Synthesis of 4‐silaspiro[3.4]octa‐1,5‐diene derivatives: hybrid spiro compounds

Trialkynyl(vinyl)silanes CH₂?CH? Si(C?C? R)₃ (R = Bu, Ph, p‐tolyl) were prepared and treated with 9‐borabicyclo[3.3.1]nonane (9‐BBN). Consecutive 1,2‐hydroboration and intramolecular 1,1‐carboboration reactions (each requires different reaction conditions) were studied. 1,2‐Hydroboration of the Si? vinyl group takes place at ambient temperature (23°C in tetrahydrofuran), followed by intramolecular 1,1‐vinylboration to give 1‐silacyclopent‐2‐ene derivatives, bearing still two alkynyl functions at the silicon atom. Further treatment with a second equivalent of 9‐BBN affords 1‐alkenyl‐1‐(alkynyl)‐1‐silacyclopent‐2‐ene derivatives. These undergo intramolecular 1,1‐vinylboration to give 4‐silaspiro[3.4]octa‐1,5‐dienes bearing the boryl groups at 2 and 6 positions. Protodeborylation of all new compounds (intermediates and final products) using acetic acid in slight excess afforded corresponding silanes including spirosilanes. All compounds were characterized using multinuclear NMR spectroscopy (¹H, ¹¹B, ¹³C, ²⁹Si) in solution state. Solid‐state structures for one of the trialkynyl(vinyl)silanes (R = p‐tolyl) and one of the 1‐silacyclopent‐2‐ene derivatives (R = Ph) were confirmed using X‐ray diffraction. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrophilic Reactivities of 1,2‐Diaza‐1,3‐dienes

The kinetics of the reactions of 1,2‐diaza‐1,3‐dienes 1 with acceptor‐substituted carbanions 2 have been studied at 20 °C. The reactions follow a second‐order rate law, and can be described by the linear free energy relationship log k(20 °C)=s(N+E) [Eq. (1)]. With Equation (1) and the known nucleophile‐specific parameters N and s for the carbanions, the electrophilicity parameters E of the 1,2‐diaza‐1,3‐dienes 1 were determined. With E parameters in the range of ?13.3 to ?15.4, the electrophilic reactivities of 1 a–d are comparable to those of benzylidenemalononitriles, 2‐benzylideneindan‐1,3‐diones, and benzylidenebarbituric acids. The experimental second‐order rate constants for the reactions of 1 a – d with amines 3 and triarylphosphines 4 agreed with those calculated from E, N, and s, indicating the applicability of the linear free energy relationship [Eq. (1)] for predicting potential nucleophilic reaction partners of 1,2‐diaza‐1,3‐dienes 1 . Enamines 5 react up to 10² to 10³ times faster with compounds 1 than predicted by Equation (1), indicating a change of mechanism, which becomes obvious in the reactions of 1 with enol ethers.     

Synthesis,Characterization and Molecular Structure of a New Tetrameric Palladium(II) Complex Containing Schiff‐Bases Derived from AMTTO (AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one)

The reactions of AMTTO = 4‐amino‐6‐methyl‐1,2,4‐triazine‐thione‐5‐one (AMTTO, 1 ) with 2‐hydroxybenzaldehyde (salicylaldehyde) and 4‐hydroxybenzaldehyde in methanol under reflux conditions led to the corresponding Schiff‐bases ( H₂L1 and H₂L2 ). The reaction of H₂L1 with palladium acetate in ethanol and additional recrystallization from toluene gave the tetrameric complex [Pd(L)]₄·2C₇H₈ ( 2 ). All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for H₂L1 at ?80 °C: space group P2₁/c with a = 1285.4(1), b = 707.7(1), c = 1348.2(1) pm, β = 109.32(1)°, Z = 4, R₁ = 0.0328, H₂L2 at ?80 °C: space group P4₃2₁2 with a = 762.5(1), b = 762.5(1), c = 4038.9(2) pm, Z = 8, R₁ = 0.025 and for 2 at ?103 °C: space group C2/c with a = 2862.5(6), b = 2847.6(6), c = 1727.8(4) pm, β = 105.18(3)°, Z = 8, R₁ = 0.0704.     

