Highly trans‐1,4‐specific polymerization of 1,3‐butadiene catalyzed by [2,6‐bis{(4S)‐ (−)‐isopropyl‐2‐oxazolin‐2‐yl}pyridine] chromium complex activated with modified methylaluminoxane

Chromium complexes with N,N,N‐tridentate ligands, LCrCl₃ (L = 2,6‐bis{(4S)‐(?)‐isopropyl‐2‐oxazolin‐2‐yl}pyridine ( 1 ), 2,2′:6′,2″‐terpyridine ( 2 ), and 4,4′,4″‐tri‐tert‐butyl‐2,2′:6′,2″‐terpyridine ( 3 )), were prepared. The structures of 1 and 2 were determined by X‐ray crystallography. Upon activation with modified methylaluminoxane (MMAO), 1 catalyzed the polymerization of 1,3‐butadiene, while 2 and 3 was inactive. The obtained poly(1,3‐butadiene) obtained with 1 ‐MMAO was found to have completely trans‐1,4 structure. The 1 ‐MMAO system also showed catalytic activity for the polymerization of isoprene to give polyisoprene with trans‐1,4 (68%) and cis‐1,4 (32%) structure. Copyright © 2011 Society of Chemical Industry     

Highly Enantioselective Phase‐Transfer Catalytic α‐Alkylation of α‐tert‐Butoxycarbonyllactams: Construction of β‐Quaternary Chiral Pyrrolidine and Piperidine Systems

A new enantioselective α‐alkylation of α‐tert‐butoxycarbonyllactams for the construction of β‐quaternary chiral pyrrolidine and piperidine core systems is reported. α‐Alkylations of N‐methyl‐α‐tert‐butoxycarbonylbutyrolactam and N‐diphenylmethyl‐α‐tert‐butoxycarbonylvalerolactam under phase‐transfer catalytic conditions (solid potassium hydroxide, toluene, −40 °C) in the presence of (S,S)‐3,4,5‐trifluorophenyl‐3,3′,5,5′‐tetrahydro‐2,6‐bis(3,4,5‐trifluorophenyl)‐4,4′‐spirobi[4H‐dinaphth[2,1‐c:1′,2′‐e]azepinium] bromide [(S,S)‐NAS Br] (5 mol%) afforded the corresponding α‐alkyl‐α‐tert‐butoxycarbonyllactams in very high chemical (up to 99%) and optical yields (up to 98% ee). Our new catalytic systems provide attractive synthetic methods for pyrrolidine‐ and piperidine‐based alkaloids and chiral intermediates with β‐quaternary carbon centers.     

Synthesis and Biological Evaluation of Pyrrolo[2,1‐f][1,2,4]triazine C‐Nucleosides with a Ribose, 2′‐Deoxyribose,and 2′,3′‐Dideoxyribose Sugar Moiety

The synthesis of hitherto unknown pyrrolo[2,1‐f][1,2,4]triazine C‐nucleosides is described. Structural variations (chlorine, bromine, iodine, and cyano groups) were introduced at position 7 of 4‐aza‐7,9‐dideazaadenine. In addition, pyrrolo[2,1‐f][1,2,4]triazine C‐nucleosides bearing a 2′‐deoxy‐, 2′,3′‐dideoxy‐, and 2′,3′‐dehydrodideoxyribose moiety were also prepared. Among these analogues, the pyrrolo[2,1‐f][1,2,4]triazine C‐ribonucleosides with either a hydrogen atom or cyano group at position 7 of the nucleobase displayed potent cytotoxic activity in a panel of various cancer cell lines.     

