Catalytic asymmetric coupling of 2-naphthols by chiral tridentate oxovanadium (IV) complexes

A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted and N-3,4-benzo- and N-5,6-benzo-salicylidene-alpha-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O(2). The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-1-naphthaldehyde and valine (or phenylalanine) in CCl(4), leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.     

Catalytic Asymmetric Coupling of 2-Naphthols by Chiral Tridentate Oxovanadium(IV) Complexes

A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted-, N-3,4-benzo-and N-5,6-benzo-salicylidene-α-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O2. The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-l-naphthaldehyde and valine (or phenylalanine) in CCl4, leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.     

Enantioselective oxidative biaryl coupling reactions catalyzed by 1,5-diazadecalin metal complexes: efficient formation of chiral functionalized BINOL derivatives

Chiral 1,5-diaza-cis-decalins have been examined as ligands in the enantioselective oxidative biaryl coupling of substituted 2-naphthol derivatives. Under the optimal conditions employing 2.5-10 mol % of a 1,5-diaza-cis-decalin copper(II) catalyst with oxygen as the oxidant, enantioselective couplings (44-96% ee) could be achieved for a range of 3-substituted 2-naphthols including the ester, ketone, phosphonyl, and sulfonyl derivatives. The relationship between the substitution of the naphthalene starting materials and reactivity/selectivity is determined by several factors which act in concert: (1) the effect of substituents on the oxidation potential of the substrate, (2) the ability of the substrate to participate in a chelated copper complex which depends on (a) the inherent coordinating ability of the 3-substituent and (b) substituent steric interactions that affect chelation between the 2-hydroxyl and 3-substituent, (3) the effect of substituents on dissociation of the product from the copper catalyst.     

Vanadium-catalyzed sulfenylation of indoles and 2-naphthols with thiols under molecular oxygen

Vanadium oxyacetylacetonate [VO(acac)(2)] works as a catalyst for the direct synthesis of 3-sulfanylindoles from indoles and thiols under an atmospheric pressure of molecular oxygen as a reoxidant. For example, the reaction of 2-phenylindole with benzenethiol in the presence of a catalytic amount of VO(acac)(2), potassium iodide, and 2,6-di-tert-butyl-p-cresol in chlorobenzene under molecular oxygen proceeds to afford 2-phenyl-3-(phenylsulfanyl)indole in 86% yield. This catalytic system can also be applied to 2-naphthols instead of indoles to give the corresponding 1-sulfanyl-2-naphthols in up to 57% yield.     

Synthesis of Chiral Propargylamines,Chiral 1,2-Dihydronaphtho[2,1-b]furans and Naphtho[2,1-b]furans with C-Alkynyl N,N′-di-(tert-butoxycarbonyl)-aminals and β-Naphthols

Chiral phosphoric acid-catalyzed couplings of C-alkynyl N,N′-di-(tert-butoxycarbonyl)-aminals with β-naphthols led to chiral propargylamines in moderate to high yields with high to excellent enantioselectivity, in which the reactions underwent sequential chiral phosphoric acid-catalyzed in situ formation of N-(tert-butoxycarbonyl)-imines (N-Boc-imines) from the aminals, and 1,2-addition of β-naphthols to the N-Boc-imines. Chiral 1,2-dihydronaphtho[2,1-b]furans and naphtho[2,1-b]furans were prepared with satisfactory results when 10 mol% AgOAc and 20 mol% 2,6-lutidine or 1.2 equiv. of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were added to the resulting chiral propargylamines solution, respectively.     

Synthesis of polysubstituted-2-naphthols

Substituted 3-(triisopropylsilyl)-2-naphthols are prepared by an aluminum chloride catalyzed condensation of phenyl acetyl chloride derivatives and triisopropylsilyl acetylene. The yields obtained are in the range of 41% to 67%. The reaction is regiospecific and gives only the 3-(trialkylsilyl)-2-naphthol isomer.     

Unexpected results of a SNAr-reaction. A novel synthetic approach to 1-arylthio-2-naphthols

1-(Phenylthio)-3-(pyridin-3-yl)-2-naphthol was obtained as an unexpected result of a nucleophilic aromatic substitution reaction of 3-(pyridine-3-yl)naphthalene-2-yl trifluoromethanesulfonate with thiophenol. This observation led to the discovery of an easy to handle method to synthesize 1-arylthio-2-naphthols. It has been revealed that electron withdrawing groups on the aryl thiol promoted the yields and heterocycle substituents at the 3-position of the naphthalene core are tolerable by the reaction. This reaction can thus serve as a corner stone in the structural diversification of 3-heterocycle substituted 1-arylthio-2-naphthols as potential inhibitors of cytochrome P450.     