Synthesis,Characterization, and Crystal Structure of the New Schiff‐Bases derived from 1,2,4‐Triazole and the Structure of [(PPh3)2Cu(AMTT)]NO3·EtOH (AMTT = 4‐Amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione)

The reactions of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, L1 ) with 2‐thiophen carbaldehyde, salicylaldehyde and 2‐nitrobenzaldehyde in methanol led to the corresponding Schiff‐bases ( L1a‐c ). The reaction of L1 with [(PPh₃)₂Cu]NO₃ in ethanol gave the ionic complex [(PPh₃)₂Cu(L1)]NO₃·EtOH ( 2 ) All compounds were characterized by infrared spectroscopy, elemental analyses as well as by X‐ray diffraction studies. Crystal data for L1a at 20 °C: space group P2₁/n with a = 439.6(2), b = 2074.0(9), c = 1112.8(4) pm, β = 93.51(3)°, Z = 4, R₁ = 0.0406, L1b at ?80 °C: space group P2₁/n with a = 1268.9(2), b = 739.3(1), c = 1272.5(1) pm, β = 117.97(1)°, Z = 4, R₁ = 0.0361, L1c at ?80 °C: space group P2₁/n with a = 847.8(1), b = 1502.9(2), c = 981.5(2) pm, β = 110.34(1)°, Z = 4, R₁ = 0.0376 and for 2 at ?80 °C: space group with a = 1247.8(1), b = 1270.3(1), c = 1387.5(1) pm, α = 84.32(1)°, β = 84.71(1)°, γ = 63.12(1)°, Z = 2, R₁ = 0.0539.     

Formation of 6,10‐Diphenyl‐Substituted Heptalene‐4,5‐dicarboxylates

It is shown that 4,8‐diphenylazulene ( 1 ) can be easily prepared from azulene by two consecutive phenylation reactions with PhLi, followed by dehydrogenation with chloranil. Similarly, a Me group can subsequently be introduced with MeLi at C(6) of 1 (Scheme 2). This methylation led not only to the expected main product, azulene 2 , but also to small amounts of product 3 , the structure of which has been determined by X‐ray crystal‐structure analysis (cf. Fig. 1). As expected, the latter product reacts with chloranil at 40° in Et₂O to give 2 in quantitative yields. Vilsmeier formylation of 1 and 2 led to the formation of the corresponding azulene‐1‐carbaldehydes 4 and 5 . Reduction of 4 and 5 with NaBH₄/BF₃ ? OEt₂ in diglyme/Et₂O 1 : 1 and BF₃ ? OEt₂, gave the 1‐methylazulenes 6 and 7 , respectively. In the same way was azulene 9 available from 6 via Vilsmeier formylation, followed by reduction of azulene‐1‐carbaldehyde 8 (Scheme 3). The thermal reactions of azulenes 1, 6 , and 7 with excess dimethyl acetylenedicarboxylate (ADM) in MeCN at 100° during 72 h afforded the corresponding heptalene‐4,5‐dicarboxylates 11, 12 , and 13 , respectively (Scheme 4). On the other hand, the highly substituted azulene 9 gave hardly any heptalene‐4,5‐dicarboxylate.     

Sequential Intramolecular Diels–Alder Reaction of 3‐Heteroaryl‐2‐propenylamides of Ethenetricarboxylate

The reaction of 1,1,2‐ethenetricarboxylic acid 1,1‐diethyl ester with E‐3‐(2‐furyl)‐2‐propenylamines under the amide condensation conditions (EDCI/HOBt/Et₃N) on heating at 80–110°C afforded cis‐fused tricyclic compounds, furo[2,3‐f]isoindoles as major product. On the other hand, the reaction with E‐3‐(3‐furyl)‐2‐propenylamines afforded trans‐fused tricyclic compounds predominantly. The formation of amide/[4 + 2] cycloaddition/hydrogen‐shift reactions proceed sequentially. The observed stereoselectivity of the fused rings has been investigated by the density functional theory calculations. The reaction of 1,1,2‐ethenetricarboxylic acid 1,1‐diethyl ester with 3‐(3‐pyridinyl)‐2‐propen‐1‐amine under the amide condensation conditions afforded HOBt‐incorporated 3,4‐trans‐pyrrolidine selectively. The chemoselectivity and stereoselectivity of the reactions with (3‐heteroaryl)‐2‐propen‐1‐amines depend on the nature of heteroarenes.     

