An Efficient Synthesis of 14‐Aryl or Alkyl‐14H‐Dibenzo[a. j]Xanthenes Using Reusable HBF4‐SiO2 Catalyst Under Thermal and Solvent‐Free Conditions

A simple and convenient procedure for the synthesis of 14‐aryl or alkyl‐14H‐dibenzo[a. j]xanthene derivatives is described through a one‐pot condensation of β‐naphthol with various aryl or alkyl aldehydes in the presence of HBF₄‐SiO₂ as the catalyst under thermal and solvent‐free conditions.     

Perchloric Acid–Silica (HClO4⋅SiO2)‐Catalyzed Synthesis of 14‐Alkyl‐ or 14‐Aryl‐14H‐dibenzo[a,j]xanthenes and N‐[(2‐Hydroxynaphthalen‐1‐yl)methyl]amides

The synthesis of 14‐aryl‐ or 14‐alkyl‐14H‐dibenzo[a,j]xanthenes 3 involving the treatment of naphthalen‐2‐ol ( 1 ) with arenecarboxaldehydes or alkanals 2 in the presence of HClO₄?SiO₂ as a heterogeneous catalyst was achieved (Table 1), and this reaction was extended to the preparation of N‐[(2‐hydroxynaphthalen‐1‐yl)methyl]amides 5 by a three‐component reaction with urea ( 4a ) or an amide 4b – d as a third reactant (Table 2).     

Convenient Synthesis of 14‐Aryl‐14‐H‐dibenzo[a,j]xanthenes Catalyzed by Acyclic Brønsted Acidic Ionic Liquid [H—NMP]+[HSO4]− under Microwave Irradiation

Efficient method for direct preparation of 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes through condensation of β‐naphthol with various aromatic aldehydes in the presence of the catalytic amount of [H—NMP]⁺[HSO₄]^? under microwave irradiation was described. This method has the advantages such as; very easy reaction workup, absolute separation of catalyst from the reaction mixture and smooth recyclability of catalyst. In this reaction 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes were obtained as desired products in excellent yields and short reaction times via green and one‐pot procedure.     

Silica Gel‐Supported Polyphosphoric Acid (PPA/SiO2): An Efficient and Reusable Heterogeneous Catalyst for Facile Synthesis of 14‐Aryl‐14H‐dibenzo[a,j]xanthenes under Solvent‐free Conditions

A simple, efficient and green method for the synthesis of 14‐aryl‐14H‐dibenzo[a,j]xanthenes by a one‐pot condensation reaction of β‐naphthol and aryl aldehydes using silica gel‐supported polyphosphoric acid (PPA/SiO₂), an effective and reusable catalyst, under solvent‐free conditions is described. The present methodology offers several advantages, such as a simple procedure with an easy work‐up, short reaction times, high yields, and the absence of any volatile and hazardous organic solvents.     

Iron‐Catalyzed anti‐Selective Carbosilylation of Internal Alkynes

Reported is the anti ‐selective carbosilylation of internal alkynes with silylborane and alkyl halides using a FeBr₂/DPPE catalyst system. The iron catalyst allows simultaneous introduction of a carbon electrophile and a silicon nucleophile to simple internal alkynes, including diaryl‐, dialkyl‐, and aryl/alkyl‐substituted alkynes, in a highly stereoselective manner. Alkyl halides are applicable as the electrophiles, thereby enabling the synthesis of a variety of tetrasubstituted alkenylsilanes. In addition, syn ‐selective carbosilylation was achieved through stereoswitching, by using a silylborane having oxygen functionality on the silyl group. This novel iron‐catalyzed carbosilylation is a useful tool for expedient synthesis of stereodefined multisubstituted olefins, a fundamental structural motif in organic chemistry.     

