Influence of the Sulfinyl Group on the Chemoselectivity and pi-Facial Selectivity of Diels-Alder Reactions of (S)-2-(p-Tolylsulfinyl)-1,4-benzoquinone

Diels-Alder reactions of (S)-2-(p-tolylsulfinyl)-1,4-benzoquinone (1a) with cyclic (cyclopentadiene and cyclohexadiene) and acyclic dienes (1-[(trimethylsilyl)oxy]-1,3-butadiene and trans-piperylene) under different thermal and Lewis acid conditions are reported. Chemoselectivity (reactions on C(2)-C(3) versus C(5)-C(6) double bonds) is mainly related to the cyclic (on C(5)-C(6)) or acyclic (on C(2)-C(3)) structure of the diene. The high pi-facial selectivity observed could be controlled by choosing adequate experimental conditions.     

From central to helical chirality: synthesis of P and M enantiomers of [5]helicenequinones and bisquinones from (SS)-2-(p-tolylsulfinyl)- 1,4-benzoquinone

The reaction of 1,4-divinyl-1,3-cyclohexadiene, 5,8-dimethoxy- or tert-butyldimethylsilyloxy-3-vinyl-1,2-dihydrophenanthrene or 6-vinyl-7,8-dihydro-1,4-phenanthrenequinone with an excess of enantiopure (SS)-2-(p-tolylsulfinyl)-1,4-benzoquinone (2) led to the direct formation of enantioenriched dihydro[5]helicenequinones or bisquinones (50-->98 % ee). A domino Diels-Alder cycloaddition/sulfoxide elimination/partial aromatization process occurs, being the absolute configuration of the final helicene defined in the aromatization step. Both M and P helimers are accessible through a stepwise enantiodivergent process if the pentacyclic dihydroaromatic intermediate resulting in the two first steps is aromatized in the presence of (+/-)-2, DDQ, CAN or DBU.     

Influence of diene substitution on Diels-Alder reactions between vinyl dihydronaphthalenes and (SS)-2-(p-tolylsulfinyl)-1,4-benzoquinone

The asymmetric Diels-Alder reaction between 2-(E-2-acetoxyvinyl)-8-tert-butyl-3,4-dihydronaphthalene (8) and enantiopure (SS)-2-(p-tolylsulfinyl)-1,4-benzoquinone (1) takes place exclusively on the unsubstituted C(5)-C(6) double bond of (SS)-1 with a very high control of the chemo-, regio-, and diastereoselectivity of the process affording tetracyclic sulfinyl derivative 13a possessing five stereogenic centers. The analogue diene 9, lacking the tert-butyl group, gave a less chemoselective reaction (C(2)-C(3)/C(5)-C(6): 60/40) in favor of reaction through the sulfoxide-substituted double bond C(2)-C(3) of 1. Steric effects of the remote tert-butyl group and electronic factors due to the OAc substituent are controlling the process.     

Diels-alder reactions with 2-(Arylsulfinyl)-1,4-benzoquinones: effect of aryl substitution on reactivity, chemoselectivity, and pi-facial diastereoselectivity

Diels-Alder reactions of (SS)-2-(2'-methoxynaphthylsulfinyl)-1, 4-benzoquinone (1b), 2-(p-methoxyphenylsulfinyl)-1,4-benzoquinone (1c), and 2-(p-nitrophenylsulfinyl)-1,4-benzoquinone (1d) with cyclopentadiene are reported. These cycloadditions allowed the highly chemo- and stereoselective formation of both diastereoisomeric endo-adducts resulting from reaction on the unsubstituted double bond C(5)-C(6) of quinones working under thermal and Eu(fod)(3)- or BF(3).OEt(2)-catalyzed conditions. The synthesis of endo-adduct [4aS,5S,8R,8aR,SS]-9d resulting from cycloaddition on the substituted C(2)-C(3) double bond was achieved in a chemo- and diastereoselective way from quinone 1d in the presence of ZnBr(2). The reactivity and selectivity of the process proved to be dependent on the electron density of the arylsulfinyl group.     

Efficient asymmetric synthesis of [7]helicene bisquinones

The efficient one-pot six-step domino process which occurs when (SS)-2-(p-tolylsulfinyl)-1,4-benzoquinone (1) reacts with 3,6-divinyl-1,2,7,8-tetrahydrophenanthrenes 2a-c allowed enantioselective access to [7]helicene bisquinones 3a-c with excellent optical purities (96 to > 99% ee).     