Reactions of Diazomethanes with 5‐Benzylidene‐3‐phenylrhodanine – A Computational Study

It has been shown previously that the reaction of diazomethane with 5‐benzylidene‐3‐phenylrhodanine ( 1 ) in THF at ?20° occurs at the exocyclic C?C bond via cyclopropanation to give 3a and methylation to yield 4 , respectively, whereas the corresponding reaction with phenyldiazomethane in toluene at 0° leads to the cyclopropane derivative 3b exclusively. Surprisingly, under similar conditions, no reaction was observed between 1 and diphenyldiazomethane, but the 2‐diphenylmethylidene derivative 5 was formed in boiling toluene. In the present study, these results have been rationalized by calculations at the DFT B3LYP/6‐31G(d) level using PCM solvent model. In the case of diazomethane, the formation of 3a occurs via initial Michael addition, whereas 4 is formed via [3+2] cycloaddition followed by N₂ elimination and H‐migration. The preferred pathway of the reaction of 1 with phenyldiazomethane is a [3+2] cycloaddition, subsequent N₂ elimination and ring closure of an intermediate zwitterion to give 3b . Finally, the calculations show that the energetically most favorable reaction of 1 with diphenyldiazomethane is the initial formation of diphenylcarbene, which adds to the S‐atom to give a thiocarbonyl ylide, followed by 1,3‐dipolar electrocyclization and S‐elimination.     

Coupling of two diazotized 3‐aminothieno[3,4‐c]coumarins with aromatic amines

The coupling reactions of two diazotized 3‐aminothieno[3,4‐c]coumarins were investigated. Compounds 1a , 1b both react with sodium nitrite in concentrated sulphuric acid at 0–5°C to give the diazotized intermediates 2 and 3 , the latter resulting from the acid ‐catalyzed hydrolysis of the lactonic ring of 2 . The in situ formed diazonium salts react with aromatic amines ( 4 ) to afford a series of arylazothiophenes dyes in the form of their ammonium sulfate salts. With diazotized aniline, besides the normally expected phenylazothiophene 10 from the reaction with compound 1a , the corresponding product of acid hydrolysis 11 was also isolated. In at least one of the cases, the thienyl diazonium salt 2 undergoes a Gomberg–Bachmann arylation reaction with p‐nitroaniline to give the 2‐arylthiophene 9 . The direct hydrolysis of compounds 1a , 1b by concentrated sulphuric acid and subsequent oxidative dimerization of the primary product of acid hydrolysis led to compound 12 . J. Heterocyclic Chem., (2011).     

Nickel‐Catalyzed Mizoroki–Heck‐ versus Michael‐Type Addition of Organoboronic Acids to α,β‐Unsaturated Alkenes through Fine‐Tuning of Ligands

Various arylboronic acids reacted with activated alkenes in the presence of [Ni(dppe)Br₂], ZnCl₂, and H₂O in CH₃CN at 80 °C to give the corresponding Mizoroki–Heck‐type addition products in good to excellent yields. Furthermore, 1 equivalent of the hydrogenation product of the activated alkene was also produced. By tuning the ligands of the nickel complexes and the reaction conditions, Michael‐type addition was achieved in a very selective manner. Thus, various p‐ and o‐substituted arylboronic acids or alkenylboronic acid reacted smoothly with activated alkenes in CH₃CN at 80 °C for 12 h catalyzed by Ni(acac)₂, P(o‐anisyl)₃, and K₂CO₃ to give the corresponding Michael‐type addition products in excellent yields. However, for m‐substituted arylboronic acids, the yields of Michael‐type addition products are very low. The cause of this unusual meta‐substitution effect is not clear. By altering the solvent or phosphine ligand, the product yields for m‐substituted arylboronic acids were greatly improved. In contrast to previous results in the literature, the present catalytic reactions required water for Mizoroki–Heck‐type products and dry reaction conditions for Michael‐type addition products. Possible mechanistic pathways for both addition reactions are proposed.     

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.     

