7‐Iodo‐5‐aza‐7‐deazaguanine: Syntheses of Anomeric D‐ and L‐Configured 2‐Deoxyribonucleosides

Iodination of N²‐isobutyryl‐5‐aza‐7‐deazaguanine ( 7 ) with N‐iodosuccinimide (NIS) gave 7‐iodo‐N²‐isobutyryl‐5‐aza‐7‐deazaguanine ( 8 ) in a regioselective reaction (Scheme 1). Nucleobase‐anion glycosylation of 8 with 2‐deoxy‐3,5‐di‐O‐toluoyl‐α‐D ‐ or α‐L ‐erythro‐pentofuranosyl chloride furnished anomeric mixtures of D ‐ and L ‐nucleosides. The anomeric D ‐nucleosides were separated by crystallization to give the α‐D ‐anomer and β‐D ‐anomer with excellent optical purity. Deprotection gave the 7‐iodo‐5‐aza‐7‐deazaguanine 2′‐deoxyribonucleosides 3 (β‐D ; ≥99% de) and 4 (α‐D ; ≥99% de). The reaction sequence performed with the D ‐series was also applied to L ‐nucleosides to furnish compounds 5 (β‐L ; ≥99% de) and 6 (α‐L ; ≥95% de).     

Asymmetric anionic polymerizations of 7‐cyano‐7‐alkoxycarbonyl‐1,4‐benzoquinone methides

Asymmetric anionic polymerizations of 7‐cyano‐7‐alkoxycarbonyl‐1,4‐benzoquinone methides ( 1 ) with various alkoxy groups were performed using chiral initiators such as lithium isopropylphenoxide (ⁱPrPhOLi)/(S)‐(–)‐2,2′‐isopropylidene‐bis(4‐phenyl‐2‐oxazoline) ((–)‐PhBox) and lithium isopropylphenoxide (ⁱPrPhOLi)/(–)‐sparteine ((–)‐Sp) to investigate the effect of the alkoxy groups of alkoxycarbonyl substituent in the monomers 1 and chiral ligands of chiral initiators on the control of chiral center in the formation of polymers. Molar optical rotation values of the polymers were significantly dependent upon alkoxy groups, and the polymers with higher molar optical rotation were obtained in monomers with primary alkoxy groups. The asymmetric anionic oligomerizations of the quinone methides having methoxy( 1a ), ethoxy( 1b ), and n‐propoxy( 1c ) groups with chiral initiators were carried out. Both 1‐mers and 2‐mers were isolated and their optical resolutions were performed to determine the extent of stereocontrol. High stereoselectivity was observed at the propagation reaction, but not at the initiation reaction. The effect of the counterion on the control of chiral center in the formation of the polymer was investigated in the asymmetric anionic polymerizations of 1b with ⁱPrPhOM(M = Li, Na, K)/(–)‐Sp and ⁱPrPhOM(M = Li, Na, K)/(–)‐PhBox initiators and discussed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Herstellung von 1,2,4‐Trithiolan‐, 1,2,4,5‐Tetrathian‐ sowie 1,2,3,5,6‐Pentathiepan‐S‐oxiden und deren Reaktionen mit (Ph3P)2Pt(η2‐C2H4). Kristallstrukturanalyse von 3,3,5,5‐Tetraphenyl‐1,2,4‐trithiolan‐1‐oxid

Metal Complexes of Functionalized Sulfur‐containing Ligands. XVII Synthesis of S ‐Oxides of 1,2,4‐Trithiolane, 1,2,4,5‐Tetrathiane as well as 1,2,3,5,6‐Pentathiepane, and their Reactions with (Ph₃P)₂Pt(η²‐C₂H₄). X‐Ray Structure Analysis of 3,3,5,5‐Tetraphenyl‐1,2,4‐trithiolane 1‐oxide 3,3,5,5‐Tetraphenyl‐1,2,4‐trithiolan ( 1 ) was oxidized using m‐chloroperbenzoic acid to give, selectively, the 3,3,5,5‐tetraphenyl‐1,2,4‐trithiolane 1‐oxide ( 2 ). 2 was characterized structurally. The reaction of octamethyl tetrathiadispiro[3.2.3.2]dodecane‐2,9‐dione ( 3 ) with trifluoroperacetic acid at –50 °C yielded the corresponding 5‐oxide 4 . Oxidation of octamethyl pentathiadispiro[3.3.3.2]tridecane‐2,9‐dione ( 5 ) with m‐chloroperbenzoic acid at 0 °C gave the 12‐oxide 6 . Treatment of 2 with two equivalents of (Ph₃P)₂Pt(η²‐C₂H₄) ( 7 ) afforded a mixture (1 : 1) of the complexes (Ph₃P)₂PtSCPh₂S ( 8 ) and (Ph₃P)₂Pt(η²‐Ph₂C=S=O) ( 9 ), respectively.     