Bis(3,5‐dimethylphenyl)‐(S)‐pyrrolidin‐2‐ylmethanol: an Improved Organocatalyst for the Asymmetric Epoxidation of α,β‐Enones

The asymmetric epoxidation of α,β‐enones by the readily available bis(3,5‐dimethylphenyl)‐(S)‐pyrrolidin‐2‐ylmethanol and tert‐butyl hydroperoxide (TBHP) is described. Stereoelectronic substitution on the aryl moiety of diaryl‐2‐pyrrolidinemethanols was found to significantly affect the efficiency with respect to the previously reported (S)‐diphenyl‐2‐pyrrolidinemethanol. Improved reactivity and enantioselectivity were achieved with bis(3,5‐dimethylphenyl)‐(S)‐pyrrolidin‐2‐ylmethanol at reduced catalyst loading (20 mol %) with ees up to 94% for chalcone epoxides under mild reaction conditions, whereas (S)‐diphenyl‐2‐pyrrolidinemethanol afforded a maximum ee of 80%. Interestingly, the methodology is applicable to the epoxidation of more challenging aliphatic or enolizable enones with good control of the asymmetric induction (up to 87% ee).     

Highly Efficient and Enantioselective Iridium‐Catalyzed Asymmetric Hydrogenation of N‐Arylimines

A catalytic method employing the cationic iridium‐(S_c,R_p)‐DuanPhos [(1R,1′R,2S,2′S)‐2,2′‐di‐tert‐butyl‐2,2′,3,3′‐tetrahydro‐1H,1′H‐1,1′‐biisophosphindole] complex and BARF {tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate} counterion effectively catalyzes the enantioselective hydrogenation of acyclic N‐arylimines with high turnover numbers (up to 10,000 TON) and excellent enantioselectivities (up to 98% ee), achieving the practical synthesis of chiral secondary amines.     

Highly Enantioselective Michael Addition Reactions of 3‐Substituted Benzofuran‐2(3H)‐ones to Chalcones Catalyzed by a Chiral Alkyl‐Substituted Thiourea

A highly enantioselective Michael addition of 3‐substituted benzofuran‐2(3H)‐ones to chalcones catalyzed by a chiral bifunctional thiourea was developed. Several chiral 3,3′‐substituted benzofuran‐2(3H)‐ones derivatives, bearing adjacent quaternary‐tertiary stereocenters, were efficiently synthesized with excellent enantioselectivities.     

Diastereo‐ and Enantioselective Synthesis of Chiral Pyrrolidine‐Fused Spirooxindoles via Organocatalytic [3+2] 1,3‐Dipolar Cycloaddition of Azomethine Ylides with Maleimides

In the presence of a Cinchona alkaloid‐based squaramide organocatalyst, the [3+2] cycloaddition of isatin‐derived azomethine ylides with maleimides proceeded readily, thus delivering the desired pyrrolidine‐fused spirooxindoles in 61–89% yields with >20:1 dr and 12 to >99 % ee. The absolute configuration of 5‐chloro‐1,5′‐dimethyl‐3′‐phenyl‐3′,3a′‐dihydro‐2′H‐spiro[indoline‐3,1′‐pyrrolo[3,4‐c]pyrrole]‐2,4′,6′(5′H,6a′H)‐trione was unambiguously determined by means of X‐ray single crystal structure analysis. The reaction mechanism was hypothesized to account for the enantioselective formation of 5‐chloro‐1,5′‐dimethyl‐3′‐phenyl‐3′,3a′‐dihydro‐2′H‐spiro[indoline‐3,1′‐pyrrolo[3,4‐c]pyrrole]‐2,4′,6′(5′H,6a′H)‐trione.

     

苯并呋喃酮在抑制聚丙烯降解过程中的作用

采用多次挤出的方法对三种不同结构苯并呋喃酮与受阻酚及亚磷酸酯的三元复配稳定体系在等规聚丙烯 (PP)中的稳定化作用进行了研究。结果表明:含5,7-二叔丁基-3-(3,4-二甲基苯基)-3氢-苯并呋喃-2-酮 (OXBF1)的复配体系3#配方5次挤出之后的熔体流动速率相对于其同分异构体5,7-二叔丁基-3-(2,5-二甲基苯基)-3氢-苯并呋喃-2-酮(PXBF1)、5,7-二叔丁基-3-(2,4-二甲基苯基)-3氢-苯并呋喃-2-酮 (MXBF1)复配体系的5#配方和6#配方分别下降了24．8％和26％;并且,其抑制所稳定PP加工发黄的作用优于其他两种结构,使得3#配方5次挤出之后的黄度指数(YI)相对于5#配方和6#配方分别下降了9．3％和11．9％;此外,亚磷酸酯对氢过氧化物的还原作用同样提高了苯并呋喃酮高温含氧条件下在PP中的热氧稳定化作用。     

