Anionic polymerization of methyl methacrylate by initiating systems based on lithium amides of various secondary amines

The anionic polymerization of methyl methacrylate in toluene at −78 °C with lithium amides of various secondary amines (diisopropylamine, N‐isopropylaniline, N‐n‐butylaniline, indoline, and N‐ethyl‐o‐toluidine) as initiators was studied. The tacticity of the resulting poly(methyl methacrylate)s (PMMAs) was dependent on the kind of secondary amine, and highly isotactic PMMAs (91–93% mm) were obtained when lithium amides of N‐isopropylaniline and N‐n‐butylaniline were employed. The isotacticity of the PMMAs further increased up to 98% mm with initiating systems composed of the lithium amides, n‐butyllithium, and transition‐metal halides (WCl₆, MoCl₅, and NbCl₅). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4405–4411, 2005     

Two New Insecticidal Amide Dimers from Fruits of Piper nigrum Linn.

The methanolic extract of dried ground seeds of Piper nigrum Linn . afforded fourteen compounds, of which thirteen were amides, including two new isomeric insecticidal amides, pipsaeedine ( 1 ) and pipbinine ( 2 ), along with eleven known amides and piptaline; (this is the first report of isolation of these compounds from this plant). The structures of 1 and 2 have been elucidated as (E,E)‐1‐[(E)‐5‐(7‐{6‐[5‐(piperidin‐1‐yl)‐5‐oxopent‐3‐enyl]‐1,3‐benzodioxol‐4‐yl}‐1,3‐benzodioxol‐5‐yl)‐1‐oxopenta‐2,4‐dienyl]piperidine and (E,E)‐1‐[(E)‐5‐(4‐{6‐[5(piperidin‐1‐yl)‐5‐oxopent‐3‐enyl]‐1,3‐benzodioxol‐4‐yl}‐1,3‐benzodioxol‐5‐yl)‐1‐oxopenta‐2,4‐dienyl]piperidine, respectively, through extensive 1D‐ and 2D‐NMR spectral studies, while the known constituents have been identified through comparison of their spectral data with those reported in the literature. Compounds 1 and 2 exhibited toxicities of 45.0 and 40.0 ppm, respectively, against fourth instar larvae of Aedes aegypti Liston.     

Synthesis and evaluation of polyacrylamides derived from polycyclic pendant naphthalene,indole, and phenothiazine based chalcone moiety as potent antimicrobial agents

Polycyclic chalcone‐containing polyacrylamides, namely, poly ((N‐(4‐((E)‐3‐(naphthalen‐6‐yl)‐3‐oxoprop‐1‐enyl) phenyl) acrylamide), poly((N‐(4‐((E)‐3‐(1H‐indol‐3‐yl)‐3‐oxoprop‐1‐enyl) phenyl) acrylamide), and poly((N‐(4‐((E)‐3‐oxo‐3‐(10H‐phenothiazin‐8‐yl) prop‐1‐enyl) phenyl) acrylamide), were synthesized by Claisen–Schmidt condensation reaction, followed by ultrasonic irradiation reduction. The synthesized polymers were characterized by Fourier transform infrared spectroscopy, ¹H nuclear magnetic resonance, and ¹³C nuclear magnetic resonance spectroscopic technique. The newly synthesized polymers have been screened for antibacterial and antifungal activities by using resazurin reduction assay method, and the resulting polyacrylamides showed promising activity against various tested bacteria and fungi. Among the polymers, poly((N‐(4‐((E)‐3‐oxo‐3‐(10H‐phenothiazin‐8‐yl) prop‐1‐enyl) phenyl) acrylamide) and poly((N‐(4‐((E)‐3‐(1H‐indol‐3‐yl)‐3‐oxoprop‐1‐enyl) phenyl) acrylamide) exhibited better antifungal and antibacterial activities than poly ((N‐(4‐((E)‐3‐(naphthalen‐6‐yl)‐3‐oxoprop‐1‐enyl) phenyl) acrylamide), whereas all the polymers do not show any sign of antibacterial and antifungal activity against Streptococcus faecalis and Candida glabrata. Copyright © 2016 John Wiley & Sons, Ltd.     

