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.     

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.     

Methyltrioxorhenium-catalyzed aerobic oxidative coupling of 2-naphthols to binaphthols

A variety of 2-naphthols have been selectively oxidized to their corresponding 1,1′-bi-2-naphthols in excellent yields with molecular oxygen using methyltrioxorhenium as catalyst.     

Organocatalytic enantioselective Friedel-crafts reactions of 1-naphthols with aldimines

An organocatalytic enantioselective Friedel-Crafts reaction of 1-naphthols with aldimines has been developed. The method affords a direct access to chiral aminoarylnaphthols in good yields and with good to high enantioselectivities.     

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.     

Synthesis of naphthalenes and 2-naphthols by the electrophilic cyclization of alkynes

[reactions: see text] A wide variety of substituted naphthalenes are readily prepared regioselectively under mild reaction conditions by the 6-endo-dig electrophilic cyclization of appropriate arene-containing propargylic alcohols by ICl, I2, Br2, NBS, and PhSeBr. 3-Iodo-2-naphthols have also been prepared in excellent yields by the cyclization of analogous 1-aryl-3-alkyn-2-ones. This methodology readily accommodates various functional groups and has been successfully extended to the synthesis of substituted carbazoles and dibenzothiophenes.     

Eco-friendly and efficient multi-component method for preparation of 1-amidoalkyl-2-naphthols under solvent-free conditions by dodecylphosphonic acid (DPA)

An efficient and direct eco-friendly protocol for the preparation of 1-amidoalkyl-2-naphthols employing a multi-component, one-pot condensation reaction between β-naphthol, aromatic or aliphatic aldehydes and benzamide or acetamide in the presence of dodecylphosphonic acid under solvent-free conditions has been described.     

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.     

无溶剂条件下三聚氰胺-Br_3催化一锅法合成1-氨基烷基-2-萘酚(英文)

A facile and efficient method has been developed for the synthesis of 1-amidoalkyl-2-naphthols via the one-pot multi-component condensation of 2-naphthol with aromatic aldehydes and acetamide or thioacetamide in the presence of melamine-Br3 under solvent-free conditions. There are several advantages to this reaction, including high yields, short reaction time, and high catalytic efficiency.     

Friedel–Crafts alkylation of 2-naphthols with enamides and enethers induced by catalytic amount of triarylaminium salt

A novel and efficient regioselective Friedel–Crafts alkylation reaction of 2-naphthols with electron-rich enamides or enethers initiated by catalytic amounts of stable radical cation triarylaminium salt has been developed. The processes occur under mild conditions.     

A new synthesis of 2-fluoro-1-naphthols

A general synthesis of 2-fluoro-1-naphthols in two steps from 1-indanones is reported. The 1-indanones are first converted to difluoromethyl 2-fluoro-1-napthyl ethers by reaction with difluorocarbene source, trimethylsilyl 2-fluorosulfonyl-2,2-difluoroacetate (TFDA). These ethers are then converted in high yield to the respective naphthols by heating with a mixture of acetic acid and 48% HBr.     

无溶剂条件下离子液体[Hnmp]HSO4催化一锅法合成2 -氨基苯并噻唑-芳甲基-2-萘酚

以离子液体[Hnmp]HSO₄为催化剂, 在无溶剂条件下催化芳香醛、2-氨基苯并噻唑和2-萘酚合成一系列的2 -氨基苯并噻唑-芳甲基-2-萘酚. 该方法条件温和, 反应时间短, 产率高和对环境友好. 此外催化剂可以方便地回收, 且循环使用四次其催化活性并没有显著降低. 目标产物经过了¹H NMR, IR, MS和元素分析确证.     

Synthesis of 2-naphthols via carbonylative Stille coupling reaction of 2-bromobenzyl bromides with tributylallylstannane followed by the Heck reaction

A method for the synthesis of 2-naphthols 4 is described. The carbonylative Stille coupling reactions of 2-bromobenzyl bromides with tributylallylstannane to produce 2-bromobenzyl β,γ-unsaturated ketones 2 in satisfactory to excellent yields has been achieved. The isomerization of 2-bromobenzyl β,γ-unsaturated ketones 2 can readily occur under basic conditions to generate 2-bromobenzyl α,β-unsaturated ketones 3. The 2-bromobenzyl α,β-unsaturated ketones 3 can be transformed into 2-naphthols 4 via intramolecular Heck reaction in satisfactory to good yields.     

Al(HSO4)3: an efficient and heterogeneous reusable catalyst for the synthesis of 1-amidoalkyl-2-naphthols under thermal solvent-free conditions

An efficient green protocol for the synthesis of 1-amidoalkyl-2-naphthols using a three-component, one-pot condensation reaction of 2-naphthol, aromatic aldehyde and amides in the presence of Al(HSO₄)₃ as heterogeneous catalyst under thermal solvent-free conditions has been described. The present procedure offers advantages such as shorter reaction times, simple work-up procedure, excellent yields, recovery and reusability of catalyst.     

Nano Al2O3: an efficient and recyclable nanocatalyst for the one-pot preparation of 1-amidoalkyl-2-naphthols under solvent-free conditions

A direct approach for the one-pot preparation of 1-amidoalkyl-2-naphthols via three-component reaction of β-naphthol, aromatic aldehydes, and acetamide in the presence of nano-structured Al₂O₃ under solvent-free conditions has been developed. Some benefits of this procedure are: recyclability of the catalyst, short reaction time, high yield of the products, environmentally benign procedure, and facile work-up.

     

Efficient oxidative dimerization of 1-naphthols to 2,2-binaphthyls with dioxygen mediated by semiconductors

A novel and efficient oxidative dimerization of 1-naphthols 1 with dioxygen in the presence of several semiconductors including SnO₂, ZrO₂, and activated charcoal as catalytic mediators took place selectively to give the corresponding 2,2^′-binaphthols 2 or 2,2^′-binaphthyl-1,1^′-quinones 3 in excellent yields without light irradiation. Among these semiconductors, the catalytic activity of SnO₂ could be fully restored by appropriate reactivation treatment after oxidation. The products 2 and 3 should be useful as synthetic intermediates for natural binaphthyls.     

Rh-catalyzed [4 + 2] carbocyclization of vinylarylaldehydes with alkenes and alkynes leading to substituted tetralones and 1-naphthols

Regio-, diastereo-, and enantioselective intermolecular [4 + 2] carbocyclizations of vinylarylaldehydes with alkenes and alkynes leading to substituted tetralones and 1-naphthols have been developed by using a cationic rhodium(I)/dppb or dppp complex as a catalyst.     

Oxidative coupling of 2-substituted 1,2-dihydro-1-naphthols using Jones reagent: a simple entry into 3,3′-disubstituted 1,1′-binaphthyl-4,4′-diols

2-Substituted 1,2-dihydro-1-naphthols underwent regioselective oxidative dimerization, when treated with Jones reagent, to furnish 3,3′-disubstituted 1,1′-binaphthyl-4,4′-diols. A series of symmetrical binaphthols were prepared and it was shown that the coupling reaction proceeds via the sequential oxidation of 2-substituted 1,2-dihydro-1-naphthols to 2-substituted 1-naphthols, which oxidatively dehydrodimerized.     

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.     

取代1,1'-联-2-萘酚在铜胺络合物催化作用下的氧化反应

用CuCl2?2H2O与小分子的有机胺形成络合物,模拟氧化还原酶对多米诺式反应(Dominoreaction)进行催化反应,在氧气存在条件下,取代1,1'-联-2-萘酚化合物被氧化为二苯并呫吨类化合物,产物的结构经核磁共振、红外光谱及质谱进行确证.