New theoretically predicted RDX‐ and β‐HMX‐based high‐energy‐density molecules

Theoretically new high‐energy‐density materials (HEDM) in which the hydrogens on RDX and β‐HMX (hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine and octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine, respectively) were sequentially replaced by (N NO₂)x functional groups were designed and evaluated using density functional theory calculations in combination with the Kamlet–Jacobs equations and an atoms‐in‐molecules (AIM) analysis. Improved detonation properties and reduced sensitivity compared to RDX and β‐HMX were predicted. Interestingly, the RDX and β‐HMX derivatives having one attached N NO₂ group [RDX‐(NNO₂)1 and HMX‐(NNO₂)1] showed excellent detonation properties (detonation velocities: 9.529 and 9.575 km·s⁻¹, and detonation pressures: 40.818 and 41.570 GPa, respectively), which were superior to the parent compounds. Sensitivity estimations obtained by calculating impact sensitivities and HOMO‐LUMO gaps indicated that RDX‐(NNO₂)1 and HMX‐(NNO₂)1 were less stable than RDX and HMX but more stable than any of the other derivatives. This method of sequential NNO₂ group attachment on conventional HEDMs offers a firm basis for further studies on the design of new explosives. Furthermore, the newly found structures may be promising candidates for better HEDMs.     

Azetidine,pyrrolidine and hexamethyleneimine at 170 K

The crystal structures of the cyclic amines azetidine (C₃H₇N), pyrrolidine (C₄H₉N) and hexamethyleneimine (homopiperidine, C₆H₁₃N), of the series (CH₂)_nNH, with n = 3, 4 and 6, respectively, have been determined at 170 K, following in situ crystallization from the melt. These structures provide crystallographic data to complete the homologous series of cyclic amines (CH₂)_nNH, for n = 2–6. Azetidine and pyrrolidine contain chains propagating along 2₁ screw axes, in which the molecules are linked by co-operative N—H...N hydrogen bonds. Azetidine has two molecules in its asymmetric unit, while pyrrolidine has only one. Hexamethyleneimine contains tetrameric hydrogen-bonded rings formed about crystallographic inversion centres, with two molecules in its asymmetric unit. The observation of crystallographically distinct molecules in the hydrogen-bonded chains of azetidine and cyclic hydrogen-bonded motifs in hexamethyleneimine is consistent with expectations derived from comparison with monoalcohols forming chains or rings by co-operative O—H...O hydrogen bonds. The next member of the cyclic amine series, heptamethyleneimine, forms a cubic plastic phase on cooling from the melt.     

Synthesis and properties of oligo(biradicals) composed of 1,3‐diphosphacyclobutane‐2,4‐diyl units and benzyl‐type linkers

We have succeeded in catenating two sterically encumbered 1,3‐di‐t‐butyl‐2,4‐bis(2,4,6‐tri‐t‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl units with a spacer 1,2‐(CH₂)₂C₆H₄ to obtain bis(biradicals) as considerably stable compounds. We have discussed physicochemical properties of the dimer, together with DFT calculations of model compounds. Spectroscopic data, redox properties, and X‐ray structures of the oligo(biradicals) derivatives including other spacers like 1,3‐(CH₂)₂C₆H₄, 1,4‐(CH₂)₂C₆H₄, and 1,3,5‐(CH₂)₃C₆H₃, reveal that the P‐heterocyclic biradical moieties interact through nonconjugative pathways. These properties of oligo(biradicals) will facilitate to design novel molecular systems for electronics. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:404–411, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20625     

Synthesis,Characterization, and Crystal Structure of 1,3‐Dipentafluorophenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine

