3,4‐Diethyl‐2,5‐dihydro‐1H‐pyrrole‐2,5‐dione

In the crystal structure of the title compound, C₈H₁₁NO₂, three distinct mol­ecules are present in the asymmetric unit. The mol­ecules are organized in two different hydrogen‐bonded tapes, which form a complex layered structure. A structural comparison with the crystal structures of related maleimide derivatives unravels a stepwise evolution of morphological complexity with increasing mol­ecular complexity for this class of compounds.     

New 7‐phosphanorbornenes derived from 2‐methyl‐1‐phenyl‐ and 1‐cyclohexyl‐3‐ methyl‐2,5‐dihydro‐1H‐phosphole 1‐oxides

Novel 7‐phosphanorbornene derivatives, such as 4, 5, 10 , and 11 were synthesized utilizing 1‐phenyl‐2‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 1 ) and 1‐cyclohexyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxide ( 7 ) as the starting materials. Products 4 and 10 were prepared by trapping the corresponding phosphole oxide intermediates ( 3 and 9 , respectively) by N‐phenylmaleimide, while 5 and 11 were obtained by the dimerization of 3 and 9 , respectively. The trapping reaction was studied in details; on one hand, bromo‐2,3‐dihydro‐1H‐phosphole oxides ( 6‐1 and 6‐2 ) were pointed out as the intermediates, on the other hand, the trapping reaction was optimized. Bri‐ dged P‐heterocycles 4, 5, 10 , and 11 were tested in the fragmentation‐related phosphorylation of methanol. Hydrogenation of phosphanorbornenes 4 and 5 led to the corresponding phosphanorbornanes ( 12 and 14 , respectively) and to a reductive type of retro cycloaddition. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:320–326, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20097     

The Synthesis of N,N‐Bis(dialkoxyphosphinoylmethyl)‐ and N,N‐Bis(diphenylphosphinoylmethyl)glycine Esters by the Microwave‐Assisted Double Kabachnik–Fields Reaction

The condensation of a glycine ester, two equivalents of paraformaldehyde, and the same quantity of a dialkyl phosphite or diphenylphosphine oxide afforded the title compounds as new bis(phospha‐Mannich) products under microwave (MW) conditions at 100°C. The dialkoxyphosphinoylmethyl derivatives were synthesized under solvent‐free conditions, whereas the diphenylphosphinoylmethyl derivatives were synthesized in acetonitrile solution. Comparative thermal experiments showed the beneficial role of MW in respect of efficiency.     

Energetic Salts Based on Monoanions of N,N‐Bis(1H‐tetrazol‐5‐yl)amine and 5,5′‐Bis(tetrazole)

High‐density energetic salts that contain nitrogen‐rich cations and the 5‐(tetrazol‐5‐ylamino)tetrazolate (HBTA^?) or the 5‐(tetrazol‐5‐yl)tetrazolate (HBT^?) anion were readily synthesized by the metathesis reactions of sulfate salts with barium compounds, such as bis[5‐(tetrazol‐5‐ylamino)tetrazolate] (Ba(HBTA)₂), barium iminobis(5‐tetrazolate) (BaBTA), or barium 5,5′‐bis(tetrazolate) (BaBT) in aqueous solution. All salts were fully characterized by IR spectroscopy, multinuclear (¹H, ¹³C, ¹⁵N) NMR spectroscopy, elemental analyses, density, differential scanning calorimetry (DSC), and impact sensitivity. Ba(HBTA)₂ ? 4 H₂O crystallizes in the triclinic space group P$\bar 1$ , as determined by single‐crystal X‐ray diffraction, with a density of 2.177 g cm^?3. The densities of the other organic energetic salts range between 1.55 and 1.75 g cm^?3 as measured by a gas pycnometer. The detonation pressure (P) values calculated for these salts range from 19.4 to 33.6 GPa, and the detonation velocities (ν_D) range from 7677 to 9487 m s^?1, which make them competitive energetic materials. Solid‐state ¹³C NMR spectroscopy was used as an effective technique to determine the structure of the products that were obtained from the metathesis reactions of biguanidinium sulfate with barium iminobis(5‐tetrazolate) (BaBTA). Thus, the structure was determined as an HBTA salt by the comparison of its solid‐state ¹³C NMR spectroscopy with those of ammonium 5‐(tetrazol‐5‐ylamino)tetrazolate (AHBTA) and diammonium iminobis(5‐tetrazolate) (A₂BTA).     