1‐(1H‐Indol‐3‐yl)ethanamine Derivatives as Potent Staphylococcus aureus NorA Efflux Pump Inhibitors

The synthesis of 37 1‐(1H‐indol‐3‐yl)ethanamine derivatives, including 12 new compounds, was achieved through a series of simple and efficient chemical modifications. These indole derivatives displayed modest or no intrinsic anti‐staphylococcal activity. By contrast, several of the compounds restored, in a concentration‐dependent manner, the antibacterial activity of ciprofloxacin against Staphylococcus aureus strains that were resistant to fluoroquinolones due to overexpression of the NorA efflux pump. Structure–activity relationships studies revealed that the indolic aldonitrones halogenated at position 5 of the indole core were the most efficient inhibitors of the S. aureus NorA efflux pump. Among the compounds, (Z)‐N‐benzylidene‐2‐(tert‐butoxycarbonylamino)‐1‐(5‐iodo‐1H‐indol‐3‐yl)ethanamine oxide led to a fourfold decrease of the ciprofloxacin minimum inhibitory concentration against the SA‐1199B strain when used at a concentration of 0.5 mg L ^?1. To the best of our knowledge, this activity is the highest reported to date for an indolic NorA inhibitor. In addition, a new antibacterial compound, tert‐butyl (2‐(3‐hydroxyureido)‐2‐(1H‐indol‐3‐yl)ethyl)carbamate, which is not toxic for human cells, was also found.     

Synthesis of (3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl) propionate derivatives and their thermal antioxidation behavior for POM

Polyoxymethylene (POM) has been widely utilized in industry due to its light weight properties in engineering plastics. At present, POM applications are expanding into the car industry, especially in fuel tanks. Hindered alkyl phenol derivatives have been used as antioxidants for POM; however, these compounds are easily extracted by solvents. Two antioxidants with new structures (N,N′‐triethylenedioxy‐bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylhydrocinnamamide) and N,N′,N′‐tris[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyl‐3‐oxapentyl]melamine) were synthesized and characterized, and their performance as antioxidants for POM was investigated in the present study. The results revealed that N,N′‐triethylenedioxy‐bis(3‐tert‐butyl‐4‐hydroxy‐5‐methylhydrocinnamamide) has good heat aging resistance compared to existing antioxidants for POM, and N,N′,N′‐tris[(3‐tert‐butyl‐4‐hydroxy‐5‐methylphenyl)propionyl‐3‐oxa‐pentyl]melamine has good extraction resistance against solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis,Thermal Stability and Impact Stability of Novel Tetranitro‐Dipyridotetraazapentalene Derivatives