1,3‐Dipentafluorophenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine ( 1 ) was synthesized by the reaction of [(C₆F₅)NPCl₃]₂ with trimethylsilyl azide in CH₂Cl₂ and characterized by multinuclear NMR and vibrational spectroscopy. The molecular structure of the compound was determined by single‐crystal X‐ray structure analysis. [(C₆F₅)NP(N₃)₃]₂ crystallizes in the monoclinic space group P2₁/n with a = 9.6414(2), b = 7.4170(1) and c = 15.9447(4) Å, β = 94.4374(9)°, with 2 formula units per unit cell. The bond situation in [(C₆F₅)NP(N₃)₃]₂ has been studied on the basis of NBO analysis. The antisymmetric stretching vibration of the azide groups is discussed. The structural diversity of 1 and 1,3‐diphenyl‐2,2,2,4,4,4‐hexazido‐1,3‐diaza‐2,4‐diphosphetidine in solution and in the solid state depending on the aryl substituent at the nitrogen atom is discussed.     

The dimer,trimer and 1,2,4‐tri­thiol­ane of adamantane­thione

The mol­ecules of di­spiro­[1,3‐dithietane‐2,2′:4,2′′‐diadamantane], C₂₀H₂₈S₂, have crystallographic C_i symmetry, as well as local D_2h symmetry, and a planar 1,3‐dithietane ring. The mol­ecules of tri­spiro­[1,3,5‐tri­thia­ne‐2,2′:4,2′′:6,2′′′‐triadamantane], C₃₀H₄₂S₃, have approximate C₂ symmetry and the 1,3,5‐tri­thia­ne ring has a twist–boat conformation. The C—S—C bond angles within the ring are about 8° larger than observed in most related 1,3,5‐tri­thia­ne structures. In di­spiro­[1,2,4‐tri­thiol­ane‐3,2′:5,2′′‐diadamantane], C₂₀H₂₈S₃, the mol­ecules have local C₂ symmetry and the 1,2,4‐tri­thiol­ane ring has a half‐chair conformation.     

1,3‐Bis(ethylamino)‐2‐nitrobenzene, 1,3‐bis(n‐octylamino)‐2‐nitrobenzene and 4‐ethylamino‐2‐methyl‐1H‐benzimidazole

1,3‐Bis(ethylamino)‐2‐nitrobenzene, C₁₀H₁₅N₃O₂, (I), and 1,3‐bis(n‐octylamino)‐2‐nitrobenzene, C₂₂H₃₉N₃O₂, (II), are the first structurally characterized 1,3‐bis(n‐alkylamino)‐2‐nitrobenzenes. Both molecules are bisected though the nitro N atom and the 2‐C and 5‐C atoms of the ring by twofold rotation axes. Both display intramolecular N—H...O hydrogen bonds between the amine and nitro groups, but no intermolecular hydrogen bonding. The nearly planar molecules pack into flat layers ca 3.4 Å apart that interact by hydrophobic interactions involving the n‐alkyl groups rather than by π–π interactions between the rings. The intra‐ and intermolecular interactions in these molecules are of interest in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethylacetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4‐ethylamino‐2‐methyl‐1H‐benzimidazole, C₁₀H₁₃N₃, (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent molecules with no imposed internal symmetry. The molecules are linked into chains via N—H...N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4‐amino and 2‐alkyl substituents.     

Stereochemie vonGrignard-Reaktione mit 2-(N-Methylanikino)-cyclopentanonen

TheGrignard reactions of the 2-anilinocyclopentanones (1 a and1 b) with CH₃MgI and C₆H₅CCMgBr, giving the 2-anilinocyclopentanols2 a, 2 b, and2 c, and the synthesis oftrans-1-methyl-2-(4-chloro-N-methylanilino)-cyclopentanol (4), which was used as a reference compound of known stereochemistry, are described. IR spectroscopic investigations of2 a, 2 b, and2 c as compared with4 lead to the conclusion that2 a, 2 b, and2 c have the structures ofcis-2-(N-methylanilino)-cyclopentanols.     

Selective Metal‐free HB(C6F5)2 Catalyzed Allene Cyclotrimerization: Formation of 1,3,5‐Trimethylenecyclohexane and Its Tris‐hydroboration Product

Allene is cyclotrimerized under metal‐free conditions with the borane HB(C₆F₅)₂ catalyst to selectively give 1,3,5‐trimethylenecyclohexane ( 3 a ). Three‐fold hydroboration of the 1,3,5‐cyclotrimer with Piers’ borane gives the all‐cis 1,3,5‐CH₂B(C₆F₅)₂ substituted cyclohexane product 14 .     