An Improved and Efficient Preparation of the Chiral NAD(P)H Model (SS)-1-Benzyl-3-(p-tolylsulfinyl)-1,4-dihydropyridine

An improved procedure for the preparation of chiral NAD(P)H model, (SS)-1-benzyl-3-(p-tolylsulfinyl)-1,4-dihydropyridine, with satisfactary chemical yield and excellent enantiopurity is reported.     

Spectrophotometric and fluorescence quenching studies of the charge transfer complexation of (4-dimethylamino-benzylidene)-(4,6-dimethyl-pyrimidin-2-yl)-amine with some organic acceptors

The interaction of organic acceptors such as tetrafluoro-1,4-benzoquinone (p-TFQ), tetrachloro-1,4-benzoquinone (p-TCQ), tetrachloro-1,2-benzoquinone (o-TCQ), tetrabromo-1,4-benzoquinone (p-TBQ), tetrabromo-1,2-benzoquinone (o-TBQ) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) with (4-dimethylamino-benzylidene)-(4,6-dimethyl-pyrimidin-2-yl)-amine (SB) as donor is studied spectrophotometrically and fluoremetrically in dichloromethane and trichloromethane. The association constant (K), thermodynamic parameters (ΔG°, ΔH° and ΔS°), oscillator strength (f), transition dipole moment (μ) and stoichiometric ratio are calculated using Benezi-Hildbrand's, Job and straight-line methods, respectively. The results reveal that the interaction between the donor and acceptors is due to π-π* transitions by the formation of radical ion pairs. The fluorescence quenching of SB with different organic acceptors is investigated. The results reveal that the fluorescence quenching obeys the static type mechanism via charge transfer complex formation in the ground state. The effect of temperature on the equilibrium constants of the CT complexes is also studied.     

Synthesis of 1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-r-benzimidazoles

Reaction of 2,6-di-tert-butyl-1,4-benzoquinone with o-phenylendiamine gives 2,6-di-tert-butyl-1,4-benzoquinone-4-(N-o-aminophenyl)imine which reacts smoothly with heterocyclic, aromatic and aliphatic aldehydes to form (1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-substituted benzimidazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–485, April, 1990.     

First syntheses of 2,2-dimethyl-7-(2'-methylbut-3'-en-2'-yl)-2H-chromen-6-ol and 2-(3'-methylbut-2'-enyl)-5-(2'-methylbut-3'-en-2'-yl)-1,4-benzoquinone, novel prenylated quinone derivatives from the New Zealand brown alga Perithalia capillaris

The first syntheses of 2,2-dimethyl-7-(2'-methylbut-3'-en-2'-yl)-2H-chromen-6-ol (1) and 2-(3'-methylbut-2'-enyl)-5-(2'-methylbut-3'-en-2'-yl)-1,4-benzoquinone (2), novel prenylated quinone derivatives from the New Zealand brown alga Perithalia capillaris, are reported, in which the key steps are consecutive Claisen rearrangements that proceed with both high chemo- and regioselectivity.     

Synthetic transformations of higher terpenoids: XXVIII. Diels-Alder reactions of 16-(trimethylsiloxybutadienyl) labdanoids

15,16-Epoxy-16-(3-trimethylsiloxybuta-1,3-dien-1-yl)labdanoids were synthesized, and their reactions with cyclic dienophiles (1,4-benzoquinone, 1,4-toluquinone, 2-bromo-6-methyl-1,4-benzoquinone, and N-methylmaleimide) were studied. The reactions with unsymmetrically substituted benzoquinones were not selective. Methods for the preparation of hybrid compounds containing furan diterpenoid and substituted naphthoquinone, octahydroisoindoletrione, or hexahydroisoindoledione fragments were proposed.     

Stereoselective alkylidenation of ketones with 2-(p-toluenesulfinyl)benzyl iodide: synthesis of enantiomerically pure trisubstituted epoxides

Alkylidenation of arylmethyl, dialkyl, and cyclic ketones with 2-( p-toluenesulfinyl)benzyl iodide in the presence of NaN(SiMe3)2 takes place with a high or complete control of the facial selectivity at the carbonyl group (up to 98% de) and the carbanion (>98% de), respectively, yielding mixtures of only two optically pure trisubstituted epoxides ( E/Z ratio ranges between 2:1 and >50:1). Removal of the p-tolylsulfinyl group with t-BuLi provides the corresponding (E)-3-phenyl-2,2-disubstituted epoxides without affecting their optical purity.     