The synthetic details for the construction of three new dipyridotetraazapentalene derivatives, 5H‐pyrido[3″,4″:4′,5′] [1,2,3]triazolo‐ [1′,2′:1,2][1,2,3]triazolo[5,4‐b]pyridin‐6‐ium inner salt ( 8 ), 5H‐pyrido[3″,2″:4′,5′] [1,2,3]triazolo[1′,2′:1,2] [1,2,3]triazolo[5,4‐b]‐pyridin‐6‐ium inner salt ( 15 ) and 5H‐pyrido[2″,3″:4′,5′] [1,2,3]‐triazolo[1′,2′:1,2][1,2,3]triazolo[4,5‐b]pyridin‐6‐ium inner salt ( 16 ) are presented. Nitration of ( 8 ) and ( 15 ) afforded the novel tetranitrodipyridotetraazapentalene derivatives, 2,4,8,10‐tetranitro‐5H‐pyrido[3″,4″:4′,5′][1,2,3]triazolo[1′,2′:1,2][1,2,3]‐triazolo[5,4‐b]‐pyridin‐6‐ium inner salt ( 3 ) and 2,4,8,10‐tetranitro‐5H‐pyrido[3″,2″:4′,5′][1,2,3]triazolo[1′,2′:1,2][1,2,3]‐triazolo[5,4‐b]‐pyridin‐6‐ium inner salt ( 4 ) in good yields. Both isomers, ( 3 ) and ( 4 ), exhibited high thermal stability (differential scanning calorimetric analysis and thermal gravimetric analysis) and were insensitive to impact (hammer/anvil test).     

Synthesis and spectroelectrochemistry of dithieno(3,2‐b:2′,3′‐d)pyrrole derivatives

New π‐conjugated polymers containing dithieno(3,2‐b:2′,3′‐d)pyrrole (DTP) were successfully synthesized via electropolymerization. The effect of structural differences on the electrochemical and optoelectronic properties of the 4‐[4H‐dithieno(3,2‐b:2′,3′‐d)pyrrol‐4‐yl]aniline (DTP–aryl–NH₂), 10‐[4H‐dithiyeno(3,2‐b:2′,3′‐d)pirol‐4‐il]dekan‐1‐amine (DTP–alkyl–NH₂), and 1,10‐bis[4H‐dithieno(3,2‐b:2′,3′‐d)pyrrol‐4‐yl] decane (DTP–alkyl–DTP) were investigated. The corresponding polymers were characterized by cyclic voltammetry, NMR (¹H‐NMR and ¹³C‐NMR), and ultraviolet–visible spectroscopy. Changes in the electronic nature of the functional groups led to variations in the electrochemical properties of the π‐conjugated systems. The electroactive polymer films revealed redox couples and exhibited electrochromic behavior. The replacement of the DTP–alkyl–DTP unit with DTP–aryl–NH₂ and DTP–alkyl–NH₂ resulted in a lower oxidation potential. Both the poly(10‐(4H‐Dithiyeno[3,2‐b:2′,3′‐d]pirol‐4‐il)dekan‐1‐amin) (poly(DTP–alkyl–NH₂)) and poly(1,10‐bis(4H‐dithieno[3,2‐b:2′,3′‐d]pyrrol‐4‐yl) decane) (poly(DTP–alkyl–DTP)) films showed multicolor electrochromism and also fast switching times (<1 s) in the visible and near infrared regions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40701.     

Synthesis and Cytostatic and Antiviral Activities of 2′‐Deoxy‐2′,2′‐difluororibo‐ and 2′‐Deoxy‐2′‐fluororibonucleosides Derived from 7‐(Het)aryl‐7‐deazaadenines

A series of sugar‐modified derivatives of cytostatic 7‐heteroaryl‐7‐deazaadenosines (2′‐deoxy‐2′‐fluororibo‐ and 2′‐deoxy‐2′,2′‐difluororibonucleosides) bearing an aryl or heteroaryl group at position 7 was prepared and screened for biological activity. The difluororibonucleosides were prepared by non‐ stereoselective glycosidation of 6‐chloro‐7‐deazapurine with benzoyl‐protected 2‐deoxy‐2,2‐difluoro‐D ‐erythro‐pentofuranosyl‐1‐mesylate, followed by amination and aqueous Suzuki cross‐couplings with (het)arylboronic acids. The fluororibo derivatives were prepared by aqueous palladium‐catalyzed cross‐coupling reactions of the corresponding 7‐iodo‐7‐deazaadenine 2′‐deoxy‐2′‐fluororibonucleoside 20 with (het)arylboronic acids. The key intermediate 20 was prepared by a six‐step sequence from the corresponding arabinonucleoside by selective protection of 3′‐ and 5′‐hydroxy groups with acid‐labile groups, followed by stereoselective S_N2 fluorination and deprotection. Some of the title nucleosides and 7‐iodo‐7‐deazaadenine intermediates showed micromolar cytostatic or anti‐HCV activity. The most active were 7‐iodo and 7‐ethynyl derivatives. The corresponding 2′‐deoxy‐2′,2′‐difluororibonucleoside 5′‐O‐triphosphates were found to be good substrates for bacterial DNA polymerases, but are inhibitors of human polymerase α.     