Tri­azido­cobalt(III) complexes with tridentate amine ligands

The title compounds, [N‐(2‐amino­ethyl)‐1,3‐propane­di­amine‐κ³N]­tri­azido­cobalt(III), [Co(N₃)₃(C₅H₁₅N₃)], [N‐(2‐amino­ethyl)‐N‐methyl‐1,3‐propane­di­amine‐κ³N]­tri­azido­cobalt(III), [Co(N₃)₃(C₆H₁₇N₃)], [N‐(2‐amino­propyl)‐1,3‐pro­pane­di­am­ine‐κ³N]­tri­azido­cobalt(III), [Co(N₃)₃(C₆H₁₇N₃)], and [N‐(2‐amino­propyl)‐N‐methyl‐1,3‐pro­pane­di­am­ine‐κ³N]triazidocobalt(III), [Co(N₃)₃­(C₇­H₁₉­N₃)], each consist of a Co^III atom, three azide ligands in a meridional configuration and a tridentate amine ligand, namely aepn [N‐(2‐amino­ethyl)‐1,3‐propane­di­amine] or dpt [N‐(3‐amino­propyl)‐1,3‐pro­pane­di­amine], or their N‐methyl­­ated analogs.     

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, 2,6‐bis(ethylamino)‐3‐nitrobenzonitrile and bis(4‐ethylamino‐3‐nitrophenyl) sulfone

N,N′‐Diethyl‐4‐nitrobenzene‐1,3‐diamine, C₁₀H₁₅N₃O₂, (I), crystallizes with two independent molecules in the asymmetric unit, both of which are nearly planar. The molecules differ in the conformation of the ethylamine group trans to the nitro group. Both molecules contain intramolecular N—H...O hydrogen bonds between the adjacent amine and nitro groups and are linked into one‐dimensional chains by intermolecular N—H...O hydrogen bonds. The chains are organized in layers parallel to (101) with separations of ca 3.4 Å between adjacent sheets. The packing is quite different from what was observed in isomeric 1,3‐bis(ethylamino)‐2‐nitrobenzene. 2,6‐Bis(ethylamino)‐3‐nitrobenzonitrile, C₁₁H₁₄N₄O₂, (II), differs from (I) only in the presence of the nitrile functionality between the two ethylamine groups. Compound (II) crystallizes with one unique molecule in the asymmetric unit. In contrast with (I), one of the ethylamine groups, which is disordered over two sites with occupancies of 0.75 and 0.25, is positioned so that the methyl group is directed out of the plane of the ring by approximately 85°. This ethylamine group forms an intramolecular N—H...O hydrogen bond with the adjacent nitro group. The packing in (II) is very different from that in (I). Molecules of (II) are linked by both intermolecular amine–nitro N—H...O and amine–nitrile N—H...N hydrogen bonds into a two‐dimensional network in the (10) plane. Alternating molecules are approximately orthogonal to one another, indicating that π–π interactions are not a significant factor in the packing. Bis(4‐ethylamino‐3‐nitrophenyl) sulfone, C₁₆H₁₈N₄O₆S, (III), contains the same ortho nitro/ethylamine pairing as in (I), with the position para to the nitro group occupied by the sulfone instead of a second ethylamine group. Each 4‐ethylamino‐3‐nitrobenzene moiety is nearly planar and contains the typical intramolecular N—H...O hydrogen bond. Due to the tetrahedral geometry about the S atom, the molecules of (III) adopt an overall V shape. There are no intermolecular amine–nitro hydrogen bonds. Rather, each amine H atom has a long (H...O ca 2.8 Å) interaction with one of the sulfone O atoms. Molecules of (III) are thus linked by amine–sulfone N—H...O hydrogen bonds into zigzag double chains running along [001]. Taken together, these structures demonstrate that small changes in the functionalization of ethylamine–nitroarenes cause significant differences in the intermolecular interactions and packing.     

