Mass spectrometric studies of cis‐ and trans‐1a,3‐disubstituted‐1,1‐dichloro‐4‐formyl‐1a, 2,3,4‐tetrahydro‐lH‐azirino[1,2‐a]1,5]benzodiazepines

The mass spectrometric behaviour of four cis‐ and trans‐1a,3‐disubstituted‐1,1‐dichloro‐4‐formyl‐1a,2,3,4‐tetrahydro‐1H‐azirino [1, 2‐a][1,5]benzodiazepines has been studied with the aid of mass‐analysed ion kinetic energy spectrometry and exact mass measurements under electron impact ionization. All compounds show a tendency to eliminate a chlorine atom from the aziridine ring, and then eliminate a neutral propene or styrene from the diazepine ring to yield azirino [1,2‐b][1,3] benzimidazole ions. These azirino [1,2‐a][1,5]‐benzodiazepimes can also eliminate HCl, or Cl plus HCl simultaneously to undergo a ring enlargement rearrangement to yield 1,6‐benzodiazocine ions, which further lose small molecular fragments, propyne or phenylacetylene, with rearrangement to give quinoxaline ions.     

11‐Hydro­xy‐3,3‐di­methyl‐7,12‐dioxo‐3,4,6,6a,7,12,12a,12b‐octa­hydro­benz­[a]­anthracen‐1‐yl acetate

The Diels–Alder reaction between 5‐hydroxy‐1,4‐naphtho­quinone and 5,5‐di­methyl‐3‐vinyl‐1,2‐cyclo­hexa­dienyl acetate by endo addition gives the title compound, C₂₂H₂₂O₅, in 68% yield. This racemic diastereoisomer has the opposite regiochemistry to ochromycinone analogues produced previously and may allow access to a new type of anticancer‐active saqua­yamycin analogue.     

3a‐Phenyl‐2,3,3a,4‐tetrahydro‐1H‐benzo[d]pyrrolo[1,2‐a]imidazol‐1‐one,a potential plant‐growth regulator

Molecules of the title compound, C₁₆H₁₄N₂O, a potential plant‐growth regulator, are linked into chains by intermolecular C=O...H—N hydrogen bonds. These chains are weakly interconnected by π–π stacking interactions to form a three‐dimensional framework. A comparison of the geometric parameters of the title molecule and several related benzimidazoles and pyrrolidones is presented.<!?tpb=22pt>     

Synthesis of [1,2‐a] benzimidazolo‐1,3,5‐triazin‐2‐thione, [1,2‐a] benzimidazolo‐1,3,5‐thiadiazin‐2‐thione, [1,2‐a] benzimidazolo‐1,3,5‐triazin‐2‐amine,and [1,2‐a] benzimidazol‐2‐yl amidrazone

N‐benzimidazol‐2‐yl imidate type 1 reacts with thiourea, carbon disulfide, cyanamide, and hydrazide to give, respectively, [1,2‐a] benzimidazolo‐1,3,5‐triazin‐2‐thione 2 , [1,2‐a] benzimidazolo‐1,3,5‐thiadiazin‐2‐thione 3 , [1,2‐a] benzimidazolo‐1,3,5‐triazin‐2‐amine 4 , and [1,2‐a] benzimidazol‐2‐yl amidrazone 5 with good yields. Structures elucidation of all newly synthesized heterocyclic compounds was based on the data of IR, ¹H NMR, ¹³C NMR, elemental analysis, and MS of some products. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:279–283, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20618     

A One‐Pot Organometallic Route from a 4‐Alkenylpyridine to a 4,4‐Spiro‐Linked Ethyl 1,4‐Dihydropyridine‐1‐carboxylate

In a one‐pot process without isolation of intermediates, (but‐3‐en‐1‐yl)pyridine ( 13 ) is treated sequentially with dicyclohexylborane, trimethylaluminium, and ethyl carbonochloridate yielding ethyl 1,4‐dihydro‐4,4‐(tetramethylene)pyridine‐1‐carboxylate (=ethyl 8‐azaspiro[4.5]deca‐6,9‐diene‐8‐carboxylate; 2 ) in 46% yield based on starting alkenylpyridine 13 (Scheme 5).     