The Use of an Unusual Rearrangement Sequence for the Syntheses of 3‐(1‐Aminoalkylidene)‐3H‐thiophen‐2‐ones and two Examples of their Surprising Electrophilic‐Induced Dimerization Reactions

The reaction of 2‐amino‐3‐carbomethoxythiophene ( 1a ) and 2‐amino‐3‐carboethoxy‐4,5‐dimethylthiophene ( 1b ) with methyl‐ or ethylmagnesium chloride leads to new 3‐(1‐aminoalkylidene)‐3H‐thiophen‐2‐ones 4a—d in good yields (60—87%). Treatment of the compounds 4a and 4c with catalytic amounts of p‐TsOH in boiling CHCl₃ afforded the (±)‐4,4′‐bis‐(1‐aminoalkylidene)‐3′,4′‐4H,2′H‐[2,3′]bithiophenyl‐5,5′‐diones 9a and 9b as new interesting heterocycles in preparatively useful yields (60/mdash;65%).     

Catalytic Non‐Enzymatic Kinetic Resolution

While tremendous advances have been made in asymmetric synthesis, the resolution of racemates is still the most important industrial approach to the synthesis of chiral compounds. The use of enzymes for the kinetic resolution (KR) of racemic substrates to afford enantiopure compounds in high enantioselectivity and good yield has long been a popular strategy in synthesis. However, transition metal‐mediated and more recently organocatalyzed KRs have gained popularity within the synthetic community over the last two decades due to the progress made in the development of chiral catalysts for asymmetric reactions. Many catalytic non‐enzymatic procedures have been developed providing high enantioselectivity and yield for both products and recovered starting materials. Indeed, the non‐enzymatic KR of racemic compounds based on the use of a chiral catalyst is presently an area of great importance in asymmetric organic synthesis. The goal of this review is to provide an update on the principal developments of catalytic non‐enzymatic KR covering the literature since 2004. This review is subdivided into seven sections, according to the different types of compounds that have been resolved through catalytic non‐enzymatic KR, such as alcohols, epoxides, amines, alkenes, carbonyl derivatives, sulfur compounds and ferrocenes. Abbreviations: Ac: acetyl; acac: acetylacetone; AQN: anthraquinone; Ar: aryl; Atm: atmosphere; BINAM: 1,1′‐binaphthalenyl‐2,2′‐diamine; BINAP: 2,2′‐bis(diphenylphosphanyl)‐1,1′‐binaphthyl; BINEPINE: phenylbinaphthophosphepine; BINOL: 1,1′‐bi‐2‐naphthol; Bmim: 1‐butyl‐3‐methylimidazolium; Bn: benzyl; Boc: tert‐butoxycarbonyl; Box: bisoxazoline; BSA: bis(trimethylsilyl)acetamide; Bu: butyl; Bz: benzoyl; c: cyclo; CBS: Corey–Bakshi–Shibata; Cbz: benzyloxycarbonyl; COD: cyclooctadiene; COE: cyclooctene; Cy: cyclohexyl; Dba: (E,E)‐dibenzylideneacetone; DBU: 1,8‐diazabicyclo[5.4.0]undec‐7‐ene; DCC: N,N′‐dicyclohexylcarbodiimide; de: diastereomeric excess; DEAD: diethyl azodicarboxylate; Dec: decanyl; DHQD: dihydroquinidine; Difluorphos: 5,5′‐bis(diphenylphosphino)‐2,2,2′,2′‐tetrafluoro‐4,4′‐bi‐1,3‐benzodioxole; DIPEA: diisopropylethylamine: DKR: dynamic kinetic resolution; DMAP: 4‐dimethylaminopyridine; DMSO: dimethyl sulfoxide; DNA: deoxyribonucleic acid; DOSP: N‐(dodecylbenzenesulfonyl)prolinate; DTBM: di‐tert‐butylmethoxy; ee: enantiomeric excess; Et: ethyl; equiv.: equivalent; Fu: furyl; Hex: hexyl; HIV: human immunodeficiency virus; HMDS: hexamethyldisilazide; KR: kinetic resolution; L: ligand; LDA: lithium diisopropylamide; MAO: methylaluminoxane; Me: methyl; Ms: mesyl; MTBE: methyl tert‐butyl ether; Naph: naphthyl; nbd: norbornadiene; NBS: N‐bromosuccinimide; NIS: N‐iodosuccinimide; Pent: pentyl; Ph: phenyl; Piv: pivaloyl; PMB: p‐methoxybenzoyl; Pr: propyl Py: pyridyl; r.t.: room temperature; s: selectivity factor; Segphos: 5,5′‐bis(diphenylphosphino)‐4,4′‐bi‐1,3‐benzodioxole; (S,S′,R,R′)‐Tangphos: (1S,1S′,2R,2R′)‐1,1′‐di‐tert‐butyl‐(2,2′)‐diphospholane; TBS: tert‐butyldimethylsilyl; TBDPS: tert‐butyldiphenylsilyl; TCCA: trichloroisocyanuric acid ; TEA: triethylamine; TEMPO: tetramethylpentahydropyridine oxide; THF: tetrahydrofuran; Thio: thiophene; Tf: trifluoromethanesulfonyl; TMS: trimethylsilyl; Tol: tolyl; Ts: 4‐toluenesulfonyl (tosyl)     