A structural study of (1RS,2SR,3RS,4SR,5RS)‐2,4‐dibenzoyl‐1,3,5‐triphenylcyclohexan‐1‐ol chloroform hemisolvate and (1RS,2SR,3RS,4SR,5RS)‐2,4‐dibenzoyl‐1‐phenyl‐3,5‐bis(2‐methoxyphenyl)cyclohexan‐1‐ol

(1RS,2SR,3RS,4SR,5RS)‐2,4‐Dibenzoyl‐1,3,5‐triphenylcyclohexan‐1‐ol or (4‐hydroxy‐2,4,6‐triphenylcyclohexane‐1,3‐diyl)bis(phenylmethanone), C₃₈H₃₂O₃, (1), is formed as a by‐product in the NaOH‐catalyzed synthesis of 1,3,5‐triphenylpentane‐1,5‐dione from acetophenone and benzaldehyde. Single crystals of the chloroform hemisolvate, C₃₈H₃₂O₃·0.5CHCl₃, were grown from chloroform. The structure has triclinic (P) symmetry. One diastereomer [as a pair of (1RS,2SR,3RS,4SR,5RS)‐enantiomers] of (1) has been found in the crystal structure and confirmed by NMR studies. The dichoromethane hemisolvate has been reported previously [Zhang et al. (2007). Acta Cryst. E 63 , o4652]. (1RS,2SR,3RS,4SR,5RS)‐2,4‐Dibenzoyl‐3,5‐bis(2‐methoxyphenyl)‐1‐phenylcyclohexan‐1‐ol or [4‐hydroxy‐2,6‐bis(2‐methoxyphenyl)‐4‐phenylcyclohexane‐1,3‐diyl]bis(phenylmethanone), C₄₀H₃₆O₅, (2), is also formed as a by‐product, under the same conditions, from acetophenone and 2‐methoxybenzaldehyde. Crystals of (2) have been grown from chloroform. The structure has orthorhombic (Pca2₁) symmetry. A diastereomer of (2) possesses the same configuration as (1). In both structures, the cyclohexane ring adopts a chair conformation with all bulky groups (benzoyl, phenyl and 2‐methoxyphenyl) in equatorial positions. The molecules of (1) and (2) both display one intramolecular O—H...O hydrogen bond.     

Cyclothiomethylation of aryl hydrazines with formaldehyde and hydrogen sulfide

Cyclothiomethylation of phenyl hydrazine with CH₂O and H₂S in a ratio of 1: 3: 2 in an acidic medium (HCl) afforded previously unknown 3-phenyl-1,3,4-thiadiazolidine (35% yield) and N-phenyl(perhydro-1,3,5-dithiazin-5-yl)amine (35% yield). The analogous reaction in an alkaline medium (BuONa) produced N-phenyl(perhydro-1,3-thiazetidin-3-yl)amine (22% yield). The reaction of 1,2-diphenyl hydrazine with CH₂O and H₂S in an alkaline medium gave 1,2,4,5-tetraphenylhexahydro-1,2,4,5-tetrazine and previously unknown 3,4-diphenyl-1,3,4-thiadiazolidine and 5,6-diphenyltetrahydro-1,3,5,6-dithiadiazepine in 39 and 22% yields, respectively. Cyclothiomethylation of benzyl hydrazine afforded previously unknown bis[(6-benzyl-4,2,6-thiadiazolidin-2-yl)methyl] sulfide (60% yield) and N-benzyl(perhydro-1,3,5-dithiazin-5-yl)amine (19% yield). The reaction of tosyl hydrazine produced 3-[(p-tolyl)sulfonyl]-1,3,4-thiadiazolidine, N-(perhydro-1,3,5-dithiazin-5-yl)-p-tolylsulfonamide, and 3,7-bis(p-tolylsulfonylamino)-1,5-dithia-3,7-diazacyclooctane in 21, 38, and 41% yields, respectively. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1758–1767, October, 2006.     