7‐Substituted 7‐Deaza‐2′‐deoxyadenosines and 8‐Aza‐7‐deaza‐2′‐deoxyadenosines: Fluorescence of DNA‐Base Analogues Induced by the 7‐Alkynyl Side Chain

7‐Alkynylated 7‐deazaadenine (pyrrolo[2,3‐d]pyrimidin‐4‐amine) 2′‐deoxyribonucleosides show strong fluorescence which is induced by the 7‐alkynyl side chain (Table 3). A large Stokes shift with an emission around 400 nm is observed when the compound is irradiated at 280 nm. The solvent dependence indicates the formation of a charged transition state. The fluorescence appears when the triple bond is in conjugation with the heterocyclic base. Electron‐donating substituents at the triple bond increase the fluorescence, while electron‐withdrawing residues reduce it. In comparison, the 7‐alkynylated 8‐aza‐7‐deazaadenine (pyrazolo[3,4‐d]pyrimidin‐4‐amine) 2′‐deoxyribonucleosides are rather weakly fluorescent (Table 4). Quantum yields and fluorescence decay times are measured. The synthesis of the 7‐alkynylated 7‐deaza‐2′‐deoxyadenosines and 8‐aza‐7‐deaza‐2′‐deoxyadenosines was performed with 7‐deaza‐2′‐deoxy‐7‐iodoadenosine ( 6 ) or 8‐aza‐7‐deaza‐2′‐deoxy‐7‐iodoadenosine ( 22 ) as starting materials and employing the Pd⁰‐catalyzed cross‐coupling reaction with the corresponding alkynes (Schemes 1, 4, and 5). Catalytic hydrogenation of the side chain of the unsaturated nucleosides 5 and 17 afforded the 7‐alkyl derivatives 18 and 19 , respectively, which do not show significant fluorescence (Scheme 2).     

Synthesis and Characterization of New 7‐Substituted 6,14‐Ethenomorphinane Derivatives: N‐{5‐[(5α,7α)‐4,5‐Epoxy‐3,6‐dimethoxy‐17‐methyl‐6,14‐ethenomorphinan‐7‐yl]‐1,3,4‐oxadiazol‐2‐yl}arenamines

In this study, (5α,7α)‐4,5‐epoxy‐3,6‐dimethoxy‐17‐methyl‐6,14‐ethenomorphinan‐7‐carboxylic acid hydrazide ( 5 ) was synthesized by the condensation of methyl (5α,7α)‐4,5‐epoxy‐3,6‐dimethoxy‐17‐methyl‐6,14‐ethenomorphinan‐7‐carboxylate ( 4 ) with NH₂NH₂⋅H₂O. The (5α,7α)‐4,5‐epoxy‐3,6‐dimethoxy‐17‐methyl‐6,14‐ethenomorphinan‐7‐carboxylic acid 2‐[(arylamino)carbonyl]hydrazides 6a – 6q were prepared by the reaction of 5 with corresponding substituted aryl isocyanates, and the N‐{5‐[(5α,7α)‐4,5‐epoxy‐3,6‐dimethoxy‐17‐methyl‐6,14‐ethenomorphinan‐7‐yl]‐1,3,4‐oxadiazol‐2‐yl}arenamines 7a – 7q were obtained via the cyclization reaction of 6a – 6q in the presence of POCl₃. The synthesized compounds have a rigid morphine structure, including the 6,14‐endo‐etheno bridge and the 5‐(arylamino)‐1,3,4‐oxadiazol‐2‐yl residue at C(7) adopting the (S)‐configuration (7α). The structures of the compounds were confirmed by high‐resolution mass spectrometry (HR‐MS) and various spectroscopic methods such as FT‐IR, ¹H‐NMR, ¹³C‐NMR, APT, and 2D‐NMR (HETCOR, COSY, INADEQUATE).     