Recent Developments in Enantioselective Metal‐Catalyzed Domino Reactions

Since the first definition of domino reactions by Tietze in 1993, an explosive number of these fascinating reactions has been developed, allowing the easily building of complex chiral molecular architectures from simple materials to be achieved in a single step. Even more interesting, the possibility to join two or more reactions in one asymmetric domino process catalyzed by chiral metal catalysts has rapidly become one challenging goal for chemists, due to economical advantages, such as avoiding costly protecting groups and time‐consuming purification procedures after each step. The explosive development of enantioselective metal‐catalyzed domino including multicomponent reactions is a consequence of the considerable impact of the advent of asymmetric transition metal catalysis. This review aims to update the last developments of enantioselective one‐, two‐ and multicomponent domino reactions mediated by chiral metal catalysts, covering the literature since the beginning of 2006. Abbreviations: Ac: acetyl; AQN: anthraquinone; Ar: aryl; bdpp: 2,4‐bis(diphenylphosphino)pentane; BINAP: 2,2′‐bis(diphenylphosphino)‐1,1′‐binaphthyl; BINEPINE: phenylbinaphthophosphepine; BINIM: binapthyldiimine; BINOL: 1,1′‐bi‐2‐naphthol; BIPHEP: 2,2′‐bis(diphenylphosphino)‐1,1′‐biphenyl; Bn: benzyl; Boc: tert‐butoxycarbonyl; Box: bisoxazoline; BOXAX: 2,2′‐bis(oxazolyl)‐1,1′‐binaphthyl; BPTV: N‐benzene‐fused phthaloyl‐valine; Bu: butyl; Bz: benzoyl; Cat: catechol; Chiraphos: 2,3‐bis(diphenylphosphine)butane; cod: cyclooctadiene; Cy: cyclohexyl; DABCO: 1,4‐diazabicyclo[2.2.2]octane; dba: (E,E)‐dibenzylideneacetone; DBU: 1,8‐diazabicyclo[5.4.0]undec‐7‐ene; DCE: dichloroethane; de: diastereomeric excess; DHQ: hydroquinine; DHQD: dihydroquinidine; DIFLUORPHOS: 5,5′‐bis(diphenylphosphino)‐2,2,2′,2′‐tetrafluoro‐4,4′‐bi‐1,3‐benzodioxole; DIPEA: diisopropylethylamine; DMF: dimethylformamide; DMSO: dimethyl sulfoxide; DOSP: N‐p‐dodecylbenzenesulfonylprolinate; DPEN: 