Hydrohalogenation of N-acetyl(aroyl)-1,4-benzoquinone monoimines

New N-acetyl-1,4-benzoquinone monoimines alkyl-substituted in the quinoid ring were synthesized. The hydrohalogenation of N-acetyl(aroyl)-1,4-benzoquinone monoimines proceeds exclusively in keeping with the 1,4-addition. The hydrochlorination occurs along the ionic mechanism, in the hydrobromination grows the role of the radical mechanism.     

Iron pentacarbonyl assisted photochemical route to 2,5- and 2,6-divinyl-substituted 1,4-benzoquinones from 1-ene-3-ynes

Photochemical reaction between the enynes, (Z)-1-methoxybut-1-ene-3-yne, 1 or isopropenyl acetylene, 2 with CO in presence of Fe(CO)₅ yields the 2,6- and 2,5-divinyl-substituted 1,4-benzoquinones: 2,6-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (3, 42%), 2,5-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (4, 31.5%), [{η²,η²:2,6-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (5, 45%), and {η²,η²:2,5-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (6, 65%).     

Bridged cyanine dyes. Part 2 . 1-(N-methyl-2-benzothiazolylinio)-3-(N-methyl-2-benzothiazolylene) and 1-(N-methyl-4-pyridinio)-3-(N-methyl-4-pyridylene)cyclopenta-1,4-dienes with fused rings

1,3-Bis(N-methyl-4-pyridyl)- and 1,3-bis(N-methyl-2-benzothiazolyl)-propane diiodides react with 1,2-cyclohexanedione, tetrachloro-1,2- and -1,4-benzoquinone, 2,3-dichloronaphthoquinone, 3,4-dichloromaleimide and 2,3-dichloroquinoxaline to give novel fused ring bridged cyanine dyes.     

Reaction of N-acetyl- and N-[1-(arylsulfonylimino)ethyl]-1,4-benzoquinone imines with sodium arenesulfinates

N-Acetyl- and N-[1-(arylsulfonylimino)ethyl]-1,4-benzoquinone imines having no substituent in the 2- and/or 6-position of the quinoid ring react with sodium arenesulfinates preferentially according to the 1,4-addition pattern. The presence of an ArSO₂N group favors radical ion reaction with formation of 1,6-addition products.     

Synthesis and properties of 2-amino-5-(3,5,6-trichloro-1,4-benzoquinon-2-yl)thiazoles

The reaction of thiourea of N-substituted thioureas with 2-(2-N,N-diethylaminoethenyl)-3,5,6-trichloro-1,4-benzoquinone leads, through the formation of 2,5-dihydroxy-3,4,6,7-tetrachlorocoumaran, to 2-amino-5-(2,5-dihydroxy-3,4,6-trichlorophenyl)thiazoles (which exist in the form of betaines), the oxidation of which leads to 2-amino-5-(3,5,6-trichloro-1,4-benzoquinon-2-yl)thiazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 692–698, May, 1988.     

Efficient trans-selectivity in the cyclocondensation of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde with activated dienes catalyzed by Yb(OTf)3

Reactions of (S)-2-[2-(p-tolylsulfinyl)phenyl]acetaldehyde 1 with Danishefsky's and related dienes took place in the presence of Yb(OTf)3 in a completely stereoselective manner, mediated by a remote sulfinyl group (1,5-asymmetric induction), to afford the corresponding 2,3-dihydro-4H-pyran-4-ones. These reactions followed a stepwise mechanism, as was corroborated by isolation of the corresponding intermediates, with a high level of trans-selectivity for 4-methyl-substituted dienes. Treatment of the adducts with Raney Ni provided concomitant cleavage of the C-S bond and reduction of the conjugated carbonyl grouping.     