7‐Halogenated 7‐Deazapurine 2′‐Deoxyribonucleosides Related to 2′‐Deoxyadenosine, 2′‐Deoxyxanthosine,and 2′‐Deoxyisoguanosine: Syntheses and Properties

A series of 7‐fluorinated 7‐deazapurine 2′‐deoxyribonucleosides related to 2′‐deoxyadenosine, 2′‐deoxyxanthosine, and 2′‐deoxyisoguanosine as well as intermediates 4b – 7b, 8, 9b, 10b , and 17b were synthesized. The 7‐fluoro substituent was introduced in 2,6‐dichloro‐7‐deaza‐9H‐purine ( 11a ) with Selectfluor (Scheme 1). Apart from 2,6‐dichloro‐7‐fluoro‐7‐deaza‐9H‐purine ( 11b ), the 7‐chloro compound 11c was formed as by‐product. The mixture 11b / 11c was used for the glycosylation reaction; the separation of the 7‐fluoro from the 7‐chloro compound was performed on the level of the unprotected nucleosides. Other halogen substituents were introduced with N‐halogenosuccinimides ( 11a → 11c – 11e ). Nucleobase‐anion glycosylation afforded the nucleoside intermediates 13a – 13e (Scheme 2). The 7‐fluoro‐ and the 7‐chloro‐7‐deaza‐2′‐deoxyxanthosines, 5b and 5c , respectively, were obtained from the corresponding MeO compounds 17b and 17c , or 18 (Scheme 6). The 2′‐deoxyisoguanosine derivative 4b was prepared from 2‐chloro‐7‐fluoro‐7‐deaza‐2′‐deoxyadenosine 6b via a photochemically induced nucleophilic displacement reaction (Scheme 5). The pK_a values of the halogenated nucleosides were determined (Table 3). ¹³C‐NMR Chemical‐shift dependencies of C(7), C(5), and C(8) were related to the electronegativity of the 7‐halogen substituents (Fig. 3). In aqueous solution, 7‐halogenated 2′‐deoxyribonucleosides show an approximately 70% S population (Fig. 2 and Table 1).     

Synthesis and Herbicidal Activity of Novel 4‐Acyl‐2,5‐disubstituted‐3‐hydroxypyrazoles and 4‐Arylcarbonyl‐3‐substitutedisoxazol‐5‐ones

Two series of novel 4‐acyl‐2,5‐disubstituted‐3‐hydroxypyrazoles 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h and 4‐arylcarbonyl‐3‐substitutedisoxazol‐5‐ones 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7i were synthesized by the Scotton–Baumann reaction of 2,5‐disubstituted‐2,4‐dihydro‐pyrazol‐3‐ones 1 or 3‐substituted‐4H‐isoxazol‐5‐ones 6 and various acyl chlorides, followed by the Fries rearrangement in the presence of calcium hydroxide and calcium oxide as the catalyst. Their structures were confirmed by IR, ¹H NMR, mass spectroscopy, and elemental analyses. ¹H NMR indicated that compounds 3 existed in enol forms and compounds 7 in keto configurations. The results of preliminary bioassays showed that some of the title compounds 3 and 7 exhibited moderate to good herbicidal activities against Brassica campestris L. at the concentration of 100 mg/L. Isoxazole compounds 7 showed better herbicidal activity against B. campestris L. than pyrazole compounds 3 did at the concentration of 100 mg/L. Moreover, most of the isoxazole compounds displayed higher herbicidal activity against B. campestris L. than Echinochloa crus‐galli. However, these compounds showed weak herbicidal activities at the concentration of 10 mg/L.     

Synthesis of Potential Bioactive Novel 7‐[2‐Hydroxy‐3‐(1,2,3‐triazol‐1‐yl)propyloxy]‐3‐alkyl‐4‐methylcoumarins

A series of 50 novel 7‐[2‐hydroxy‐3‐(1,2,3‐triazol‐1‐yl)propyloxy]‐3‐alkyl‐4‐methylcoumarins had been designed and synthesized in good to excellent yields via Cu(I)‐catalyzed 1,3‐dipolar cycloaddition reaction “click chemistry” of 7‐(3‐azido‐2‐hydroxypropyloxy)‐3‐alkyl‐4‐methylcoumarins with variety of acetylene derivatives. In turn, the precursor compound, that is, 7‐(3‐azido‐2‐hydroxypropyloxy)‐3‐alkyl‐4‐methylcoumarin, was synthesized by condensation of epichlorohydrin with 7‐hydroxy‐3‐alkyl‐4‐methylcoumarins followed by opening of the epoxide ring in the resulted 7‐epoxymethoxy‐3‐alkyl‐4‐methylcoumarins with sodium azide. All the synthesized compounds were unambiguously identified on the basis of their spectral data analyses (IR, ¹H‐NMR, ¹³C‐NMR spectra, and HRMS).     