Synthesis of N,N‐Bis(dialkoxyphosphinoylmethyl)‐ and N,N‐Bis(diphenylphosphinoylmethyl)‐β‐ and γ‐amino acid Derivatives by the Microwave‐Assisted Double Kabachnik–Fields Reaction

The title compounds were synthesized by the microwave‐assisted, mostly solvent‐free bis Kabachnik–Fields condensation of β‐alanine and γ‐aminobutyric acid or their esters with formaldehyde and >P(O)H species, such as dialkyl phosphites and diphenylphosphine oxide.     

4‐(2,5‐Dioxo‐2,5‐dihydro‐1H‐pyrrol‐1‐yl)benzoic acid: X‐ray and DFT‐calculated structure

In the title compound, C₁₁H₇NO₄, there is a dihedral angle of 45.80 (7)° between the planes of the benzene and maleimide rings. The presence of O—H...O hydrogen bonding and weak C—H...O interactions allows the formation of R₃³(19) edge‐connected rings parallel to the (010) plane. Structural, spectroscopic and theoretical studies were carried out. Density functional theory (DFT) optimized structures at the B3LYP/6–311 G(d,p) and 6–31++G(d,p) levels are compared with the experimentally determined molecular structure in the solid state. Additional IR and UV theoretical studies allowed the presence of functional groups and the transition bands of the system to be identified.     

Synthesis and antimicrobial activity of 2‐substituted‐2,3‐dihydro‐5‐propoxy‐1H‐1,3,2‐benzodiazaphosphole 2‐Oxides

Several 2‐alkylcarbamato/thiocarbamato/aryloxy/trichloromethyl‐2,3‐dihydro‐5‐propoxy‐1H‐1,3,2‐benzodiazaphosphole 2‐oxides ( 4 and 6 ) were synthesised by reacting 4‐propoxy‐o‐phenylenediamine ( 1 ) with various N‐dichlorophosphinyl carbamates ( 3 ), aryl phosphorodichloridates ( 5a‐f ) and trichloromethyl phosphonic dichloride ( 5g ) in the presence of triethylamine at 45‐65 °C. Their ir, ¹H, ¹³C, ³¹P nmr and mass spectral data are discussed. The compounds were screened for antifungal activity against Curvularia lunata and Aspergillus niger and for antibacterial activity against Bacillus subtilis and Escherichia coli. Most of these compounds exhibited moderate activity in the assays.     

Synthesis of Functionalized Polynorbornanes Employing 2,5‐Bis(trifluoromethyl)‐1,3,4‐oxadiazole

Cycloaddition reaction of 2,5‐bis(trifluoromethyl)‐1,3,4‐oxadiazole with strained olefinic bonds of norbornenes was used to synthetize functionalized polynorbornanes. This simple, one step procedure was more effective when reaction was carried out by classical heating, in comparison to microwave‐assisted reactions. Various functional groups were stable in the reaction conditions (ester, imide, phthalimide, piperidyl, and carboxylic acid), whereas anhydride, N‐Boc, or TMS functionalities do not withstand reaction conditions.     

Synthesis and Characterization of Bis(2‐iminopyrrolyl) Iron(II) Complexes by N–H Bond Activation

The reactions of 2‐iminopyrroles 1 – 3 with Fe(PMe₃)₄ afforded the N–H activated bis(2‐iminopyrrolyl) iron(II) complexes 4 – 6 . The structures of compounds 4 – 6 were determined by single‐crystal X‐ray diffraction. The formation mechanism of complexes 4 – 6 was discussed.     

Synthesis,structure, and antibacterial evaluation of new N‐substituted‐3‐amino‐ 5‐oxo‐4‐phenyl‐2,5‐dihydro‐1H‐pyrazole‐1‐carbothioamides

Novel N‐substituted‐3‐amino‐5‐oxo‐4‐phenyl‐2,5‐dihydro‐1H‐pyrazole‐1‐carbothioamide derivatives were synthesized by means of two methods. First is the cyclization reaction of 1‐(cyanophenyl)acetyl‐4‐substituted thiosemicarbazide, and the second one is reaction of cyanophenyl acetic acid hydrazide with isothiocyanate. Structures of new compounds were confirmed by elemental analysis, ¹H NMR, and X‐ray diffraction analysis. Biological evaluation showed that some of them possess promising antibacterial activities. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:215–221, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20598     