1,2‐diphenylethylenediamine; dtb: di‐tert‐butyl; dtbm: di‐tert‐butylmethoxy; E: electrophile; ee: enantiomeric excess; Et: ethyl; FBIP: ferrocene bis‐imidazoline bis‐palladacycle; Fc: ferrocenyl; FOXAP: ferrocenyloxazolinylphosphine; Hex: hexyl; HFIP: hexafluoroisopropyl alcohol; HMPA: hexamethylphosphoramide; iPr‐DuPhos: 1,2‐bis(2,5‐diisopropylphospholano)benzene; Josiphos: 1‐[2‐(diphenylphosphino)ferrocenyl]ethyldicyclohexylphosphine ethanol adduct; L: ligand; MCPBA: 3‐chloroperoxybenzoic acid; Me: methyl; Me‐DuPhos: 1,2‐bis(2,5‐dimethylphospholano)benzene; MEDAM: bis(dimethylanisyl)methyl; MOM: methoxymethyl; Naph: naphthyl; NMI: N‐methylimidazole; MWI: microwave irradiation; Norphos: 2,3‐bis(diphenylphosphino)‐bicyclo[2.2.1]hept‐5‐ene; Ns: nosyl (4‐nitrobenzene sulfonyl); Nu: nucleophile; Oct: octyl; Pent: pentyl; Ph: phenyl; PHAL: 1,4‐phthalazinediyl; Pin: pinacolato; PINAP: 4‐[2‐(diphenylphosphino)‐1‐naphthalenyl]‐N‐[1‐phenylethyl]‐1‐phthalazinamine; Pr: propyl; Py: pyridyl; PYBOX: 2,6‐bis(2‐oxazolyl)pyridine; QUINAP: 1‐(2‐diphenylphosphino‐1‐naphthyl)isoquinoline; QUOX: quinoline‐oxazoline; Segphos: 5,5′‐bis(diphenylphosphino)‐4,4′‐bi‐1,3‐benzodioxole; Solphos: 7,7′‐bis(diphenylphosphino)‐3,3′,4,4′‐tetrahydro‐4,4′‐dimethyl‐8,8′‐bis‐2H‐1,4‐benzoxazine; SPRIX: spirobis(isoxazoline); SYNPHOS: 6,6′‐bis(diphenylphosphino)‐2,2′,3,3′‐tetrahydro‐5,5′‐bi‐1,4‐benzodioxin; Taniaphos: [2‐diphenylphosphinoferrocenyl](N,N‐dimethylamino)(2‐diphenylphosphinophenyl)methane; TBS: tert‐butyldimethylsilyl; TC: thiophene carboxylate; TCPTTL: N‐tetrachlorophthaloyl‐tert‐leucinate; TEA: triethylamine; Tf: trifluoromethanesulfonyl; TFA: trifluoroacetic acid; THF: tetrahydrofuran; TMS: trimethylsilyl; Tol: tolyl; Ts: 4‐toluenesulfonyl (tosyl); C₃‐Tunephos: 1,13‐bis(diphenylphosphino)‐7,8‐dihydro‐6H‐dibenzo[f,h][1,5]dioxonin; VAPOL: 2,2′‐diphenyl‐[3,3′‐biphenanthrene]‐4,4′‐diol     

Gold(I)‐Catalyzed Intramolecular Hydroamination of N‐Allylic N′‐Arylureas to form Imidazolidin‐2‐ones