Valence-state analysis through spectroelectrochemistry in a series of quinonoid-bridged diruthenium complexes [(acac)(2)Ru(mu-L)Ru(acac)(2)](n) (n=+2, +1, 0, -1, -2)

The quinonoid ligand-bridged diruthenium compounds [(acac)(2)Ru(mu-L(2-))Ru(acac)(2)] (acac(-)=acetylacetonato=2,4-pentanedionato; L(2-)=2,5-dioxido-1,4-benzoquinone, 1; 3,6-dichloro-2,5-dioxido-1,4-benzoquinone, 2; 5,8-dioxido-1,4-naphthoquinone, 3; 2,3-dichloro-5,8-dioxido-1,4-naphthoquinone, 4; 1,5-dioxido-9,10-anthraquinone, 5; and 1,5-diimido-9,10-anthraquinone, 6) were prepared and characterized analytically. The crystal structure analysis of 5 in the rac configuration reveals two tris(2,4-pentanedionato)ruthenium moieties with an extended anthracenedione-derived bis(ketoenolate) pi-conjugated bridging ligand. The weakly antiferromagnetically coupled {Ru(III)(mu-L(2-))Ru(III)} configuration in 1-6 exhibits complicated overall magnetic and EPR responses. The simultaneous presence of highly redox-active quinonoid-bridging ligands and of two ruthenium centers capable of adopting the oxidation states +2, +3, and +4 creates a large variety of possible oxidation state combinations. Accordingly, the complexes 1-6 exhibit two reversible one-electron oxidation steps and at least two reversible reduction processes. Shifts to positive potentials were observed on introduction of Cl substituents (1-->2, 3-->4) or through replacement of NH by O (6-->5). The ligand-to-metal charge transfer (LMCT) absorptions in the visible region of the neutral molecules become more intense and shifted to lower energies on stepwise reduction with two electrons. On oxidation, the para-substituted systems 1-4 exhibit monocation intermediates with intervalence charge transfer (IVCT) transitions of Ru(III)Ru(IV) mixed-valent species. In contrast, the differently substituted systems 5 and 6 show no such near infrared (NIR) absorption. While the first reduction steps are thus assigned to largely ligand-centered processes, the oxidation appears to involve metal-ligand delocalized molecular orbitals with variable degrees of mixing.     

A convenient synthesis and spectroscopic characterization of N, N'-Bis(2-propenyl)-2,7-diazapyrenium quaternary salts

N,N'-Bis(2-propenyl)-2,7-diazapyrenium salts are synthesized in good yield from the reaction of 1,4,5,8-naphthalenetetracarboxylic dianhydride with allylamine, followed by LiAlH(4) reduction and subsequent oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The nature of the counteranion depends on the solvent system used for recrystallization of the crude product from the final DDQ-oxidation step. X-ray analysis shows that if recrystallization is carried out in boiling CH(3)OH/H(2)O (1:1, v/v), the counteranion in the resulting deep-red crystals is always the alkoxy anion of 2-cyano-5,6-dichloro-3-hydroxy-1,4-benzoquinone, whether the final DDQ oxidation ends with addition of HClO(4) or HCl; on the other hand, if recrystallization is carried out with anhydrous acetonitrile, the product is N,N'-bis(2-propenyl)-2,7-diazapyrenium diperchlorate or dichloride depending on whether the DDQ oxidation is followed by addition of concd HClO(4) or concd HCl, respectively. Importantly, if the DDQ oxidation is quenched with HBr, Br(-) is oxidized to Br(2) by unreacted DDQ, and the resulting product is N, N'-bis(2,3-dibromopropyl)-2,7-diazapyrenium dibromide. Comparative absorption and time-resolved emission studies provide evidence for possible dimerization of N,N'-bis(2-propenyl)-2,7-diazapyrenium diperchlorate in CH(3)CN.     

An Improved and Efficient Preparation of the Chiral NAD(P)H Model (S_s)-1-Benzy1-3-(p-tolylsulfinyl)-1,4-dihydropyridine

Chiral NAD(P)H models are important reduction reagents in asymmetric synthesis. (S,)l-Benzyl-3-(p-tolylsulfinyl)-1,4 1 is one of these models, which canreduce carbonyl and unsaturated compound under mild conditions with highenantioselectivity'. An impressive example is that methyl benzoylformate is reduced byl in the presence of Mg= or Zn' to methyl (R)-mandelate with up to 97% e.e. at roomtemperature'. Our investigation' has shown that the reduction of allylic bromide by Iwithout Mg:* o…