9‐Phenyl‐3,4,4a,9a‐tetrahydrotri­ptycene and 9‐phenyl‐1,2,3,4,4a,9a‐hexa­hydro­triptycene

The structure of 9‐phenyl‐3,4,4a,9a‐tetra­hydro­triptycene, C₂₆H₂₂, (I), exhibits regiochemistry consistent with a stepwise mechanism for its formation from photo­cyclo­addition of 1,3‐cyclo­hexa­diene and 9‐phenyl­anthracene. Bond distances involving the bridgehead C atoms are similar in (I) and the hydrogenated derivative, 9‐phenyl‐1,2,3,4,4a,9a‐hexa­hydro­triptycene, C₂₆H₂₄, (II), with bonds to the quaternary‐C atoms exhibiting significant elongation [1.581 (2) Å in (I) and 1.585 (2) Å in (II)]. The molecular geometry precludes significant σ–π overlap between the phenyl groups and the interannular bonds in both compounds, indicating that the origin of the bond lengthening is steric in nature.     

Solvent‐Vapor‐Induced Reversible Single‐Crystal‐to‐Single‐Crystal Transformation of a Triphosphaazatriangulene‐Based Metal–Organic Framework

A triphosphaazatriangulene (H₃L) was synthesized through an intramolecular triple phospha‐Friedel–Crafts reaction. The H₃L triangulene contains three phosphinate groups and an extended π‐conjugated framework, which enables the stimuli‐responsive reversible transformation of [Cu(HL)(DMSO)?(MeOH)]_n, a 3D‐MOF that exhibits reversible sorption characteristics, into (H₃L?0.5 [Cu₂(OH)₄?6 H₂O] ?4 H₂O), a 1D‐columnar assembled proton‐conducting material. The hydrophilic nature of the latter resulted in a proton conductivity of 5.5×10^?3 S cm^?1 at 95 % relative humidity and 60 °C.     

Synthesis of 1,3,3a,5‐tetraaryl‐3a,4,5,6‐tetrahydro‐3H‐1,2,4‐triazolo[4,3‐a] [1,5]benzodiazepines

A series of 3a,5‐diaryl‐1,3‐diphenyl‐3a,4,5,6‐tetrahydro‐3H‐1,2,4‐triazolo[4,3‐a][1,5]benzo‐diazepines was synthesized by the cycloaddition reactions of 2,4‐diaryl‐2,3‐dihydro‐1H‐1,5‐benzo‐diazepines and N‐phenylbenzonitrileimine generated from N‐phenylbenzenecarbohydrazonic chloride in the presence of triethylamine in anhydrous tetrahydrofuran. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:557–559, 2001     

7‐Hydroxy‐5‐methoxy‐6,8‐dimethylflavanone: a natural flavonoid

The title flavonoid [systematic name: (2S)‐7‐hydroxy‐5‐methoxy‐6,8‐dimethyl‐2‐phenyl‐3,4‐dihydrochromen‐4(2H)‐one], C₁₈H₁₈O₄, displays statistical conformational disorder, with three conformations of the molecule involving three orientations of the phenyl ring and two orientations of the fused heterocyclic ring. The conformational disorder is correlated with the isomerization equilibrium between the flavanone and chalcone forms. The conformational behaviour has a potential impact on the biological activity of this class of compounds. Moreover, π stacking interactions at van der Waals distances are present between the aromatic rings of chroman‐4‐one groups of symmetry‐related molecules. Apart from these π–π interactions, molecules are linked by strong O—H...O hydrogen bonds between hydroxy and carbonyl groups.     

l‐Isoleucyl‐l‐asparagine 1.094‐hydrate: a hybrid hydrogen‐bonding pattern

The title compound, C₁₀H₂₀N₃O₄·1.094H₂O, crystallizes with two dipeptide molecules in the asymmetric unit, each participating in two head‐to‐tail chains with hydrogen bonds between the terminal amino and carboxylate groups. As with many other dipeptides, the resulting structure is divided into distinct layers, but as the amide groups of the two peptide molecules participate in different types of interaction, the observed hydrogen bonds within a peptide main‐chain layer (as distinct from the side‐chain/solvent regions) cannot adapt to any of the four basic patterns observed previously for dipeptides. Instead, a rare hybrid pattern is formed.     

Ethyl 1,4‐Dihydro‐4‐oxo‐1,8‐naphthyridine‐3‐carboxylates by a Tandem SNAr‐Addition‐Elimination Reaction

A series of N‐substituted 1,4‐dihydro‐4‐oxo‐1,8‐naphthyridine‐3‐carboxylate esters has been prepared in two steps from ethyl 2‐(2‐chloronicotinoyl)acetate. Treatment of the β‐ketoester with N,N‐dimethylformamide dimethyl acetal in N,N‐dimethylformamide (DMF) gave a 95% yield of the 2‐dimethylaminomethylene derivative. Subsequent reaction of this β‐enaminone with primary amines in DMF at 120^oC for 24 h then afforded the target compounds in 47–82% yields by a tandem S_NAr‐addition‐elimination reaction. Synthetic and procedural details as well as a mechanistic rationale are presented.     