Metallation reactions. XXXIV. Synthesis of 2‐(1‐hydroxy‐1‐arylethyl)‐1,3‐benzoxathiol‐3‐oxide derivatives

The reaction of benzoxathiole‐3‐oxide with lithiumdiisopropylamide in tetrahydrofuran gave an anion, which was reacted with various aryl‐methyl‐ketones to give 2‐(1‐hydroxy‐1‐arylethyl)‐1,3‐benzoxathiol‐3‐oxide derivatives. The reaction was carried out in different temperature conditions: at ‐88 °C the trans addition stereoisomers to the sulfoxide oxygen atom were the main products.     

固相β-环糊精包结物诱导7-羟基-2-甲氧基-2-甲基色满的不对称合成

研究了室温下间苯二酚和甲基乙烯基酮分别与β-环糊精（ β-CD）形成包结物后的几种不同固相反应,结果表明包结物A（间苯二酚/β-CD）与包结物B（甲基乙烯基酮/β-CD）反应能够很好地得到目的产物,产率及ee值分别为82.8%和78.4%;间苯二酚与包结物B反应仅得到低光学活性产物（ee值为19.5%）;包结物A与甲基乙烯基酮反应却没有得到手性目的产物。以熔点、X-粉末衍射、固相核磁碳谱及ROESY多种方法对所形成的包结物进行了表征,包结物中主客体的比例（1：1）通过¹H NMR (400 MHz)得以确定,文章对固相环加成反应的机制也进行了初步探讨。     

Oligonucleotides Containing 7‐Deaza‐2′‐deoxyinosine as Universal Nucleoside: Synthesis of 7‐Halogenated and 7‐Alkynylated Derivatives,Ambiguous Base Pairing,and Dye Functionalization by the Alkyne–Azide ‘Click’ Reaction

Oligonucleotides containing 7‐deaza‐2′‐deoxyinosine derivatives bearing 7‐halogen substituents or 7‐alkynyl groups were prepared. For this, the phosphoramidites 2b – 2g containing 7‐substituted 7‐deaza‐2′‐deoxyinosine analogues 1b – 1g were synthesized (Scheme 2). Hybridization experiments with modified oligonucleotides demonstrate that all 2′‐deoxyinosine derivatives show ambiguous base pairing, as 2′‐deoxyinosine does. The duplex stability decreases in the order C_d>A_d>T_d>G_d when 2b – 2g pair with these canonical nucleosides (Table 6). The self‐complementary duplexes 5′‐d(F⁷c⁷I‐C)₆, d(Br⁷c⁷I‐C)₆, and d(I⁷c⁷I‐C)₆ are more stable than the parent duplex d(c⁷I‐C)₆ (Table 7). An oligonucleotide containing the octa‐1,7‐diyn‐1‐yl derivative 1g , i.e., 27 , was functionalized with the nonfluorescent 3‐azido‐7‐hydroxycoumarin ( 28 ) by the Huisgen–Sharpless–Meldal cycloaddition ‘click’ reaction to afford the highly fluorescent oligonucleotide conjugate 29 (Scheme 3). Consequently, oligonucleotides incorporating the derivative 1g bearing a terminal C?C bond show a number of favorable properties: i) it is possible to activate them by labeling with reporter molecules employing the ‘click’ chemistry. ii) Space demanding residues introduced in the 7‐position of the 7‐deazapurine base does not interfere with duplex structure and stability (Table 8). iii) The ambiguous pairing character of the nucleobase makes them universal probes for numerous applications in oligonucleotide chemistry, molecular biology, and nanobiotechnology.     