Synthesis and antimicrobial activity of novel 2‐alkyl/arylcarbamato‐6‐(1,1‐dimethylethyl)‐3‐cyclohexyl‐3,4‐dihydro‐2H‐1,3,2‐benzoxazaphosphorine‐2‐oxides

Novel 2‐alkyl/arylcarbamato‐6‐(1,1‐dimethylethyl)‐3‐cyclohexyl‐3,4‐dihydro‐2H‐1,3,2‐benzoxaza‐phosphorine‐2‐oxides ( IV ) have been synthesized from reactions of 2‐cyclohexylaminomethyl‐4‐t‐butylphenol I [8c] with various dichlorophosphinyl carbamates ( III ) [8a‐b] in dry toluene in the presence of triethylamine at 40‐50 °C. All the title compounds ( IVa‐j ) at reflux temperature are degraded to 2‐amino‐6‐(1,1‐dimethylethyl)‐3‐cyclohexyl‐3,4‐dihydro‐2H‐1,3,2‐benzoxazaphosphorine‐2‐oxide ( IVk ) exclusively. The structures are determined by ir, nmr and mass spectral studies. They were screened for antifungal activity against Penicillium notatum, Aspergillus niger and Helminthosporium sps, and antibacterial activity on Escherchia coli, Staphylococcus aureus and Pseudomonas aeruginosa. A few of them possess significant activity.     

2‐(4‐Bromophenyl)‐1,2‐dihydropyrimido[1,2‐a]benzimidazol‐4(3H)‐one and 4‐(4‐methylphenyl)‐3,4‐dihydropyrimido[1,2‐a]benzimidazol‐2(1H)‐one form hydrogen‐bonded base‐paired dimers

The title compounds, 2‐(4‐bromo­phenyl)‐1,2‐di­hydro­pyrimido­[1,2‐a]­benzimidazol‐4‐(3H)‐one, C₁₆H₁₂Br­N₃O, (IVa), and 4‐(4‐methylphenyl)‐3,4‐dihydropyrimido[1,2‐a]benzimidazol‐2‐(1H)‐one, C₁₇H₁₅N₃O, (Vb), both form R(8) centrosymmetric dimers via N—H?N hydrogen bonds. The N?N distance is 2.943 (3) Å for (IVa) and 2.8481 (16) Å for (Vb), with the corresponding N—H?N angles being 129 and 167°, respectively. However, in other respects, the supra­molecular structures of the two compounds differ. Both compounds contain different C—H?π interactions, in which the C—H?π(centroid) distances are 2.59 and 2.47 Å for (IVa) and (Vb), respectively (the latter being a short distance), with C—H?π(centroid) angles of 158 and 159°, respectively. The supramolecular structures also differ, with a short Br?O distance of 3.117 (2) Å in bromo derivative (IVa), and a C—H?O interaction with a C?O distance of 3.2561 (19) Å and a C—H?O angle of 127° in tolyl system (Vb). The di­hydro­pyrimido part of (Vb) is disordered, with a ratio of the major and minor components of 0.9:0.1. The disorder consists of two non‐interchangeable envelope conformers, each with an equatorial tolyl group and an axial methine H atom.     

Diastereo‐ and Enantioselective Intramolecular [2+2] Photocycloaddition Reactions of 3‐(ω′‐Alkenyl)‐ and 3‐(ω′‐Alkenyloxy)‐Substituted 5,6‐Dihydro‐1H‐pyridin‐2‐ones

3‐(ω′‐Alkenyl)‐substituted 5,6‐dihydro‐1H‐pyridin‐2‐ones 2 – 4 were prepared as photocycloaddition precursors either by cross‐coupling from 3‐iodo‐5,6‐dihydro‐1H‐pyridin‐2‐one ( 8 ) or—more favorably—from the corresponding α‐(ω′‐alkenyl)‐substituted δ‐valerolactams 9 – 11 by a selenylation/elimination sequence (56–62 % overall yield). 3‐(ω′‐Alkenyloxy)‐substituted 5,6‐dihydro‐1H‐pyridin‐2‐ones 5 and 6 were accessible in 43 and 37 % overall yield from 3‐diazopiperidin‐2‐one ( 15 ) by an α,α‐chloroselenylation reaction at the 3‐position followed by nucleophilic displacement of a chloride ion with an ω‐alkenolate and oxidative elimination of selenoxide. Upon irradiation at λ=254 nm, the precursor compounds underwent a clean intramolecular [2+2] photocycloaddition reaction. Substrates 2 and 5 , tethered by a two‐atom chain, exclusively delivered the respective crossed products 19 and 20 , and substrates 3 , 5 , and 6 , tethered by longer chains, gave the straight products 21 – 23 . The completely regio‐ and diastereoselective photocycloaddition reactions proceeded in 63–83 % yield. Irradiation in the presence of the chiral templates (?)‐ 1 and (+)‐ 31 at ?75 °C in toluene rendered the reactions enantioselective with selectivities varying between 40 and 85 % ee. Truncated template rac‐ 31 was prepared as a noranalogue of the well‐established template 1 in eight steps and 56 % yield from the Kemp triacid ( 24 ). Subsequent resolution delivered the enantiomerically pure templates (?)‐ 31 and (+)‐ 31 . The outcome of the reactions is compared to the results achieved with 4‐substituted 5,6‐dihydro‐1H‐pyridin‐2‐ones and quinolones.     