Toughening of a propylene‐b‐(ethylene‐co‐propylene) copolymer by a plastomer

Several blends, covering the entire range of compositions, of a metallocenic ethylene‐1‐octene copolymer (CEO) with a multiphasic block copolymer, propylene‐b‐(ethylene‐co‐propylene) (CPE) [composed of semicrystalline isotactic polypropylene (iPP) and amorphous ethylene‐co‐propylene segments], have been prepared and analyzed by differential scanning calorimetry, X‐ray diffraction, optical microscopy, stress‐strain and microhardness measurements, and dynamic mechanical thermal analysis. The results show that for high CEO contents, the crystallization of the iPP component is inhibited and slowed down in such a way that it crystallizes at much lower temperatures, simultaneously with the crystallization of the CEO crystals. The mechanical results suggest very clearly the toughening effect of CEO as its content increases in the blends, although it is accompanied by a decrease in stiffness. The analysis of the viscoelastic relaxations displays, first, the glass transition of the amorphous blocks of CPE appearing at around 223 K, which is responsible for the initial toughening of the plain CPE copolymer in relation to iPP homopolymer. Moreover, the additional toughening due to the addition of CEO in the blends is explained by the presence of the β relaxation of CEO that appears at about 223 K. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1869–1880, 2002     

Construction of a High‐Mannose‐Type Glycan Library by a Renewed Top‐Down Chemo‐Enzymatic Approach

A comprehensive method for the construction of a high‐mannose‐type glycan library by systematic chemo‐enzymatic trimming of a single Man9‐based precursor was developed. It consists of the chemical synthesis of a non‐natural tridecasaccharide precursor, the orthogonal demasking of the non‐reducing ends, and trimming by glycosidases, which enabled a comprehensive synthesis of high‐mannose‐type glycans in their mono‐ or non‐glucosylated forms. It employed glucose, isopropylidene, and N‐acetylglucosamine groups for blocking the A‐, B‐, and C‐arms, respectively. After systematic trimming of the precursor, thirty‐seven high‐mannose‐type glycans were obtained. The power of the methodology was demonstrated by the enzymatic activity of human recombinant N‐acetylglucosaminyltransferase‐I toward M7–M3 glycans, clarifying the substrate specificity in the context of high‐mannose‐type glycans.     

(+)‐2‐(1,2,3,4,4a,5,6,7‐Octa­hydro‐4a,8‐di­methyl‐7‐oxo‐2‐naphthyl)­propionic acid: catemeric hydrogen bonding in a bicyclic sesquiterpenoid keto acid

The title compound, C₁₅H₂₂O₃, derived from a naturally occurring sesquiterpenoid, has two mol­ecules in the asymmetric unit, differing principally in the rotational conformation of the carboxyl group. Each species aggregates separately as a carboxyl‐to‐ketone hydrogen‐bonding catemer [O?O = 2.752 (4) and 2.682 (4) Å, and O—H?O = 161 (4) and 168 (4)°], producing two crystallographically independent single‐strand hydrogen‐bonding helices, with opposite end‐to‐end orientations, passing through the cell in the b direction. Three intermolecular C—H?O=C close contacts exist for the ketone.     

2,3,3a,4,5a,6,7,8‐Octa­hydro‐5a‐methyl‐6,9‐methano‐1H,9H‐5‐oxa‐4‐aza­cyclo­penta­[c]­indene

The regio‐ and stereochemistry of the title compound, C₁₂H₁₅NO, has been established by X‐ray analysis. The molecular dimensions are normal.     

Preparation of 5‐methyl‐2‐sulfanyl‐7h‐1,3,4‐thiadiazolo[3,2‐a]‐pyrimidin‐7‐ones

7H‐1,3,4‐Thiadiazolo[3,2‐a]pyrimidin‐7‐ones can be prepared by the acylation of 5‐amino‐1,3,4‐thiadiazoles with diketene and subsequent ring closure (dehydration). Whereas arylthio substituents (SC₆H₅) can be introduced in 2‐position by the replacement of Br, alkylthio groups (SC₂H₅) have to be already presentin the starting 5‐amino‐1,3,4‐thiadiazole. The ambident nucleophile 2‐thiazolidinethione reacts in the Br substitution reaction on the N atom.