4,6‐Dinitro‐N,N′‐di‐n‐octylbenzene‐1,3‐diamine, 4,6‐dinitro‐N,N′‐di‐n‐undecylbenzene‐1,3‐diamine and N,N′‐bis(2,4‐dinitrophenyl)octane‐1,8‐diamine

4,6‐Dinitro‐N,N′‐di‐n‐octylbenzene‐1,3‐diamine, C₂₂H₃₈N₄O₄, (I), 4,6‐dinitro‐N,N′‐di‐n‐undecylbenzene‐1,3‐diamine, C₂₈H₅₀N₄O₄, (II), and N,N′‐bis(2,4‐dinitrophenyl)octane‐1,8‐diamine, C₂₀H₂₄N₆O₈, (III), are the first synthetic meta‐dinitroarenes functionalized with long‐chain aliphatic amine groups to be structurally characterized. The intra‐ and intermolecular interactions in these model compounds provide information that can be used to help understand the physical properties of corresponding polymers with similar functionalities. Compounds (I) and (II) possess near‐mirror symmetry, with the octyl and undecyl chains adopting fully extended anti conformations in the same direction with respect to the ring. Compound (III) rests on a center of inversion that occupies the mid‐point of the central C—C bond of the octyl chain. The middle six C atoms of the chain form an anti arrangement, while the remaining two C atoms take hard turns almost perpendicular to the rest of the chain. All three molecules display intramolecular N—H...O hydrogen bonds between the amine and nitro groups, with the same NH group forming a bifurcated intermolecular hydrogen bond to the nitro O atom of an adjacent molecule. In each case, these interactions link the molecules into one‐dimensional molecular chains. In (I) and (II), these chains pack so that the pendant alkyl groups are interleaved parallel to one another, maximizing nonbonded C—H contacts. In (III), the alkyl groups are more isolated within the molecular chains and the primary nonbonded contacts between the chains appear to involve the nitro groups not involved in the hydrogen bonding.     

EQUILIBRIA AND REACTION RATES OF PHOSPHORUS SUBSTITUTION REACTIONS IN 2-R-1,3,2-DISUBSTITUTED PHOSPHORINANES

Abstract

Equilibrium constants and reaction times were observed for six equilibria involving methanol, ethanol, dimethylamine, diethylamine and pyrrolidine with 2-R-1,3,2-dioxaphosphorinanes wherein R = MeO (1), EtO (2), Me₂N (3), Et₂N (4) and (CH₂)₄N (5), or 2-R-1,3-dimethyl-1,3,2-diazaphosphorinanes wherein R equalled the same five groups (6–10, respectively). Reaction times of amine substitutions were shorter for diaza compounds and for those reactions which contained pyrrolidine. Equilibrium constants were dependent not only upon the nucleophilicities of the exchanging groups, but also upon the steric interactions of the 2-substituents with the groups in the 1 and 3 positions. Thus, the values of K's for the equilibria 5 + Me₂NH → 3 + (CH₂)₄NH, and 10 + Me₂NH → 8 + (CH₂)₄NH were experimentally identical, whereas K for 9 + Me₂NH → 8 + Et₂NH was ca. eight times that for 4 + Me₂NH → 3 + Et₂NH. The reactions were acid catalyzed, and, for amine substitutions with 8–10, exchange could be rapid on the NMR time scale. Equilibrium positions of amine-containing reactions were [H⁺] dependent, where coordination of the less basic amine to phosphorus became increasingly favored by the addition of acid. These observations raise questions about a recent mechanistic proposal for catalyzed substitution reactions. Similar substitution reactions, such as Me₂NH with the isomeric 4-methyl analogues of 3, provide a procedure for the determination of cis-trans isomer equilibrium distributions.     