New Long‐Chain Esters and Adenine Analogs from the Leaves of Formosan Bridelia balansae

Six new compounds, including the two long‐chain esters balansenate I (=6,8,11‐trimethyldodecanoic acid (2E)‐3‐methylhexadec‐2‐enyl ester; 1 ) and balansenate II (=10,12,15‐trimethylhexadedecanoic acid (2E)‐3‐methylhexadec‐2‐enyl ester; 2 ), the eburicane‐like triterpenoid bridelone (=hexadecahydro‐4,4,10,13,14‐pentamethyl‐17‐(5‐methyl‐1,4‐dimethylenehexyl)‐3H‐cyclopenta[a]phenanthren‐3‐one; 3 ), the ‘deimino‐xanthine', bridelonine (=5‐(3‐methylbut‐2‐enyl)pyrrolo[3,4‐d]imidazole‐4,6(1H,5H)‐dione; 6 ), and the two adenine analogs 9‐(3‐methylbut‐2‐enyl)adenine ( 7 ) and 1‐(3‐methylbut‐2‐enyl)adenine ( 8 ), besides three known compounds, i.e., N⁶‐(3‐methylbut‐2‐enyl)adenine ( 4 ), 3‐(3‐methylbut‐2‐enyl)adenine ( 5 ), and adenine ( 9 ), were isolated from the leaves of Formosan Bridelia balansae. The novel skeleton of 6 consists of a fused pyrrolidine‐2,5‐dione and imidazole moiety. The already known adenines 7 and 8 were isolated for the first time from a plant. The structures of the isolated compounds were elucidated by spectroscopic analyses.     

Hydrogen‐bond motifs in N‐monosubstituted derivatives of barbituric acid: 5‐allyl‐5‐isopropyl‐1‐methylbarbituric acid (enallylpropymal) and 1,5‐di(but‐2‐enyl)‐5‐ethylbarbituric acid

Both title structures exhibit essentially planar barbiturate rings. The crystal structure of enallylpropymal (5‐allyl‐5‐isopropyl‐1‐methylbarbituric acid), C₁₁H₁₆N₂O₃, is composed of centrosymmetric N—H...O hydrogen‐bonded dimers, while 1,5‐di(but‐2‐enyl)‐5‐ethylbarbituric acid, C₁₄H₂₀N₂O₃, forms N—H...O hydrogen‐bonded helical chains. Each of the ten known crystal structures of closely related N‐monosubstituted derivatives of barbituric acid displays one of the fundamental N—H...O hydrogen‐bonded motifs of the two title structures, i.e. either a dimer or a chain.     

Copolymerizations of propylene with functionalized long‐chain α‐olefins using group 4 organometallic catalysts and their membrane application

Introduction of functional groups into polyolefins has the potential of broadening their end use. An attractive method for preparing polyolefins containing functional groups is the copolymerization of the olefins with α‐olefins containing a functional group. Copolymerizations of propylene with 10‐undecen‐1‐ol, containing a hydroxyl group protected by either TIBA or TBDMSCl, 11‐chloro‐1‐undecene, 5‐bromopent‐1‐ene and N‐allyl‐2,2,2‐trifluoroacetamide were performed using three organometallic catalysts: the metallocene rac‐Et(Ind)₂ZrCl₂ and two new benzamidinate catalysts [3‐C₅H₄NC(NSiCH₃)₂]₂TiCl₂ and [(m‐OMe‐C₆H₄NC(NSiCH₃)₂]₂ZrCl₂. 10‐Undecene‐1‐ol protected “in situ” with TIBA and N‐(dec‐9‐enyl)‐2,2,2‐trifluoroacetamide gave copolymers with similar polar monomer incorporation percentages and molecular weights 17%; 28,900 g/mol for the protected 10‐undecene‐1‐ol, and 15%; 27,100 g/mol for N‐(dec‐9‐enyl)‐2,2,2‐trifluoroacetamide. 11‐Chloro‐1‐undecene gave copolymers with up to 22% incorporation for 0.12 M of the comonomer in the reaction feed. The obtained copolymers were characterized by NMR, DSC, and GPC. Membranes were prepared from two copolymers containing the hydroxyl groups (6 and 10%) and one copolymer containing chlorine groups (7%). The membranes prepared could be wetted in contrast to polypropylene membranes which do not contain functional groups. In addition, it was observed that for both type of membranes prepared from the different copolymers containing the hydroxyl groups, the flux was significantly greater than for the membrane prepared from the copolymer containing a chlorine groups. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis of 1‐Acyl‐3,4‐dihydroquinazoline‐2(1H)‐thiones by Cyclization of N‐[2‐(Isothiocyanatomethyl)phenyl] Amides Generated in situ from N‐[2‐(Azidomethyl)phenyl] Amides

An efficient method for the preparation of 1‐acyl‐3,4‐dihydroquinazoline‐2(1H)‐thiones 5 has been developed. The reaction of N‐[2‐(azidomethyl)phenyl] amides 3 , easily prepared by a three‐step sequence starting with (2‐aminophenyl)methanols, with Ph₃P, followed by CS₂, allowed generation of N‐[2‐(isothiocyanatomethyl)phenyl]‐amide intermediates 4 , which underwent cyclization on treatment with NaH to furnish the corresponding desired products in generally good yields.     

