Studies of Some Strained Organic Molecules

<p>The characterisation of rare examples of C1-substituted cyclopropanaphthalenes has been achieved with silanes (104) and (112) by employing the C1 anion (106). With toluene, N,N-dimethylacetamide, and cyclopropanaphthalene (58) this same anion gives the novel 6-methyl-7H-dibenzo[b,g]fluorene (179), a formal dimer of cycloproparene (58). Hydrocarbon (179) is the sole dibenzo[b,g]hydrocarbon characterised and this has required extensive spectroscopic study with confirmation from X-ray analysis. A possible new route to alkylidenecyclopropanaphthalenes (114) employing lithiate (170) and either cycloproparene (58) or its disilyl analogue (105) was found to offer no advantage over known procedures. Application of the protocols embodied in this procedure to brominated synthons (114o) and (114p) has afforded novel pi-extended methylidene compounds (197a) and (199) in low yield. Cyclopentadienylidene (197a) has also been prepared in better yield from benzophenone-containing methylidenecycloproparene (200). Initial attempts to obtain (200) from anion (193) and N,N-dimethylbenzamide were unsuccessful and gave instead the new phenol (114q). The first acylcycloproparenes (189) and (202) have been obtained in modest yield from anion (103) and N,N-dimethyl-acetamide, and -benzamide. With N,N-dimethyl-carbamoyl chloride anion (103) gives the bis-amide (205). With hydrochloric acid these acylcycloproparenes give rise to 2,3-disubstituted naphthalenes rather than 2-substituted naphthalenes that typically arise from protonation at the aromatic ring. Thermolysis leads to ring expansion and naphthofuran formation. Enolate formation from the 1-acyl-cyclopropanaphthalenes (189) and (202) and anion capture at oxygen affords the first cyclopropanaphthalenylidene enol ethers (219) and (220). 1H-Cyclopropa[b]naphthalene-3,6-dione (154) adds buta-1,3-diene across the enedione Pi-bond to give the tetrahydrocyclopropanthraquinone (160). Enolisation of (160) provides phenolate (234) that can be diverted to ether (229) or oxidised to the dihydroanthraquinone (230). Dehydrogenation of (229) is readily achieved and gives the first anthraquinone of the cycloproparene series 1H-cyclopropa[b]anthracene-3,8-dione (162); quinone (162) is only the second cyclopropaquinone to have been characterised. Alternative routes to quinone (162) and its 3,8-dimethoxy analogue (163) have been examined with a view to providing the first alkylidenecyclopropanthracenes. The first examples of cross-conjugated dithiole-containing cycloproparenes, (169) and (267), have been prepared from cyclopropanthraquinone (162) but they are unstable solids. The pi-extended dithiole-containing methylidene compound (273) has been prepared in good yield from Wittig-Horner olefination of the benzoylmethylidene compound (200). Evidence was obtained to support the formation of a charge-transfer complex from it. Ketones already carrying a conjugated dithiole moiety participate in the Peterson olefination with the alpha-silyl anion (106) and give the new pi-extended methylidenecyclopropanaphthalenes (274) and (277) of limited stability.</p>

Studies of Some Strained Organic Molecules

<p>The characterisation of rare examples of C1-substituted cyclopropanaphthalenes has been achieved with silanes (104) and (112) by employing the C1 anion (106). With toluene, N,N-dimethylacetamide, and cyclopropanaphthalene (58) this same anion gives the novel 6-methyl-7H-dibenzo[b,g]fluorene (179), a formal dimer of cycloproparene (58). Hydrocarbon (179) is the sole dibenzo[b,g]hydrocarbon characterised and this has required extensive spectroscopic study with confirmation from X-ray analysis. A possible new route to alkylidenecyclopropanaphthalenes (114) employing lithiate (170) and either cycloproparene (58) or its disilyl analogue (105) was found to offer no advantage over known procedures. Application of the protocols embodied in this procedure to brominated synthons (114o) and (114p) has afforded novel pi-extended methylidene compounds (197a) and (199) in low yield. Cyclopentadienylidene (197a) has also been prepared in better yield from benzophenone-containing methylidenecycloproparene (200). Initial attempts to obtain (200) from anion (193) and N,N-dimethylbenzamide were unsuccessful and gave instead the new phenol (114q). The first acylcycloproparenes (189) and (202) have been obtained in modest yield from anion (103) and N,N-dimethyl-acetamide, and -benzamide. With N,N-dimethyl-carbamoyl chloride anion (103) gives the bis-amide (205). With hydrochloric acid these acylcycloproparenes give rise to 2,3-disubstituted naphthalenes rather than 2-substituted naphthalenes that typically arise from protonation at the aromatic ring. Thermolysis leads to ring expansion and naphthofuran formation. Enolate formation from the 1-acyl-cyclopropanaphthalenes (189) and (202) and anion capture at oxygen affords the first cyclopropanaphthalenylidene enol ethers (219) and (220). 1H-Cyclopropa[b]naphthalene-3,6-dione (154) adds buta-1,3-diene across the enedione Pi-bond to give the tetrahydrocyclopropanthraquinone (160). Enolisation of (160) provides phenolate (234) that can be diverted to ether (229) or oxidised to the dihydroanthraquinone (230). Dehydrogenation of (229) is readily achieved and gives the first anthraquinone of the cycloproparene series 1H-cyclopropa[b]anthracene-3,8-dione (162); quinone (162) is only the second cyclopropaquinone to have been characterised. Alternative routes to quinone (162) and its 3,8-dimethoxy analogue (163) have been examined with a view to providing the first alkylidenecyclopropanthracenes. The first examples of cross-conjugated dithiole-containing cycloproparenes, (169) and (267), have been prepared from cyclopropanthraquinone (162) but they are unstable solids. The pi-extended dithiole-containing methylidene compound (273) has been prepared in good yield from Wittig-Horner olefination of the benzoylmethylidene compound (200). Evidence was obtained to support the formation of a charge-transfer complex from it. Ketones already carrying a conjugated dithiole moiety participate in the Peterson olefination with the alpha-silyl anion (106) and give the new pi-extended methylidenecyclopropanaphthalenes (274) and (277) of limited stability.</p>