Synthesis of amino-substituted 1,3-bis(tert-butyl-NNO-azoxy)benzenes 2.* 2-amino and 2,4-diamino derivatives

Oxidation of one of the amino groups of 2-bromo-4,6-dichloro-1,3-phenylenediamine to the nitroso group followed by its conversion into thetert-butyl-NNO-azoxy group afforded a derivative ofm-(tert-butyl-NNO-azoxy)aniline,viz., 2-bromo-3-(tert-butyl-NNO-azoxyl)-4,6-dichloroaniline. Analogously, the second amino group was converted into thetert-butyl-NNO-azoxy group to form a derivative of 1,3-bis(tert-butyl-NNO-azoxy)benzene,viz., 3-bromo-2,4-bis(tert-butyl-NNO-azoxyl)-1,5-dichlorobenzene The reaction of the latter with ammonia yielded 2-amino- and 2,4-diamino-substituted 1,3-bis-(tert-butyl-NNO-azoxyl)benzenes. For Part 1, see Ref. 1. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2126–2130, November, 1999.     

Synthesis of 5-amino-6-nitro-1,2,3,4-tetrazine 1,3-dioxide

5-Amino-(tert-butyl-NNO-azoxy)-1,2,3,4-tetrazine 1,3-dioxide reacts with nitronium tetra-fluoroborate to give 5-amino-6-nitro-1,2,3,4-tetrazine 1,3-dioxide. This compound is of interest as a new energetic material. A plausible reaction mechanism involves electrophilic substitution of the tert-butyl-NNO-azoxy group by the nitro group.

     

Bis[μ‐2‐({2‐[2‐(2‐chlorophenoxy)‐1‐oxidoethylidene]hydrazinylidene}methyl)phenolato]bis[pyridinecopper(II)] methanol disolvate

In the title compound, [Cu₂(C₁₅H₁₁ClN₂O₃)₂(C₅H₅N)₂]·2CH₃OH, the coordination geometry of the metal centre can be described as square pyramidal. Pairs of pentacoordinated metal centres are bridged by symmetry‐related phenolate O atoms about the inversion centre at (, 0, ), resulting in a binuclear metal cluster via edge‐sharing.     

Tridentate Lewis Acids Based on 1,3,5‐Trisilacyclohexane Backbones and an Example of Their Host–Guest Chemistry

Directed tridentate Lewis acids based on the 1,3,5‐trisilacyclohexane skeleton with three ethynyl groups [CH₂Si(Me)(C₂H)]₃ were synthesised and functionalised by hydroboration with HB(C₆F₅)₂, yielding the ethenylborane {CH₂Si(Me)[C₂H₂B(C₆F₅)₂]}₃, and by metalation with gallium and indium organyls affording {CH₂Si(Me)[C₂M(R)₂]}₃ (M=Ga, In, R=Me, Et). In the synthesis of the backbone the influence of substituents (MeO, EtO and iPrO groups at Si) on the orientation of the methyl group was studied with the aim to increase the abundance of the all‐cis isomer. New compounds were identified by elemental analyses, multi‐nuclear NMR spectroscopy and in some cases by IR spectroscopy. Crystal structures were obtained for cis‐trans‐[CH₂Si(Me)(Cl)]₃, all‐cis‐[CH₂Si(Me)(H)]₃, all‐cis‐[CH₂Si(Me)(C₂H)]₃, cis‐trans‐[CH₂Si(Me)(C₂H)]₃ and all‐cis‐[CH₂Si(Me)(C₂SiMe₃)]₃. A gas‐phase electron diffraction experiment for all‐cis‐[CH₂Si(Me)(C₂H)]₃ provides information on the relative stabilities of the all‐equatorial and all‐axial form; the first is preferred in both solid and gas phase. The gallium‐based Lewis acid {CH₂Si(Me)[C₂Ga(Et)₂]}₃ was reacted with a tridentate Lewis base (1,3,5‐trimethyl‐1,3,5‐triazacyclohexane) in an NMR titration experiment. The generated host–guest complexes involved in the equilibria during this reaction were identified by DOSY NMR spectroscopy by comparing measured diffusion coefficients with those of the suitable reference compounds of same size and shape.     