Synthesis of 3‐(ω‐Hydroxyalkoxy)isobenzofuran‐1(3H)‐ones by Trifluoroacetic Acid‐Mediated Lactonization of tert‐Butyl 2‐(1,3‐Dioxol‐2‐yl)‐ or 2‐(1,3‐Dioxan‐2‐yl)benzoates

An efficient two‐step method for the preparation of 3‐(2‐hydroxyethoxy)‐ or 3‐(3‐hydroxypropoxy)isobenzofuran‐1(3H)‐ones 3 has been developed. Thus, the reaction of 1‐(1,3‐dioxol‐2‐yl)‐ or 1‐(1,3‐dioxan‐2‐yl)‐2‐lithiobenzenes, generated in situ by the treatment of 1‐bromo‐2‐(1,3‐dioxol‐2‐yl)‐ or 1‐bromo‐2‐(1,3‐dioxan‐2‐yl)benzenes 1 with BuLi in THF at ?78°, with (Boc)₂O afforded tert‐butyl 2‐(1,3‐dioxol‐2‐yl)‐ or 2‐(1,3‐dioxan‐2‐yl)benzoates 2 , which can subsequently undergo facile lactonization on treatment with CF₃COOH (TFA) in CH₂Cl₂ at 0° to give the desired products in reasonable yields.     

Design,Synthesis, and Herbicidal Activities of 3‐Aryl‐4‐substituted‐5‐[3‐(trifluoromethyl)phenoxy]‐1,2,4‐triazoles

In order to find novel bleaching herbicide lead compounds, a series of novel 3‐aryl‐4‐substituted‐5‐[3‐(trifluoromethyl)phenoxy]‐1,2,4‐triazoles were designed and synthesized by the multi‐step reactions. N‐(Arylformamido)phenylthioureas undergo ring closure in the presence of sodium hydroxide to generate 3‐aryl‐4‐substituted‐4H‐[1,2,4]triazol‐5‐thiols 1 , which reacted with methyl sulfate in the presence of K₂CO₃ to give 3‐aryl‐5‐methylsulfanyl‐4‐substituted‐4H‐[1,2,4]triazoles 2 . The target compounds 4 were synthesized by the oxidation of 2 in the presence of H₂O₂ and Na₂WO₄, followed by the substitution with 3‐(trifluoromethyl)phenol in moderate to good yields. Their structures were confirmed by IR, ¹H NMR, EI–MS, and elemental analyses. The preliminary bioassay indicated that some of them displayed moderate to good selective herbicidal activity against Brassica campestris L at the concentration of 100 µg/mL. Compounds 4c and 4i possessed 75.0% and 82.6% inhibition against Brassica campestris L at the concentration of 100 µg/mL. However, the target compounds 4 showed weak herbicidal activity against Echinochloa crus‐galli at the concentration of 100 and 10 µg/mL.     

One‐Pot Synthesis of 3‐Substituted 3,4‐Dihydro‐1,2,3‐benzotriazine Derivatives Based on the Reaction of o‐Bromobenzyl Azides with Butyllithium

An efficient one‐pot procedure for the preparation of 3‐substituted 3,4‐dihydro‐1,2,3‐benzotriazines 2, 3 , and 4 from o‐bromobenzyl azides 1 is described. The reaction of these azides with BuLi in THF at ?78° generates o‐lithiobenzyl azides via the Br/Li exchange. These lithium compounds immediately undergo intramolecular cyclization to give the corresponding (dihydro‐1,2,3‐benzotriazinyl)lithium intermediates, which are trapped with a variety of acylating agents or BnBr at N(3) exclusively to provide the desired products in moderate to good yields.     