Synthesis of 3,4‐dihydro‐1(2H)‐isoquinolinonesxs

Approaches toward the preparative‐scale synthesis of target 3,4‐dihydro‐1(2H)‐isoquinolinones 1–3 are presented. Compounds 1 and 2 were prepared via a Schmidt rearrangement on easily obtained indanone precursors, but in low overall yield. A better method to make this class of compounds is exemplified by the large‐scale synthesis of 2 via a Curtius rearrangement sequence. Thus, high‐temperature thermal cyclization of an in situ formed styryl isocyanate from precursor 8 in the presence of tributylamine gave the corresponding 1(2H)‐isoquinolinone ( 9 ). Catalytic hydrogenation of 9 provided the desired 3,4‐dihydro‐5‐methyl‐1(2H)‐isoquinolinone ( 2 ) in 65 % overall yield. Similar reduction of a commercially available 5‐hydroxy‐1(2H)‐isoquinolinone precursor 10 followed by an O ‐alkylation/amination sequence gave target 3 in good overall yield. The route proceeding via the Curtius rearrangement is recommended for large scale synthesis of other 3,4‐dihydro‐1(2H)‐isoquinolinones. Only when deactivating substituents or sensitive functionality within the benzenoid ring render the high temperature ring closure of the intermediate isocyanate inefficient might a Schmidt rearrangement protocol be the method of choice.     

Synthesis of 2‐Aryl‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐2,5‐dihydro‐1H‐pyrrole‐3‐carboxylates by the Reaction between Hydrazones,Acetylenedicarboxylates, and 1‐Aryl‐N,N′‐bis(arylmethylidene)methanediamines

An efficient approach for the preparation of functionalized 2‐aryl‐2,5‐dihydro‐5‐oxo‐4‐[2‐(phenylmethylidene)hydrazino]‐1H‐pyrroles is described. The four‐component reaction between aldehydes, NH₂NH₂?H₂O, dialkyl acetylenedicarboxylates, and 1‐aryl‐N,N′‐bis(arylmethylidene)methanediamines proceeds in EtOH under reflux in good‐to‐excellent yields (Scheme 1). The structures of 4 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS, and, in the case of 4f , by X‐ray crystallography). A plausible mechanism for this type of reaction is proposed (Scheme 2).     

Synthesis and thermolysis of the 2,3‐dihydro‐1H‐pyrole‐2,3‐diones,pseudopericyclic reactions of formyl(N‐phenylimidoyl)ketene: Experimental data and PM3 calculations

The reactions of the 2,3‐dihydro‐1H‐furan‐2,3‐dione 1 with Schiff bases 2a‐f at 60–70°C furnish the corresponding 2,3‐dihydro‐1H‐pyrole‐2,3‐diones 3a‐f . The heating of 3a‐d afforded the corresponding 4‐methoxybenzoyl(N‐arylimidoyl)k:etenes 4a‐d as intermediates which undergo a very facile cyclization to quinoline‐4‐ones 5a‐d . According to our PM3 calculations, fragmentation of 4‐formyl‐2,3‐dihydro‐1H‐pyrole‐2,3‐dione and 1,4‐cyclization of formyl(N‐phenylimidoyl)k:etene IN1 to azetin‐2‐one IN2 and oxe‐tone IN3 are pseudopericyclic reactions with two orbital connections, proceed via planar transition structures. Due to to the possibility of syn and anti conformations of the imine phenyl, there are eight E/Z‐iso‐mers of IN1 . In addition, we have also calculated reaction mechanism of formation of quinoline‐4‐ones by the PM3 method.     

Racemic and chiral 1‐[N‐(chloro­acetyl)carbamoylamino]‐2,3‐dihydro‐1H‐inden‐2‐yl chloroacetate

In the racemic crystals of (1S,2R)‐ or (1R,2S)‐1‐[N‐(chloro­acetyl)­carbamoyl­amino]‐2,3‐di­hydro‐1H‐inden‐2‐yl chloro­acetate, C₁₄H₁₄Cl₂N₂O₄, (I), the enantiomeric mol­ecules form a dimeric structure via the N—H?O cyclic hydrogen bond of the carbamoyl moieties. In the chiral crystals of (—)‐(1S,2R)‐1‐[N‐(chloro­acetyl)­carbamoyl­amino]‐2,3‐di­hydro‐1H‐inden‐2‐yl chloro­acetate, C₁₄H₁₄Cl₂N₂O₄, (II), the N—­H?O intermolecular hydrogen bond forms a zigzag chain around the twofold screw axis. The melting points and calculated densities of (I) and (II) are 446 and 396 K, and 1.481 and 1.445 Mg m^?3, respectively.     