Crystal structures of 6-nitroquinazolin-4(3H)-one, 6-aminoquinazolin-4(3H)-one and 4-aminoquinazoline hemihydrochloride dihydrate

The title compounds, 6-nitroquinazolin-4(3H)-one (C8H5N3O3; I), 6-aminoquinazolin-4(3H)-one (C8H7N3O; II) and 4-aminoquinazolin-1-ium chloride–4-aminoquinazoline–water (1/1/2), (C8H8N3 +·Cl−·C8H7N3·2H2O; III) were synthesized and their structures were determined by single-crystal X-ray analysis. In the crystals of I and II, the quinazoline molecules form hydrogen-bonded dimers via N—H...O interactions. The dimers are connected by weak intermolecular C—H...N and C—H...O hydrogen bonds, forming a layered structure in the case of I. In the crystal of II, N—H...N and C—H...O interactions link the dimers into a three-dimensional network structure. The asymmetric unit of III consists of two quinazoline molecules, one of which is protonated, a chloride ion, and two water molecules. The chloride anion and the water molecules form hydrogen-bonded chains consisting of fused five-membered rings. The protonated and unprotonated quinazolin molecules are linked to the chloride ions and water molecules of the chain by their amino groups.

Bonding features in Appel's salt from the orbital-free quantum crystallographic perspective

Bonding properties in the crystal of 4,5-dichloro-l,2,3-dithiazolium chloride (Appel's salt) were studied using a combination of single-crystal high-resolution X-ray diffraction data and the orbital-free quantum crystallography approach. A QTAIM-based topological model shows the proximity of S—C and S—N bonds to the sesquialteral type and establishes the low S—S bond order in the l,2,3-dithiazolium heterocycle. It is found that the electrostatic potential carries the traces of a common positive area on the junction of interatomic zero-flux surfaces of S1 and S2 atomic basins; meanwhile the exchange energy density per particle shows perfectly here two separate minima through which the two bond paths run. Thus, the pair intermolecular interactions Cl−...S1 and Cl−...S2 formed by the common chloride anion placed near the center of the S—S bond are categorized as chalcogen bonds.

Crystal structure of donepezil hydrochloride form III, C24H29NO3⋅HCl

The crystal structure of donepezil hydrochloride, form III, has been solved with FOX using laboratory powder diffraction data previously submitted to and published in the Powder Diffraction File. Rietveld refinement with GSAS yielded monoclinic lattice parameters of a = 14.3662(9) Å, b = 11.8384(6) Å, c = 13.5572(7) Å, and β = 107.7560(26)° (C24H30ClNO3, Z = 4, space group P21/c). The Rietveld-refined structure was compared to a density functional theory (DFT)-optimized structure, and the structures exhibit excellent agreement. Layers of donepezil molecules parallel to the (101) planes are maintained by columns of chloride anions along the b-axis, where each chloride anion hydrogen bonds to three donepezil molecules each.

Contribution of Nitrogen Heteroatom to Anion-π Interaction of N-heterocyclic Anthracene C14-2mH10-2mN2m (m = 1, 2, and 3) with Chloride Anion

N-heterocyclic aromatic in anion-π interaction has been playing a crucial role in a host of chemical and biological processes. In the present contribution, several different complexes composed of N-heterocyclic anthracene C14-2mH10-2mN2m (m = 1, 2, and 3) and chloride anion are investigated at the atomic level. We find that anion-π interactions are enhanced with the increasing number of N atoms. In addition, positions of nitrogen heteroatoms also have a significant effect on this interaction. Contributions of α, β and γ N atoms are in order of Nβ>Nγ>Nα. Moreover, energy decomposition analysis indicates that electrostatic interactions are the dominant stabilizing forces when chloride anion locates above aromatic ring, while the influence of other terms becomes significant when chloride anion deviates from aromatic ring. It is worth noting that dispersion forces play an important role in those anion-π interactions.