he modified pyridopyrazines 10a,b which were obtained in good yields could be transformed by analogy to 1a,b into ring-fused heterocyclic quinones 12a,b.