Isomeric 3‐ and 4‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline

The title isomers, namely 3‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline, (I), and 4‐chloro‐N‐[1‐(1H‐pyrrol‐2‐yl)ethylidene]aniline, (II), both C₁₂H₁₁ClN₂, differ in the position of the chlorine substitution. Both compounds have the basic iminopyrrole structure, which shows a planar backbone with similar features. The dihedral angle formed by the planes of the pyrrole and benzene rings is 75.65 (7)° for (I) and 86.56 (8)° for (II). The H atom bound to the pyrrole N atom is positionally disordered and partial protonation occurs at the imino N atom in (I), while this phenomenon is absent from the structure of (II). Packing interactions for both compounds include intermolecular N—H...N hydrogen bonds and C—H...π interactions, forming centrosymmetric dimers for both (I) and (II).     

7‐Iodo‐8‐aza‐7‐deaza‐2′‐deoxy­adenosine and 7‐bromo‐8‐aza‐7‐deaza‐2′‐deoxyadenosine

The isomorphous structures of the title molecules, 4‐amino‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐3‐iodo‐1H‐pyrazolo‐[3,4‐d]pyrimidine, (I), C₁₀H₁₂IN₅O₃, and 4‐amino‐3‐bromo‐1‐(2‐deoxy‐β‐d ‐erythro‐pento­furan­osyl)‐1H‐pyrazolo[3,4‐d]­pyrimidine, (II), C₁₀H₁₂BrN₅O₃, have been determined. The sugar puckering of both compounds is C1′‐endo (^1′E). The N‐­glycosidic bond torsion angle χ¹ is in the high‐anti range [?73.2 (4)° for (I) and ?74.1 (4)° for (II)] and the crystal structure is stabilized by hydrogen bonds.     

Synthesis and bioactivity of 6‐bromo‐2‐(substituted)‐3‐(1‐phenyl‐ethyl)‐ 3,4‐dihydro‐1H‐ isophosphinoline 2‐chalcogenides

Synthesis of 6‐bromo‐2‐(substituted)‐3‐(1‐phenyl‐ethyl)‐3,4‐dihydro‐1H‐isophosphinoline 2‐chalco‐genides derivatives (6) were synthesized from 2‐[(1‐phenylethylamino)methyl]‐4‐bromophenol ( 1 ) by reaction with aryl/alkyl phosphoro dichloridates ( 2 ) in the presence of triethylamine at 55°C to 60°C to obtained the title compounds ( 6a‐g ). The title compounds ( 6h‐j ), were prepared via intermediate route. Few other title compounds ( 8a‐c ) were accomplished through a two step synthetic route involving 1 with dichlorophenyl phosphine ( 2a ) and dichloroethyl phosphine ( 2a,b ) in the presence of triethylamine in dry toluene under N₂ atmosphere to form the corresponding trivalent phosphorus intermediate (7) . In the second step they were further converted to the corresponding chalcogenides 8a‐c by reaction with hydrogen peroxide, sulfur and selenium respectively. They exhibited significant antibacterial, fungal and insecticidal activity.     

7‐Deaza‐2′‐deoxy­guanosine

In the title compound, 2‐amino‐7‐(2‐deoxy‐β‐d ‐erythro‐pentofuran­osyl)‐3,7‐dihydro­pyrrolo[2,3‐d]pyrimidin‐4‐one, C₁₁H₁₄N₄O₄, the N‐glycosylic bond torsion angle, χ, is anti [−106.5 (3)°]. The 2′‐deoxy­ribofuran­osyl moiety adopts the ³T₄ (N‐type) conformation, with P = 39.1° and τ_m = 40.3°. The conformation around the exocyclic C—C bond is ap (trans), with a torsion angle, γ, of −173.8 (3)°. The nucleoside forms a hydrogen‐bonded network, leading to a close‐packed multiple‐layer structure with a head‐to‐head arrangement of the bases. The nucleobase interplanar O=C—C⋯NH₂ distance is 3.441 (1) Å.