Practical Synthesis of p‐ and o‐Amino‐ and Methoxyphenolic Anthraquinones

New versatile and selective methods for the syntheses of substituted amino‐ and methoxyphenolic anthraquinones ( I–IV ) based on fusion of cyanophthalides ( V ) and semiquinone aminals ( VI , VII ) under basic conditions are described.     

Substituent effects in the Diels–Alder reactions of butadienes,cyclopentadienes, furans and pyroles with maleic anhydride

In this study, activation energies in the Diels–Alder reactions of a series of substituted butadienes, cyclopentadienes, furans and pyroles with maleic anhydride were calculated by the M06‐2X/6‐31G(d) method. The substituent effects on the reactivity and the endo–exo selectivity have been examined. The strength of reactivity effect has an order of pyroles > furans > cyclopentadienes > butadienes, which is highly correlated with the lowest unoccupied molecular orbital energy, the electronic chemical potential and the electrophilicity of parent diene but relatively less correlated with the highest occupied molecular orbital energy and chemical hardness. The trend that an increase of necleophilicity caused by an electron‐donating group on the diene favors the endo TS is effective with C2 substitution. With C1 substitution, the trend is ambiguous or even opposite. Copyright © 2015 John Wiley & Sons, Ltd.     

New N,S-Substituted Dienes from Mono(thio)substituted-2-nitrohalo-1,3-diene and Some Amines

Mono(thio)substituted nitrodiene compound 1 reacted with 2a–f and yielded 3a–f in methylene chloride. Compound 1 gave 7 by the reaction with 6. Compounds 5a–c were obtained by the reactions of 4a–c with 1. 3a also has been structurally characterized using single-crystal X-ray diffraction analyses.     

One Step Synthesis of 1,4-Dialkyl-1,4-Diphospha 2,3,5,6-Tetra -Hydroxycyclohexanes from Primary Alkylphosphines and Glyoxal

Abstract

High yields of 1,4-dialkyl 1,4-diphospha 2,3,5,6 tetrahydroxycyclohexanes are produced when equal molar portions of glyoxal are added to primary alkylphosphines. The reactions take place at low temperatures and without the aid of an acid catalyst. The cyclic products are readily converted to the corresponding 1,4 diphosphoryl or dithiophosphoryl derivatives with the addition of a slight excess of H₂O₂ or sulphur. Of particular importance are the order and rates of addition of the two reagents. Reversal of the addition of the reagents results in an entirely different product. This synthesis offers an easy route to 1,4-diphosphacyclohexanes. In addition, the oxides of the lower homologs have utility as flame retardants for polymethymethacrylate and other plastics.     

Synthesis and fluorescent properties of conjugated copolymers containing maleimide and fluorene units at the main chain

Yamamoto or Suzuki–Miyaura coupling polymerizations of 2,3‐diiodo‐N‐cyclohexylmaleimide with fluorene derivatives (2,7‐dibromo‐9,9′‐dihexylfluorene and 9,9′‐dihexylfluorene‐2,7‐diboronic acid) were carried out. The number‐average molecular weights (M_n) of the resulting copolymers were 2600–3500 by gel permeation chromatography analysis. The fluorescence emission of the alternating copolymer showed the emission maxima at 551 nm in THF. On the other hand, the random copolymers showed the bimodal emission peaks at 418–420 and 555–557 nm region, respectively. The fluorescence peaks of the random copolymers on the long wavelength region (555–557 nm) were attributed to the conjugated neighboring N‐cyclohexylmaleimide‐9,9′‐dihexylfluorene units in the polymer main chain. Furthermore, the copolymers exhibited the fluorescence solvatochromism by the difference of the polarity of solvents. The alternating and random copolymers showed the different fluorescence solvatochromism, and the emission colors are distinguishable by the naked eye, respectively. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4945–4956     

Organocatalytically Enantioselective Approach to Polysubstituted Tetrahydropyridines and Piperidines

A convenient and highly enantioselective method for assembly of functionalized 1,2,3,4,5‐pentasubstituted tetrahydropyridines and piperidines was developed. This method relies on preparing the required enantiopure cyclic semi‐acetals via an organocatalyzed Michael addition/cyclization cascade reaction of aldehydes and α‐keto‐α,β‐unsaturated esters, and subsequent reductive amination/condensation with primary amines.     

Characterization of acidity in [B], [Al], and [Ga] isomorphously substituted ZSM‐5: Embedded DFT/UFF approach

The structure and electronic properties of the Brønsted acid site in B, Al or Ga isomorphously substituted ZSM‐5 zeolites were studied by using quantum cluster and embedded ONIOM approaches. In the former approach, zeolites are modeled by 5T and 12T quantum clusters, where T represents a Si or Al atom. In the latter model, called “Embedded ONIOM”, the long‐range interactions of the zeolite lattice beyond the 12T quantum cluster is included via optimized point charges added to the ONIOM(B3LYP/6‐31G(d,p):UFF). Inclusion of the extended zeolitic framework covering the nanocavity has an effect on the structure and adsorption properties. We found that the OH distances and v OH of the acidic proton in zeolite obtained from both models can predict the trend of acid strength as: B‐ZSM‐5 < Ga‐ZSM‐5 < Al‐ZSM‐5, which is in very good agreement with the experimental sequence. Furthermore, the PA data calculated from E‐ONIOM is also consistent with the experimental trend: B‐ZSM‐5 < Ga‐ZSM‐5 < Al‐ZSM‐5. It has, therefore, been demonstrated that our embedded ONIOM model provides accurate performance and can be one of the useful and affordable methods for future mechanistic studies involving petrochemical reactions. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Synthesis and characterization of asymmetric substituted dicarbamates

Several new asymmetric substituted dicarbamates were synthesized with a convenient route.Firstly,tolylene-2,4-diisocyanate dimmer was obtained from monomer with tributylphosphine as catalyst.Then,the dimmer reacted with alcohol(R~1OH) to prepare carbamate substituted uretidione.Finally,uretidione ring was opened and the released isocyanate reacted with another alcohol (R~2OH,R~1≠R~2).     

Synthesis of Functionalized Diethyl(pyrrolidin-2-yl)phosphonate and Diethyl(5-oxopyrrolidin-2-yl)phosphonate

Short and efficient syntheses of functionalized (pyrrolidin-2-yl)phosphonate and (5-oxopyrrolidin-2-yl)phosphonate have been developed. The synthetic strategy involved the diastereospecific 1,3-dipolar cycloaddition of N-benzyl-C-(diethoxyphosphoryl)nitrone to cis-1,4-dihydroxybut-2-ene and dimethyl maleate, respectively. O,O-Diethyl 3-carbamoyl-4-hydroxy(5-oxopyrrolidin-2-yl)phosphonate was obtained from O,O-diethyl 2-benzyl-4,5-dimethoxycarbonyl(isoxazolidin-3-yl)phosphonate by hydrogenation and subsequent treatment with ammonia, whereas transformation of O,O-diethyl 2-benzyl-4,5-dihydroxymethyl(isoxazolidin-3-yl)phosphonate into O,O-diethyl 3-aminomethyl-4-hydroxy(pyrrolidin-2-yl)phosphonate was accomplished by mesylation followed by hydrogenolysis to undergo intramolecular cyclization and the introduction of amino group via ammonolysis. Stereochemistry of the isoxazolidine cycloadducts, as well as the final functionalized (pyrrolidin-2-yl)- and (5-oxopyrrolidin-2-yl)phosphonates were established based on conformational analyses using vicinal H–H, H–P, and C–P couplings and supported by the observed diagnostic NOESY correlation signals.