An Efficient One‐pot Three‐component Method for the Synthesis of 5‐Amino‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐7‐aryl‐7H‐thiazolo[3,2‐a]pyridine‐6,8‐dicarbonitriles

A facile, convenient, and adequate method has been developed for the synthesis of novel 5‐amino‐3‐(2‐oxo‐2H‐chromen‐3‐yl)‐7‐aryl‐7H‐thiazolo[3,2‐a]pyridine‐6,8‐dicarbonitriles ( 6 ) by employing 2‐(4‐(2‐oxo‐2H‐chromen‐3‐yl)thiazol‐2‐yl)acetonitrile ( 3 ) as an important precursor. Initially, we have synthesized the target compounds in a stepwise manner and then approached a tandem method to examine the feasibility of one‐pot method. Subsequently, one‐pot three‐component protocol has been established for the synthesis of title compounds by the reaction of 3 with benzaldehyde and malononitrile in refluxing ethanol engender a new six‐membered thiazolo[3,2‐a] pyridine as a hybrid scaffold. Reaction conditions were optimized for this reaction and a broad substrate scope with various aryl and heteroaryl aldehydes make this protocol very practical, attractive, and worthy. Mechanistic aspects for the formation of these compounds were outlined comprehensively. Characterization of these newly synthesized compounds was achieved by means of IR, ¹H NMR, ¹³C NMR, and HRMS.     

Synthesis of a novel bis‐spiroorthoester containing 9,10‐dihydro‐9‐oxa‐10‐phosphaphenantrene‐10‐oxide as a substituent: Homopolymerization and copolymerization with diglycidyl ether of bisphenol A

A new bis‐spiroorthoester‐containing monomer, bis[(1,4,6‐trioxaspiro‐[4.4]‐nonan‐2‐yl)‐methyl] 2‐[10‐(9,10‐dihydro‐9‐oxa‐10‐phosphaphenantrene‐10‐oxide‐10‐yl)] maleate (SOE‐DOPOMA), was synthesized with good yields by an esterification reaction with a hydroxylated spiroorthoester (2‐hydroxymethyl‐1,4,6‐trioxaspiro‐[4.4]‐nonane) and a phosphorus‐containing diacid {2‐[10‐(9,10‐dihydro‐9‐oxa‐10‐phosphaphenantrene‐10‐ oxide‐10‐yl)] maleic acid}, both of which were previously synthesized. SOE‐DOPOMA was characterized with ¹H, ¹³C, and ³¹P NMR spectroscopy. This new spiroorthoester was crosslinked with ytterbium triflate as a cationic initiator. A mixture of SOE‐DOPOMA and diglycidyl ether of bisphenol A was also crosslinked under the same conditions. The curing was studied with differential scanning calorimetry and monitored with Fourier transform infrared spectroscopy. The materials were characterized with differential scanning calorimetry, thermogravimetric analysis, and thermodynamomechanical analysis. The shrinkage effect on cationic crosslinking was assessed with gas pycnometry, and the flame‐retardant properties were determined with limiting oxygen index measurements. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1980–1992, 2007.     

Synthesis and characterization of novel polyimide from bis‐(3‐aminophenyl)‐4‐(trifluoromethyl)phenyl phosphine oxide

A novel diamine, bis‐(3‐aminophenyl)‐4‐(trifluoromethyl)phenyl phosphine oxide (mDA3FPPO), containing phosphine oxide and fluorine moieties was prepared via the Grignard reaction from an intermediate, 4‐(trifluoromethyl)phenyl diphenyl phosphine oxide, that was synthesized from diphenylphosphinic chloride and 4‐(trifluoromethyl)bromobenzene, followed by nitration and reduction. The monomer was characterized by Fourier transform infrared (FTIR), ¹H NMR, ³¹P NMR, ¹⁹F NMR spectroscopies; elemental analysis; melting point measurements; and titration and was used to prepare polyimides with a number of dianhydrides such as pyromellitic dianhydride (PMDA), 5,5′‐[2,2,2‐trifluoro‐1‐(trifluoromethyl)ethyliden]‐bis‐1,3‐isobenzofuranedione (6FDA), 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride (BTDA), and 4,4′‐oxydiphthalic dianhydride (ODPA). Polyimides were synthesized via a conventional two‐step route; preparation of polyamic acids, followed by solution imidization, and the molecular weight were controlled to 20,000 g/mol. Resulting polyimides were characterized by FTIR, NMR, DSC, and intrinsic viscosity measurements. Refractive‐index, dielectric constant, and adhesive properties were also determined. The properties of polyimides were compared with those of polyimides prepared from 1,1‐bis‐(4‐aminophenyl)‐1‐phenyl‐2,2,2‐trifluoroethane (3FDAm) and bis‐(3‐aminophenyl) phenyl phosphine oxide (mDAPPO). The polyimides prepared from mDA3FPPO provided high glass‐transition temperatures (248–311 °C), good thermal stability, excellent solubility, low birefringence (0.0030–0.0036), low dielectric constants (2.9–3.1), and excellent adhesive properties with Cu foils (107 g/mm). © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3335–3347, 2001     