Synthesis of 2‐Aryl‐2,3‐dihydro‐3‐sulfanyl‐1H‐isoindol‐1‐ones by Pummerer‐Type Cyclization of N‐Aryl‐2‐(sulfinylmethyl)benzamides

An efficient method for the synthesis of 2‐aryl‐2,3‐dihydro‐3‐sulfanyl‐1H‐isoindol‐1‐ones 1 via Pummerer‐type cyclization of N‐aryl‐2‐(sulfinylmethyl)benzamides 2 is described. Thus, treatment of these sulfinyl‐benzamides 2 , easily prepared from 2‐(bromomethyl)benzoates 3 in three steps, with Ac₂O at ca. 100° resulted in the formation of the desired isoindolones 1 in generally good yields.     

Photocycloisomerization of Boc‐Protected 5‐Alkenyl‐2,5‐dihydro‐1H‐ pyrrol‐2‐ones

On irradiation (254 nm), the newly synthesized Boc‐protected 5‐alkenyl‐2,5‐dihydro‐1H‐pyrrol‐2‐ones 13 undergo regioselective intramolecular [2+2] photocycloadditions. While the allyl derivatives 13a – 13c afford mainly azatricyclo[3.3.0.0^2,7]octanones, i.e., crossed cycloadducts, the butenyl‐ and pentenyl‐substituted compounds 13d and 13e isomerize preferentially to straight cycloadducts.     

Synthesis and Biological Activities of Novel 6‐Alkylamino‐11,12‐dihydro‐11‐arylbenzo[c]phenanthridine Derivatives

A series of novel benzo[c]phenanthridine derivatives 2a , 2b , 2c , 2d , 2e , 2f , 2g , 2h , 2i , 2j , 2k , 2l , 2m and 3a , 3b , 3c , 3d , 3e , 3f bearing an alkylamino side chain at their 6‐position were synthesized. All of the target compounds were confirmed by ¹H NMR, ¹³C NMR, and HRMS, and some of them were also characterized by IR and ¹⁹F NMR. The preliminary bioassays showed that the target compounds displayed fungicidal activities; for example, compound 2l showed 60.0% and 70.0% inhibitive activity against Alternaria solani and Cercospora arachidicola at 50 mg/L, respectively, and some compounds also displayed plant growth‐regulating activities.     

Enantioselective Addition of Cyclic Enol Silyl Ethers to 2‐Alkenoyl‐Pyridine‐N‐Oxides Catalysed by CuII–Bis(oxazoline) Complexes

Asymmetric reactions involving (E)‐3‐aryl‐1‐(pyridin‐2‐yl‐N‐oxide)prop‐2‐en‐1‐ones and cyclic enol silyl ethers show good yields and excellent enantioselectivities (up to 99.9 % ee) when catalysed by bis(oxazoline)–Cu^II complexes. Different reaction pathways can be followed by different enol silyl ethers: with 2‐(trimethylsilyloxy)furan, a Mukaiyama–Michael adduct is obtained, whereas a hetero Diels–Alder cycloadduct was formed by using (1,2‐dihydronaphthalen‐4‐yloxy)trimethylsilane. In the latter reaction, the absolute configuration of the product is consistent with a reagent approach to the less hindered Re face of the coordinated substrate in the reactive complex.     

Synthesis of Imidazole Derivatives Using 2‐Unsubstituted 1H‐Imidazole 3‐Oxides

The reaction of 1,4,5‐trisubstituted 1H‐imidazole 3‐oxides 1 with Ac₂O in CH₂Cl₂ at 0 – 5° leads to the corresponding 1,3‐dihydro‐2H‐imidazol‐2‐ones 4 in good yields. In refluxing Ac₂O, the N‐oxides 1 are transformed to N‐acetylated 1,3‐dihydro‐2H‐imidazol‐2‐ones 5 . The proposed mechanisms for these reactions are analogous to those for N‐oxides of 6‐membered heterocycles (Scheme 2). A smooth synthesis of 1H‐imidazole‐2‐carbonitriles 2 starting with 1 is achieved by treatment with trimethylsilanecarbonitrile (Me₃SiCN) in CH₂Cl₂ at 0 – 5° (Scheme 3).