New dithiazinanes and bis‐dithiazinanes‐bearing pendant ethylamines: Structure and reactivity

The structure and reactivity of a series of new ethylaminedithiazinanes and bis‐diethylaminedithiazinanes synthesized from formaldehyde, NaSH, and N,N‐dimethyl‐ethylene‐diamine ( 1 ), N‐methyl‐ethylene‐diamine ( 2 ), and N‐ethyl‐ethylene‐diamine ( 3 ) are reported. Compound 1 afforded 2‐([1,3,5]‐dithiazinan‐5‐yl)‐ethylene‐N,N‐dimethyl‐amine ( 4 ). The reaction of 4 with dry CH₂Cl₂ gave N‐{2‐([1,3,5]dithiazinan‐5‐yl)‐ethylene}‐N‐chloromethyl‐N,N‐dimethyl‐ammonium chloride ( 5 ) in high yield, whereas in wet CH₂Cl₂ and DMSO provided a mixture of 5 with N‐{2‐([1,3,5]‐dithiazinan‐5‐yl)‐ethylene}‐N,N‐dimethyl‐ammonium hydrochloride ( 6 ).bis‐{2‐([1,3,5]‐Dithiazinan‐5‐yl)‐ethylene‐N‐alkyl‐amino}‐methylene‐disulfides ( 7 ) and ( 8 ) formed by two dithiazinanes linked through the chain  (CH₂)₂ NRCH₂ S S CH₂ NR (CH₂)₂‐ ( 7 R = methyl, 8 R = ethyl) reacted with CH₂Cl₂ giving after neutralization of the hydrolysis products the ethylaminedithiazinanes with different pendant N‐groups [ (CH₂)₂NMeH₂⁺( 9 );  (CH₂)₂NEtH₂⁺ ( 10 );  (CH₂)₂NMeH ( 11 );  (CH₂)₂NEtH ( 12 );  (CH₂)₂NMeHBH₃ ( 13 )  (CH₂)₂NEtHBH₃ ( 14 ).  (CH₂)₂NMe₂BH₃ ( 15 ), and  (CH₂)₂NEtMeBH₃.( 16 )]. The x‐ray diffraction analyses of compounds 5 , 6 , 9 , and 10 are reported. Variable temperature NMR experiments afforded the Δ G^≠ of the ring interconversion of the six‐membered heterocycles 6 , 9 , and 10 . © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:59–71, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20657     

Structures and energies of seleno derivatives of biuret.Ab Initio comparative studies of diselenobiuret, selenobiuret, and selenothiobiuret

Ab initio studies (LCAO-MO method) on conformers of three seleno derivatives of the biuret molecules diselenobiuret [I], selenobiuret [II], and selenothiobiuret [III] were carried out at the Hartree-Fock (HF) and MP2 levels. The molecular geometries of these species were fully optimized at the HF level and characterized by analysis of the harmonic vibrational frequencies using a split-valence triple-zeta basis set augmented by a set ofd polarization functions on heavy atoms andp polarization functions on hydrogen atoms [TZP(d, p)]. The total energies of the HF-optimized structures were calculated at the MP2 (frozen core) level using a larger TZP (2df, 2pd) basis set. The potential energy searches revealed a total of 11 minimum-energy conformers (assigned astrans-trans, trans-cis, cis-trans, andcis-cis) and seven transition-state species for the title molecules. The two predicted conformers for diselenobiuret (Ia=trans-trans andIc=cis-cis) are characterized byC ₂ and the third byC _s symmetry. For selenothiobiuret two forms (IIIa=trans-trans andIIId=cis-cis) possessC ₁ and two (IIIb=trans-cis andIIIc=cis-trans) possessC _s symmetries, respectively. For selenobiuret, four formsIIa=trans-trans (C₁),IIb=trans-cis (C _s),IIc=cis-trans (C ₁), andIId=cis-cis (C₁), were obtained as a result of gradient optimization. Comparison of the relative energies for the considered species indicated that thecis-trans forms are the most stable conformations for all three systems at both the HF and MP2 levels of theory.