7‐Halogenated 7‐Deaza‐2′‐deoxyxanthine 2′‐Deoxyribonucleosides

The synthesis of the 7‐halogenated derivatives 1b (7‐bromo) and 1c (7‐iodo) of 7‐deaza‐2′‐deoxyxanthosine ( 1a ) is described. A partial Br→I exchange was observed when the demethylation of 6‐methoxy precursor compound 4b was performed with Me₃SiCl/NaI. This reaction is circumvented by the nucleophilic displacement of the MeO group under strong alkaline conditions. The halogenated 7‐deaza‐2′‐deoxyxanthosine derivatives 1b , c show a decreased S‐conformer population of the sugar moiety compared to the nonhalogenated 1a . They are expected to form stronger triplexes when they replace 1a in the 1 ?dA?dT base triplet.     

Revisiting the 7‐Phospanorbornene Family: New P‐Alkyl Derivatives

A series of 1‐alkyl‐3‐methyl‐2,5‐dihydro‐1H‐phosphole oxides were converted to the corresponding phosphole oxides that, by the Diels–Alder reaction with N‐maleimide derivatives or with another unit of phosphole oxide, yielded trapped phosphole oxides or phosphole oxide dimers, respectively, as new 7‐phosphanorbornene 7‐oxides. The stereostructures of three derivatives were evaluated by single crystal X‐ray analysis. The regio‐ and stereospecific dimerization was studied by B3LYP/6‐31G(d,p) quantum chemical calculations, whose results were in accord with syntheses. Novel mechanistic features were explored. The geometrical data obtained by single crystal X‐ray analysis validated the results of quantum chemical calculations, as the deviation was less than 3%.     

Poly(hydroxyisobutyrate) by ring‐opening polymerizations of 5,5‐dimethyl‐1,3,2‐dioxithiolan‐4‐one‐2‐oxide

α‐Hydroxyisobutyric acid anhydrosulfate HiBAS (5,5‐dimethyl‐1,3,2‐dioxithiolan‐4‐one‐2‐oxide) was polymerized under various reaction conditions and the solid reaction products were characterized by ¹H NMR spectroscopy, MALDI‐TOF mass spectrometry (MT m.s.), fast atom bombardment mass spectrometry (FAB m.s.), viscosity, and SEC measurements. Thermal polymerizations at 100 °C mainly yielded cyclic oligo polyesters presumably resulting from a zwitterionic polymerization. Cycles were also detected when pyridine was used as catalyst at 20 °C. When triethylamine was used as catalyst traces of H₂O played the role of initiators. Benzyl alcohol initiated the polymerization of HiBAS at 100 °C and yielded a polyester terminated by one benzylester and one OH endgroup. The SEC measurements indicated that all samples possess relatively low molar masses with number–average molecular weights ≤ 10,000 Da (in contrast to the literature data). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6229–6237, 2008     

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     

Synthesis and Structure of O,O‐Diethyl N‐[(trans‐4‐Aryl‐5,5‐dimethyl‐2‐oxido‐2λ5‐1,3,2‐dioxaphosphorinan‐2‐yl)methyl]phosphoramidothioates

A study on the synthesis of the novel N‐(cyclic phosphonate)‐substituted phosphoramidothioates, i.e., O,O‐diethyl N‐[(trans‐4‐aryl‐5,5‐dimethyl‐2‐oxido‐2λ⁵‐1,3,2‐dioxaphosphorinan‐2‐yl)methyl]phosphoramidothioates 4a – l , from O,O‐diethyl phosphoramidothioate ( 1 ), a benzaldehyde or ketone 2 , and a 1,3,2‐dioxaphosphorinane 2‐oxide 3 was carried out (Scheme 1 and Table 1). Some of their stereoisomers were isolated, and their structure was established. The presence of acetyl chloride was essential for this reaction and accelerated the process of intramolecular dehydration of intermediate 5 forming the corresponding Schiff base 7 (Scheme 2).     

7‐Nitro‐1H‐indazole,an inhibitor of nitric oxide synthase

The crystal structure of 7‐nitro‐1H‐indazole, C₇H₅N₃O₂, an inhibitor of nitric oxide synthase, shows the existence of an intramolecular hydrogen bond between an O atom of the nitro group and the NH group of the indazole ring. The crystal packing consists of intermolecular hydrogen bonding and indazole?indazole interactions.