Cyclisation versus 1,1‐Carboboration: Reactions of B(C6F5)3 with Propargyl Amides

A series of propargyl amides were prepared and their reactions with the Lewis acidic compound B(C₆F₅)₃ were investigated. These reactions were shown to afford novel heterocycles under mild conditions. The reaction of a variety of N‐substituted propargyl amides with B(C₆F₅)₃ led to an intramolecular oxo‐boration cyclisation reaction, which afforded the 5‐alkylidene‐4,5‐dihydrooxazolium borate species. Secondary propargyl amides gave oxazoles in B(C₆F₅)₃ mediated (catalytic) cyclisation reactions. In the special case of disubstitution adjacent to the nitrogen atom, 1,1‐carboboration is favoured as a result of the increased steric hindrance (1,3‐allylic strain) in the 5‐alkylidene‐4,5‐dihydrooxazolium borate species.     

Copper‐Catalyzed Reductive N‐Alkylation of Amides with N‐Tosylhydrazones Derived from Ketones

A CuI‐catalyzed reductive coupling of ketone‐derived N‐tosylhydrazones with amides is presented. Under the optimized conditions, an array of N‐tosylhydrazones derived from aryl–alkyl and diaryl ketones could couple effectively with a wide variety of (hetero)aryl as well as aliphatic amides to afford the N‐alkylated amides in high yields. The method represents the very few examples for reliably accessing secondary and tertiary amides through a reductive N‐alkylation protocol.     

Diels–Alder Additions,Ene Reactions,and Condensations of 4‐(Acylamino)‐5‐nitrosopyrimidines – Synthesis of 8‐Substituted Guanines and of 6‐Substituted Pteridinones

4‐(Acylamino)‐5‐nitrosopyrimidines react either by a reductive condensation to provide 8‐substituted guanines, or by a Diels–Alder cycloaddition, or an ene reaction, to provide 6‐substituted pteridinones, depending on the nature of the acyl group and the reaction conditions. Experimental details are provided for the transformation of (acylamino)‐nitrosopyrimidines to 8‐substituted guanines, and the scope of the reaction is further demonstrated by transforming the trifluoro acetamide 25 to the 8‐(trifluoromethyl)guanine ( 27 ), and the N,N′‐bis(nitrosopyrimidinyl)‐dicarboxamide 29 to the (R,R)‐1,2‐di(guan‐8‐yl)ethane‐1,2‐diol ( 32 ). An intramolecular Diels–Alder reaction of the N‐sorbyl (=N‐hexa‐2,4‐dienoyl) nitrosopyrimidine 10 , followed by a spontaneous elimination to cleave the N,O bond of the initial cycloaddition product provided the pteridinones 14 or 15 , characterized by a (Z)‐ or (E)‐3‐hydroxyprop‐1‐enyl group at C(6). Treatment of 10 with Ph₃P led to the C(8)‐penta‐1,3‐dienyl‐guanine 18 . The ene reaction of the N‐crotonyl (=N‐but‐2‐enoyl) nitrosopyrimidine 19 provided the 6‐vinyl‐pteridinone 20a that dimerized readily to 21a , while treatment of 19 with Ph₃P led in high yield to 8‐(prop‐1‐enyl)guanine ( 23 ). The structure of the dimer 21 was established by X‐ray analysis of its bis(N,N‐dimethylformamidine) derivative 21b . The crystal structure of the nitroso amide 10 is characterized by two molecules in the centrosymmetric unit cell. Intermolecular H‐bonds connect the amino group to the amide carbonyl and to N(1). The crystalline bis(purine) 30 forms a left‐handed helix with four molecules per turn and a pitch of 30.2 Å.     

7,7‐Dimethyl‐5H‐di­benzo[e,i][1,4,8]triaza­cyclo­undecine‐6,9,15(7H,8H,14H)‐trione pyridine solvate

The X‐ray crystal structure and hydrogen‐bonding patterns of the title compound, C₁₈H₁₇N₃O₃·C₅H₅N, a non‐N‐alkyl­ated cyclotripeptide containing one α‐ and two β‐amino acids, are reported. The amides in the 11‐membered ring have an unprecedented all‐transoid configuration. The torsion angles and Dunitz parameters describing non‐planarity of the amides contained in the cyclotripeptide are discussed.     