Study of direction of cyclization of 1‐azolil‐4‐aryl/alkyl‐thiosemicarbazides

On a four series of 1‐azolil‐4‐aryl/alkyl‐thiosemicabazides, a study on the influence of azole moiety on the capability for intramolecular cyclization and its direction was carried out. It was found that for 4‐aryl/alkyl‐thiosemicabazides with triazole, imidazole, or pyrrole moiety at N‐1 nitrogen atom possible products were only s‐triazoles, both in alkaline and acidic medium. Successful dehydrocyclization of 1‐azolil‐4‐aryl/alkyl‐thiosemicarbazides leading to a thiadiazole has been documented only for a series of 1‐(4‐methyl‐1,2,3‐thiadiazol‐5‐yl‐carbonyl)‐4‐aryl/alkyl‐thiosemicarbazides. It can be speculative that the determination of pK_a value of oxygen atom of 1‐azolil‐4‐aryl/alkyl‐thiosemicarbazide can be a very valuable parameter in the prediction of the possibility of dehydrocyclization to form thiadiazole. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:521–532, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20643     

Facile Catalyzed Preparation of 14‐Aryl‐ or Alkyl‐14‐H‐dibenzo[a,j]xanthenes by Dodecylphosphonic Acid and Dodecylsulfamic Acid: Environmentally Benign Methods

Under mild‐ and solvent‐free conditions, one‐pot preparation of 14‐alkyl‐ or 14‐aryl‐14‐H‐dibenzo[a,j]xanthenes could proceed in the presence of catalytic amounts of dodecylphosphonic acid (DPA) and dodecylsulfamic acid (DSA) in good to excellent yields. In these reactions, DPA and DSA are recovered by straightforward work‐ups.     

Ketones from Nickel‐Catalyzed Decarboxylative,Non‐Symmetric Cross‐Electrophile Coupling of Carboxylic Acid Esters

Synthesis of the C?C bonds of ketones relies upon one high‐availability reagent (carboxylic acids) and one low‐availability reagent (organometallic reagents or alkyl iodides). We demonstrate here a ketone synthesis that couples two different carboxylic acid esters, N‐hydroxyphthalimide esters and S‐2‐pyridyl thioesters, to form aryl alkyl and dialkyl ketones in high yields. The keys to this approach are the use of a nickel catalyst with an electron‐poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl₂ to enhance the reactivity of the NHP ester. The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with α‐heteroatoms. The conditions can be employed in the coupling of complex fragments, including a 20‐mer peptide fragment analog of Exendin(9–39) on solid support.     

New Pyrazolyl‐Nicotinic Acids,Methyl Esters,and 1,3,4‐Oxadiazolyl‐pyrazolyl‐pyridine Tricyclic Scaffold Derivatives from 6‐Hydrazinylnicotinic Acid Hydrazide Hydrate

This paper describes an efficient approach for the synthesis of a new series of 6‐[3‐alkyl(aryl/heteroaryl)‐5‐trifluoromethyl‐1H‐pyrazol‐1‐yl]nicotinic acids (where alkyl = CH₃; aryl = Ph, 4‐OCH₃Ph, 4,4′‐BiPh; and heteroaryl = 2‐Furyl) from the hydrolysis reaction of alkyl(aryl/heteroaryl)substituted 2‐(5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1H‐pyrazol‐1‐yl)‐5‐(5‐trifluoromethyl‐5‐hydroxy‐4,5‐dihydro‐1H‐1‐carbonylpyrazol‐1‐yl)pyridines, under basic conditions and at 70–95% yields. In a subsequent step, the esterification reaction of pyrazolyl‐nicotinic acids done in thionyl chloride and methanol led to the isolation of a series of methyl 6‐[alkyl(aryl/heteroaryl)‐5‐trifluoromethyl‐1H‐pyrazol‐1‐yl] nicotinates as stable hydrochloride salts at 64–84% yields, which could be easily converted to hydrazides to give new oxadiazolyl‐pyrazolyl‐pyridine tricyclic scaffolds at good yields from a [4 + 1] cyclocondensation reaction with 1,1,1‐triethoxyethane and 1‐(triethoxymethyl)benzene as the reagent/solvent.     

Ketones from Nickel‐Catalyzed Decarboxylative,Non‐Symmetric Cross‐Electrophile Coupling of Carboxylic Acid Esters

Synthesis of the C?C bonds of ketones relies upon one high‐availability reagent (carboxylic acids) and one low‐availability reagent (organometallic reagents or alkyl iodides). We demonstrate here a ketone synthesis that couples two different carboxylic acid esters, N‐hydroxyphthalimide esters and S‐2‐pyridyl thioesters, to form aryl alkyl and dialkyl ketones in high yields. The keys to this approach are the use of a nickel catalyst with an electron‐poor bipyridine or terpyridine ligand, a THF/DMA mixed solvent system, and ZnCl₂ to enhance the reactivity of the NHP ester. The resulting reaction can be used to form ketones that have previously been difficult to access, such as hindered tertiary/tertiary ketones with strained rings and ketones with α‐heteroatoms. The conditions can be employed in the coupling of complex fragments, including a 20‐mer peptide fragment analog of Exendin(9–39) on solid support.     