Treatment of N‐allylic N′‐arylureas with a catalytic 1:1 mixture of di‐tert‐butyl‐o‐biphenylphoshphine gold(I) chloride and silver hexafluorophosphate (1 mol%) in chloroform at room temperature led to 5‐exo‐hydroamination to form the corresponding imidazolidin‐2‐ones in excellent yield. In the case of N‐allylic ureas that possessed an allylic alkyl, benzyloxymethyl, or acetoxymethyl substituent, gold(I)‐catalyzed 5‐exo‐hydroamination leads to formation of the corresponding trans‐3,4‐disubstituted imidazolidin‐2‐ones in excellent yield with ≥50:1 diastereoselectivity.     

Thermal and Mechanical Properties of Poly(arylene ether ketone)s Based on 5‐tert‐Butyl‐1,3‐bis(4‐fluorobenzoyl)benzene

An aromatic bishalide, 5‐tert‐butyl‐1,3‐bis(4‐fluorobenzoyl)benzene ( 2 ) was synthesized in high yield and purity by the reaction of 5‐tert‐butylisophthaloyl chloride ( 1 ) and fluorobenzene and polymerized by nucleophilic substitution reaction with commercially available aromatic bisphenols to prepare a series of high molecular weight poly(arylene ether ketone)s containing pendant tertiary butyl groups. The effect of molecular structure on the physical, thermal, mechanical and adhesion properties of the polymers was investigated.     

Synthesis and Antiviral Evaluation of TriPPPro‐AbacavirTP,TriPPPro‐CarbovirTP,and Their 1′,2′‐cis‐Disubstituted Analogues

Herein we describe the synthesis of lipophilic triphosphate prodrugs of abacavir, carbovir, and their 1′,2′‐cis‐substituted carbocyclic analogues. The 1′,2′‐cis‐carbocyclic nucleosides were prepared by starting from enantiomerically pure (1R,2S)‐2‐((benzyloxy)methyl)cyclopent‐3‐en‐1‐ol by a microwave‐assisted Mitsunobu‐type reaction with 2‐amino‐6‐chloropurine. All four nucleoside analogues were prepared from their 2‐amino‐6‐chloropurine precursors. The nucleosides were converted into their corresponding nucleoside triphosphate prodrugs (TriPPPro approach) by application of the H‐phosphonate route. The TriPPPro compounds were hydrolyzed in different media, in which the formation of nucleoside triphosphates was proven. While the TriPPPro compounds of abacavir and carbovir showed increased antiviral activity over their parent nucleoside, the TriPPPro compounds of the 1′,2′‐cis‐substituted analogues as well as their parent nucleosides proved to be inactive against HIV.     

Reactions and polymerization of hexa‐[3‐tert‐butyl‐4‐ hydroxyphenoxy]cyclotriphosphazene: A new method for the preparation of soluble cyclomatrix phosphazene polymers

Novel cyclomatrix phosphazene‐containing polyester polymers were synthesized through the reaction of a polyhydroxylated cyclotriphosphazene and a bifunctional acid chloride. To demonstrate the chemistry of the free hydroxyl of hexa‐[3‐tert‐butyl‐4‐hydroxyphenoxy]cyclotriphosphazene, nucleophilic displacement reactions were performed with both acetic anhydride and alkyl chlorides. This work compares favorably to literature data for the chemistry of hexa‐[4‐hydroxyphenoxy]cyclotriphosphazene, whose hydroxyl is not hindered by an adjacent substituent. The hindered site of hexa‐[3‐tert‐butyl‐4‐hydroxyphenoxy]cyclotriphosphazene was found to react with bidentate acid chlorides to yield new high polymers. The phosphazene‐containing polyesters were observed to have good solubility in polar organic solvents. Characterization of these new materials was performed using dilute solution laser light scattering techniques, thermal analysis, and NMR spectroscopy. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 242–251, 2001