Silver‐Mediated N‐Trifluoromethylation of Amides and Peptides

We report herein the direct N‐trifluoromethylation of N‐H amides. Promoted by AgOTf and 2‐fluoropyridine, the reaction of a variety of amides with Selectfluor, TMSCF₃ and CsF proceeds smoothly at room temperature leading to the corresponding N‐trifluoromethylated products in satisfactory yields. The protocol is also applicable to amino acid derivatives, resulting in efficient and chemoselective N‐trifluoromethylation of di‐ and tri‐peptides with retention of configuration. A mechanism involving reductive elimination of Ag(III) intermediates to form N—CF₃ bonds is proposed.     

Ten‐vertex rhodadithiaborane ­chemistry: [8‐{I(CH2)5}‐3‐(η5‐C5Me5)‐arachno‐3,7,8‐RhS2B8H9]

Neutral 8‐(5‐iodo‐n‐pentyl)‐3‐(η⁵‐penta­methyl­cyclo­pentadi­enyl)‐arachno‐3‐rhoda‐7,8‐di­thia­undecaborane, [Rh(C₅H₁₉B₈­IS₂)­(C₁₀H₁₅)], obtained from the [arachno‐7,8‐S₂B₉H₁₀]^? anion by treatment with I(CH₂)₅I followed by [Rh(C₅Me₅)Cl₂]₂ and N,N,N′,N′‐tetra­methyl‐1,8‐di­amino­naphthalene, has the 11‐vertex cluster geometry of [arachno‐7,8‐S₂B₉H₁₀]^?, but with an {Rh(C₅Me₅)} unit in the 3‐position instead of a {BH} unit, and with a –(CH₂)₅I chain attached exo to an S atom.     

Synthesis of 4‐Aryl‐1,7‐naphthyridine‐2(1H)‐thiones by the Electrocyclic Reaction of 4‐(1‐Arylalk‐1‐enyl)‐3‐isothiocyanatopyridines Generated in situ from the Corresponding Isocyanides

A convenient synthis for 4‐substituted and 3,4‐disubstituted 1,7‐naphthyridine‐2(1H)‐thiones 7 has been developed. The method is based on the electrocyclic reaction of 4‐(1‐arylalk‐1‐enyl)‐3‐isothiocyanatopyridines 6 , generated in situ by the treatment of the respective isocyanides 5 with S₈ in the presence of a catalytic amount of selenium. The isocyanides 5 can be easily prepared from commercially available pyridin‐3‐amine by conventional organic reactions.     

Synthesis and Screening of New Chiral Ligands for the Copper‐Catalysed Enantioselective Allylic Substitution

The synthesis of the new chiral ligands 6ae, 8ae, 9ae , and 11ae starting from the chiral β‐[(Boc)amino]sulfonamide 3ae is reported. The β‐amino group of 3ae was deprotected and condensed with 3,5‐dichlorosalicylaldehyde ( 4 ) to yield the known Schiff base 5ae , which was then reduced to the amino compound 6ae (Scheme 3). Alternatively, condensation of the free amino compound with 2‐(diphenylphosphanyl)benzaldehyde ( 7 ) afforded the imino ligand 8ae which upon reduction yielded the amino ligand 9ae (Scheme 4). The free amino compound derived from 3ae was also coupled with 2‐(diphenylphosphanyl)benzoic acid ( 10 ) to give ligand 11ae (Scheme 5). These ligands were tested in the copper‐catalysed allylic substitution reaction of cinnamyl (=3‐phenylprop‐2‐enyl) phosphate 12 with diethylzinc as a nucleophile. Ligands 5ae, 6ae, 8ae , and 11ae gave excellent ratios (100 : 0) of the S_N2′/S_N2 products (Scheme 6 and Table 1). Ligand 11ce , identified from the screening of a small library of ligands of general formula 11 , promoted the allylic substitution reaction with moderate enantioselectivity (40% for the S_N2′ product 13 (Scheme 8 and Table 3)).     

Enantio‐ and Site‐Selective α‐Fluorination of N‐Acyl 3,5‐Dimethylpyrazoles Catalyzed by Chiral π–CuII Complexes

Catalytic enantioselective α‐fluorination reactions of carbonyl compounds are among the most powerful and efficient synthetic methods for constructing optically active α‐fluorinated carbonyl compounds. Nevertheless, α‐fluorination of α‐nonbranched carboxylic acid derivatives is still a big challenge because of relatively high pK_a values of their α‐hydrogen atoms and difficulty of subsequent synthetic transformation without epimerization. Herein we show that chiral copper(II) complexes of 3‐(2‐naphthyl)‐l ‐alanine‐derived amides are highly effective catalysts for the enantio‐ and site‐selective α‐fluorination of N‐(α‐arylacetyl) and N‐(α‐alkylacetyl) 3,5‐dimethylpyrazoles. The substrate scope of the transformation is very broad (25 examples including a quaternary α‐fluorinated α‐amino acid derivative). α‐Fluorinated products were converted into the corresponding esters, secondary amides, tertiary amides, ketones, and alcohols with almost no epimerization in high yield.     