Regioselective synthesis of 1,4‐disubstituted triazoles using bis[(L)prolinato‐N,O]Zn complex as an efficient catalyst in water as a sole solvent

A concise, convenient and mild route for one‐pot regioselective synthesis of N‐aryl‐ and N‐alkyltriazoles in water as a sole solvent is reported. The methodology involves a three‐component reaction comprising aryl/alkyl‐alkyne, sodium azide and aryl/alkyl/allyl halide catalyzed by zinc(II) L ‐prolinate. Prominent features of our protocol are incorporation of transition metal catalyst other than copper, water as the reaction medium, recyclability of catalyst and avoidance of hazardous aryl azide as a reactant. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis of 14‐{[(Un)substituted phenyl] or alkyl}‐14H‐dibenzo[a,j]xanthenes Using Yb(OTf)3 as an Efficient Catalyst under Solvent‐free Conditions

A series of 14‐{[(Un)substituted phenyl] or alkyl}‐14H‐dibenzo[a,j]xanthenes were prepared under solvent‐free conditions by Yb(OTf)₃ catalyzed condensation reactions of β‐naphthol with various aldehydes. The process presented here is operationally simple, environmentally benign and has good to excellent yields. Furthermore, the catalyst can be recovered conveniently and reused efficiently.     

Pinacol Rearrangement of 3,4‐Dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones: An Alternative Pathway to Viridicatin Alkaloids and Their Analogs

3‐Alkyl/aryl‐3‐hydroxyquinoline‐2,4‐diones were reduced with NaBH₄ to give cis‐3‐alkyl/aryl‐3,4‐dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H₂SO₄, resulting in 4‐alkyl/aryl‐3‐hydroxyquinolin‐2(1H)‐ones. When a benzyl (Bn) group was present in position 3 of the starting compound, its elimination occurred during the rearrangement, and the corresponding 3‐hydroxyquinolin‐2(1H)‐one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, ¹H‐ and ¹³C‐NMR spectroscopy, as well as mass spectrometry.     

Gold‐Catalyzed Intramolecular [3+2] Cycloadditions of 1‐Aryl‐1‐allene‐6‐enes

Treatment of 1‐aryl‐1‐allen‐6‐enes with [PPh₃AuCl]/AgSbF₆ (5 mol %) in CH₂Cl₂ at 25 °C led to intramolecular [3+2] cycloadditions, giving cis‐fused dihydrobenzo[a]fluorene products efficiently and selectively. The reactions proceeded with initial formation of trans/cis mixtures of 2‐alkyl‐1‐isopropyl‐2‐phenyl‐1,2‐dihydronaphthalene cations B, which were convertible into the desired cis‐fused cycloadducts through the combined action of a gold catalyst and a Brønsted acid. Theoretic calculation supports the participation of the trans‐B cation as reaction intermediate. Although HOTf showed similar activity towards several 1‐aryl‐1‐allen‐6‐enes, it lacks generality for this cycloaddition reaction.     

New Approaches to the Synthesis of 4‐(2‐Aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones and 3‐Ureidoindoles and a Study of Their Interconversion

3‐Alkyl/aryl‐3‐ureido‐1H,3H‐quinoline‐2,4‐diones ( 2 ) and 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) react in boiling concentrated HCl to give 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ). The same compounds were prepared by the same procedure from 2‐alkyl/aryl‐3‐ureido‐1H‐indoles ( 4 ), which were obtained from the reaction of 3‐alkyl/aryl‐3‐aminoquinoline‐2,4(1H,3H)‐diones ( 1 ) with 1,3‐diphenylurea or by the transformation of 3a‐alkyl/aryl‐9b‐hydroxy‐3,3a,5,9b‐tetrahydro‐1H‐imidazo[4,5‐c]quinoline‐2,4‐diones ( 3 ) and 5‐alkyl/aryl‐4‐(2‐aminophenyl)‐1,3‐dihydro‐2H‐imidazol‐2‐ones ( 6 ) in boiling AcOH. The latter were converted into 1,3‐bis[2‐(2‐oxo‐2,3‐dihydro‐1H‐imidazol‐4‐yl)phenyl]ureas ( 5 ) by treatment with triphosgene. All compounds were characterized by ¹H‐ and ¹³C‐NMR and IR spectroscopy, as well as atmospheric pressure chemical‐ionisation mass spectra.     