The rational design of novel chiral oxovanadium(IV) complexes for highly enantioselective oxidative coupling of 2-naphthols

Several novel chiral oxovanadium(IV) complexes have been designed and prepared for the asymmetric catalytic oxidative coupling of 2-naphthols with high enantioselectivities of 83-98% ee.     

Synthesis,structure, and growth-promoting activity of 1-alkyl-4-(3-naphthyloxyprop-1-ynyl)piperidin-4-ols

Alkylation of 1- and 2-naphthols with propargyl bromide in acetone in the presence of potassium carbonate led to prop-2-ynyloxynaphthalenes, which upon reaction with 1-alkyl-piperidin-4-ones under the Favorsky conditions afforded the corresponding tertiary alcohols. 1-Methyl-4-[3-(2-naphthyloxy)prop-1-ynyl]piperidin-4-ol hydrochloride was found to possess a high growth-promoting activity in the concentration of 0.001% upon the pre-sowing treatment of beetroot seeds and potatoes and increase their productivity by ～20%.     

Dinuclear chiral vanadium catalysts for oxidative coupling of 2-naphthols via a dual activation mechanism

This review describes our recent efforts in the development of chiral dinuclear vanadium complexes that work as dual activation catalysts for the oxidative coupling of 2-naphthols. The dinuclear vanadium(iv) complex (R(a),S,S)- was prepared by complexation of VOSO(4) with the Schiff base derived from (R)-3,3'-diformyl-2,2'-dihydroxy-1,1'-binaphthyl () and (S)-tert-leucine. Since the dinuclear vanadium(iv) complex was found to be readily oxidized to afford a corresponding vanadium(v) species during preparation in air, a new synthetic procedure using VOCl(3) has been applied towards dinuclear vanadium(v) complexes (R(a),S,S)- and (R(a),S,S)-. To the best of our knowledge, (R(a),S,S)-, and show considerably higher catalytic activity than previously reported vanadium complexes for the oxidative coupling of 2-naphthols.     

Sulfonated 1-(2-pyridylazo)-2-naphthols and 2-(2-pyridylazo)-1-naphthols as spectrophotometric reagents: Determination of nickel

Three sulfonated 1-(2-pyridylazo)-2-naphthols and six sulfonated 2-(2-pyridylazo)-1-naphthols were synthesized, and their application to the spectrophotometric determination of metals was studied. The acidity constants of the reagents and the stability constants of the nickel chelates are reported, and the relationship between their properties and the position of the sulfonic acid group is discussed. 1-(2-Pyridylazo)-2-naphthol-6-sulfonic acid (PAN-6S) and 1-(2-pyridylazo)-2-naphthol-7-sulfonic acid (PAN-7S) are sensitive and selective reagents for nickel. The determination of nickel in the presence of cobalt with PAN-6S is described. Extraction of the chelate as the ion-pair with tetraphenylarsonium ions into chloroform is suitable for the determination of 1–10 μg Ni at 570 nm; the molar absorptivity is 56 000 l mol^-1 cm^-1, and interferences are easily avoided.     

Phosphonylation of 1,3-Diaryl-2,3-dihydro1H-naphth[1,2-e][1,3]oxazine by Dialkyl and Diaryl Phosphonates

The possibility of using of easily available 1-(α-aminobenzyl)-2-naphthols as chiral auxiliaries in the synthesis of non-racemic α-aminophosphonates has been shown.     

Pd-catalyzed ring opening of oxa- and azabicyclic alkenes with aryl and vinyl halides: efficient entry to 2-substituted 1,2-dihydro-1-naphthols and 2-substituted 1-naphthols

An efficient syntheses of 2-substituted 1,2-dihydro-1-naphthols and 2-substituted 1-naphthols has been developed that involves the sequential palladium-catalyzed ring opening of oxabicyclic alkenes with aryl and vinyl halides followed by oxidation of with IBX. In the first step of the sequence, a combination of Pd(OAc)2, PPh3, Zn, and PMP in dry DMF was employed to catalyze the ring opening of 7-oxabenzonorbornadienes with aryl and vinyl halides to afford the corresponding cis-2-substituted 1,2-dihydronaphthols in good to excellent yields. These reactions occurred under very mild conditions with a variety of aryl halides bearing electron-withdrawing or -donating groups. Similarly, a 7-azabenzonorbornadiene substituted with an electron-withdrawing group on the nitrogen atom underwent facile ring-opening reaction with aryl halides to provide cis-2-substituted (1,2-dihydro-1-naphthyl)carbamates in excellent yields. Oxidation of the intermediate 1,2-dihydro-1-naphthols using IBX yielded the corresponding 2-substituted 1-naphthols in good to excellent yields.     