A New Synthesis of Pteridines

A new synthesis of pteridines possessing a (substituted) (Z)‐3‐hydroxyprop‐1‐enyl group at C(6) is based on the acylation of 4‐amino‐5‐nitrosopyrimidines with dienoic acid chlorides, followed by a high‐yielding intramolecular hetero‐Diels–Alder cycloaddition and cleavage of the N? O bond leading to 4 . Thermolysis of the resulting pteridines 4 possessing a benzyloxy group at C(4) led to the products 5 , resulting from isomerisation of the 3‐hydroxyprop‐1‐enyl to an 3‐oxopropyl side chain, while the analogous pteridine 8 possessing an NH₂ group at C(4) remained unaffected.     

Perchloric Acid–Silica (HClO4⋅SiO2)‐Catalyzed Synthesis of 14‐Alkyl‐ or 14‐Aryl‐14H‐dibenzo[a,j]xanthenes and N‐[(2‐Hydroxynaphthalen‐1‐yl)methyl]amides

The synthesis of 14‐aryl‐ or 14‐alkyl‐14H‐dibenzo[a,j]xanthenes 3 involving the treatment of naphthalen‐2‐ol ( 1 ) with arenecarboxaldehydes or alkanals 2 in the presence of HClO₄?SiO₂ as a heterogeneous catalyst was achieved (Table 1), and this reaction was extended to the preparation of N‐[(2‐hydroxynaphthalen‐1‐yl)methyl]amides 5 by a three‐component reaction with urea ( 4a ) or an amide 4b – d as a third reactant (Table 2).     

Structural Diversity in Alkali Metal and Alkali Metal Magnesiate Chemistry of the Bulky 2,6‐Diisopropyl‐N‐(trimethylsilyl)anilino Ligand

Bulky amido ligands are precious in s‐block chemistry, since they can implant complementary strong basic and weak nucleophilic properties within compounds. Recent work has shown the pivotal importance of the base structure with enhancement of basicity and extraordinary regioselectivities possible for cyclic alkali metal magnesiates containing mixed n‐butyl/amido ligand sets. This work advances alkali metal and alkali metal magnesiate chemistry of the bulky arylsilyl amido ligand [N(SiMe₃)(Dipp)]^? (Dipp=2,6‐iPr₂‐C₆H₃). Infinite chain structures of the parent sodium and potassium amides are disclosed, adding to the few known crystallographically characterised unsolvated s‐block metal amides. Solvation by N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine (PMDETA) or N,N,N′,N′‐tetramethylethylenediamine (TMEDA) gives molecular variants of the lithium and sodium amides; whereas for potassium, PMDETA gives a molecular structure, TMEDA affords a novel, hemi‐solvated infinite chain. Crystal structures of the first magnesiate examples of this amide in [MMg{N(SiMe₃)(Dipp)}₂(μ‐nBu)]_∞ (M=Na or K) are also revealed, though these breakdown to their homometallic components in donor solvents as revealed through NMR and DOSY studies.     

Azido­[1,1′‐bis­(di­phenyl­phosphino)­ferrocene](penta­methyl­cyclo­penta­dienyl)­rhodium(III) hexa­fluoro­phosphate

In the title compound, azido‐2κN‐bis­[μ‐(1η⁵:2κP)‐di­phenyl­phosphino­cyclo­penta­dienyl][2(η⁵)‐penta­methyl­cyclo­penta­di­enyl]­iron(III)­rhodium(III) hexa­fluoro­phosphate, [{Rh(C₁₀H₁₅)(N₃)}{Fe(μ‐C₁₇H₁₄P)₂}]PF₆ or [FeRh(C₁₀H₁₅)(μ‐C₁₇H₁₄P)₂(N₃)]PF₆, the coordination sphere of Rh^III can be described as pseudo‐tetrahedral, composed of two P atoms from a 1,1′‐bis­(di­phenyl­phosphino)­ferrocene (dppf) ligand, an azido N atom and the centroid of the ring of a C₅Me₅ (Cp*) ligand. The two cyclo­penta­dienyl rings in the dppf moiety adopt an eclipsed conformation. The Rh⋯Fe distance is 4.340 (2) Å.