Indium triflate‐catalyzed one‐pot synthesis of 14‐alkyl or aryl‐14H‐dibenzo[a,j]xanthenes in water

A mild, efficient, and environment friendly method has been developed for the synthesis of 14‐alkyl or aryl‐14H‐dibenzo[a, j]xanthenes by condensation of 2‐naphthol and aldehydes in the presence of a catalytic amount of indium(III) triflate (2 mol%) in water at 100°C. Different types of aromatic and aliphatic aldehydes are used in the reaction, and in all cases the products synthesized in moderate to excellent yields. © 2009 Wiley Periodicals, Inc. Heteroatom Chem 20:232–234, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20539     

A rhodium‐catalyzed route for oxidative coupling and cyclization of 2‐aminobenzyl alcohol with ketones leading to quinolines

2‐Aminobenzyl alcohol undergoes oxidative cyclization with aryl(alkyl), alkyl(alkyl) and cyclic ketones in dioxane at 80° in the presence of a catalytic amount of RhCl(PPh₃)₃ along with KOH to afford the corresponding quinolines in good yields. The catalytic pathway seems to be proceeded via a sequence involving initial oxidation of 2‐aminobenzyl alcohol to 2‐aminobenzaldehyde by a rhodium catalyst, cross aldol reaction between 2‐aminobenzaldehyde and ketones, and cyclodehydration.     

Regiospecific synthesis of trichloromethyl substituted 4,5‐dihydro‐1h‐1‐tosylpyrazoles

The regiospecific synthesis of a new series of eight 3‐alkyl(aryl)‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐1‐tosylpyrazoles is reported. The 1‐p‐tosyl‐2‐pyrazolines were obtained from the cyclocondensation reaction of 4‐alkyl(aryl)‐4‐alkoxy‐1,1,1‐trichloroalk‐3‐en‐2‐ones, [where alkyl = H, Me and aryl = ‐C₆H₅, 4‐CH₃C₆H₄, 4‐OCH₃C₆H₄, 4‐FC₆H₄, 4‐ClC₆H₄, 4‐BrC₆H₄,] with p‐tosylhydrazine in 64 to 92 % yields, employing anhydrous toluene at reflux or diethyl ether at room temperature as the reaction condition.     

Copper‐Catalyzed N‐Arylation of Polysubstituted Pyridines Synthesized by the Novel Reaction of N‐Sulfonyl Ketenimine and Malononitrile‐Trichloroacetonitrile Adduct

In this study, we synthesized some new derivatives of N‐(4‐amino‐5‐cyano‐6‐(trichloromethyl)pyridin‐2‐yl)alkyl sulfonamides in the presence of a copper catalyst. A one‐pot reaction system was used, and four components participated in the process. These four components were sulfonyl azides, terminal alkynes, malononitrile, and trichloroacetonitrile. The reaction rate was increased by the use of copper (I) iodide as the catalyst and tetrahydrofuran was used as the solvent. We achieved the final compounds in moderate to good yields. Moreover, we converted “NH₂” side group to N‐aryl by the use of various aryl halide analogs in acetonitrile as the solvent, under mild reaction and at the room temperature.     

BTADCI Promoted One‐pot Synthesis of 14‐aryl‐14H‐dibenzo [a,j] Xanthenes

A convenient eco‐friendly one‐pot synthesis of 14‐aryl‐14H‐dibenzo [a, j] xanthenes were developed by the condensation of aromatic aldehydes and β‐naphthol with BTADCI (Benzyltrimethylammonium dichloroiodate) as catalyst under solvent free conditions and microwave irradiation with much more rate accelerations and afford very good yields. Developed protocols involve mild reaction conditions, simple isolation of derivatives with inexpensive reagents.