Ruthenium-catalyzed cyclization of epoxide with a tethered alkyne: formation of ketene intermediates via oxygen transfer from epoxides to terminal alkynes

Treatment of (o-ethynyl)phenyl epoxides with TpRuPPh(3)(CH(3)CN)(2)PF(6) (10 mol %) in hot toluene (100 degrees C, 3-6 h) gave 2-naphthols or 1-alkylidene-2-indanones very selectively with isolated yields exceeding 72%, depending on the nature of the epoxide substituents. Surprisingly, the reaction intermediate proved to be a ruthenium-pi-ketene species that can be trapped efficiently by alcohol to give an ester compound. This phenomenon indicates a novel oxygen transfer from epoxide to its terminal alkyne catalyzed by a ruthenium complex. A plausible mechanism is proposed on the basis of reaction products and the deuterium-labeling experiment. The 2-naphthol products are thought to derive from 6-endo-dig cyclization of (o-alkenyl)phenyl ketene intermediates, whereas 1-alkylidene-2-indanones are given from the 5-endo-dig cyclization pathway.     

A simple,convenient preparation for enantiomerically pure 1,1′-bi-2-naphthols

A new preparative method for enantiomerically pure 1,1′-bi-2-naphthols is described. 1,1′-Bi-2-naphtholboric anhydride generated from the reaction of racemic 1,1′-bi-2-naphthol and boric acid in toluene is reacted with (S)-proline to produce 1,1′-bi-2-naphtholboric proline anhydride. Its two diastereomers were efficiently separated in THF. After treating successively with NaOH, HCl, and recrystallizing from benzene, enantiomerically pure (S)- and (R)-1,1′-bi-2-naphthol were obtained in 71–79% yield and in 62–74% yield, respectively.     

Nitromethyl benzoate annulation reactions: a rapid construction of the stealthin skeleton

The annulation of 2-(nitromethyl)benzoates with enones gave 4-nitro-1-naphthols in good yields. The carbocyclic framework of the stealthins was synthesized.     

Reactions of N-Arylsulfonyl-2-arenesulfonamido-1,4-benzo-quinone 4-Imines with Naphthols

Reactions of N-arylsulfonyl-2-arenesulfonamido-1'4-benzoquinone 4-imines unsubstituted in thering or 6-chloro, 5'6-dichlorosubstituted with 1- or 2-naphthols, 2-methoxynaphthalene provided thecorresponding N-arylsulfonyl-2-arenesulfonamido-6-[2-hydroxy(methoxy)-1-naphthyl]-4-aminophenols fromthe unsubstituted reagent and reduction products from the mono- and dichlorosubstituted quinone imines.     

Bi(OTf)3-catalyzed tandem reaction of naphthols with β,γ-unsaturated a-ketoesters.Efficient synthesis of functionalized 4H-chromenes

An efficient synthesis of functionalized 4H-chromenes by the tandem reaction of b,g-unsaturated aketoesters with 2-naphthols,1-naphthols,and 1,3-dihydroxynaphthalenes has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3,5 mol%] under mild conditions.The functionalized 4H-chromene synthesis and our previous 2Hchromene hemiacetal synthesis could complement each other to enrich reaction diversity.     

Facile synthesis of 1-(arylimino)naphthalen-2(1H)-ones from anilines and 2-naphthols promoted by NaBr/K2S2O8/CAN

An efficient method has been developed for the synthesis of 1-(arylimino)naphthalen-2(1H)-ones through the cascade reaction of anilines and 2-naphthols promoted by NaBr/K₂S₂O₈/Ce(NH₄)₂(NO₃)₆. Using this protocol, a series of 1-(arylimino)naphthalen-2(1H)-ones was obtained in good to excellent yields (17 examples, 70–92% yields). The reactions may proceed through the following steps: bromination of 2-naphthols by in-situ-generated bromine from NaBr and K₂S₂O₈ to afford 1-bromonaphthalen-2-ols, coupling of 1-bromonaphthalen-2-ols with anilines to afford the corresponding amines, and subsequent oxidation of the amines into the products by Ce(NH₄)₂(NO₃)_6. These newly obtained α-imine ketones have great potentials for synthesis of special optical materials bearing naphthalene moiety.     

Studies on the chemistry of 2-(2-oxo-3-phenylpropyl)-benzaldehydes: novel total synthesis of 3-phenylnaphthalen-2-ols and 2-hydroxy-3-phenyl-1,4-naphthoquinones

We describe the first studies on the chemistry of 2-(2-oxo-3-phenylpropyl)benzaldehydes, which were converted into 3-benzylisochromen-1-ones via the corresponding 2-(2-oxo-3-phenylpropyl)benzoic acid. The 2-(2-oxo-3-phenylpropyl)benzaldehydes proved to be convenient starting materials for the synthesis of 3-phenyl-2-naphthols. Oxidation of the latter compounds resulted in a novel, efficient synthesis of 3-phenyl-1,2-naphthoquinones, which were efficiently transformed into 2-hydroxy-3-phenyl-1,4-naphthoquinones.