Efficient Regioselective Synthesis Research Articles

ChemInform Abstract: An Efficient Regioselective Synthesis of Functionalized Biphenyls via Sequential Reactions of Aromatic Aldehydes and β‐Keto Esters or Ketones.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Iodobenzene Diacetate Mediated Oxidation of N-Substituted Hydrazones of Chalcones: An Efficient Regioselective Synthesis of 1,3,5-Trisubstituted Pyrazoles

Iodobenzene diacetate, a relatively benign nonmetallic oxidant, has been utilized efficiently for the oxidation of N-substituted hydrazones of chalcones to afford 1,3,5-trisubstituted pyrazoles under mild reaction conditions.

An efficient regioselective synthesis of functionalized biphenyls via sequential reactions of aromatic aldehydes and β-keto esters or ketones

Knoevenagel/Michael/Aldol reactions of aromatic aldehydes and β-keto esters/ketones in a sequential manner yielded intermediate cyclohexanones in good yields. The latter, on oxidative aromatization with iodine, afforded functionalized biphenyls with at least one phenolic hydroxyl in moderate to good yields.

ChemInform Abstract: Efficient Regioselective Synthesis of 4‐ and 5‐Substituted Isoxazoles under Thermal and Microwave Conditions.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Efficient regioselective synthesis of 4‐ and 5‐substituted isoxazoles under thermal and microwave conditions

Abstractmagnified imageThe [2+3] cycloaddition reaction between nitrile oxides 2 and the captodative olefins 1 or the methyl crotonate derivatives 4 is regioselective and leads to the formation of the 5‐substituted amino‐isoxazole 3 or the 4‐substituted methoxycarbonyl‐isoxazole 5 derivatives, respectively. All these reactions are greatly accelerated by microwave irradiation without changing their regioselectivity with respect to the thermal conditions.

ChemInform Abstract: A Highly Efficient Regioselective One‐Pot Synthesis of 2,3,6‐Trisubstituted Pyridines and 2,7,7‐Trisubstituted Tetrahydroquinolin‐5‐ones Using K5CoW12O40×3H2O as a Heterogeneous Recyclable Catalyst.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A substituent directed regioselective synthesis of aryl/pyronyl pendant unusual adipate and tetrahydronaphthalene

An efficient regioselective synthesis of pyronyl pendant ethyl methylthiocarbonylalkanoates 5 has been delineated from the base catalyzed reaction of suitably functionalized 2-pyranone 1 and 2-carbethoxycycloalkanones 2, 6 through successive substitution and regioselective ring opening by in situ generated mercaptide ion. To assess the effect of C-4 substituent on regioselectivity, reactions of 6-aryl-3-cyano-4-(piperidin-1-yl)-2-oxopyran 8 with 2-carbethoxycyclohexanone 6a and 2-carbethoxy-2-methylcyclohexanone 6b were carried out separately under analogous reaction conditions but the compounds isolated were identical and characterized as 4-aryl-8-methyl-2-piperidin-1-yl-5,6,7,8-tetrahydronaphthalene-1-carbonitriles 9. Ethyl 2-(5-amino-4′-bromo-4,6-dicyanobiphenyl-3-yl)-5-methylsulfanylcarbonylpentanoate 10 has also been prepared through base catalyzed ring transformation of ethyl 2-[6-(4-bromophenyl)-3-cyano-2-oxo-2 H-pyran-4-yl]-5-methylsulfanylcarbonylpentanoate 5d by malononitrile in DMF.

A Regioselective Approach to Trisubstituted 2 (or 6)-Arylaminopyrimidine-5-carbaldehydes and Their Application in the Synthesis of Structurally and Electronically Unique G∧C Base Precursors

An efficient regioselective synthesis of trisubstituted 2(or 6)-arylaminopyrimidine-5-carbaldehydes has been developed via an S(N)Ar reaction of 2,4,6-trichloropyrimidine-5-carbaldehyde with aniline, methylamine, and alkoxide nucleophiles using a combination of phase-transfer catalysis and more traditional SNAr reaction conditions. We demonstrate that in a few synthetic steps, highly functionalized fused-bicyclic pyrimidine substrates can be accessed from the trisubstituted 2-arylaminopyrimidine-5-carbaldehydes. Furthermore, these fused-bicyclic compounds are readily derivatized using the Suzuki cross-coupling reaction to generate electronically and structurally unique GlambdaC base precursors.

Regioselective Synthesis of Novel Dispiro‐oxindoloindenoquinoxaline Pyrrolidines through 1,3‐Dipolar Cycloaddition Methodology

A facile and efficient regioselective synthesis of dispiroindenoquinoxaline pyrrolidine derivatives by a one‐pot four‐component 1,3‐dipolar cycloaddition reaction is delineated.

Facile Synthesis of Stop-Sign Ene

Cyclooctatetraenes (COTs) have found application in a variety of fields, materials science, catalysis, and bio-active products to name a few. Previous syntheses of COTs involved Ni(0)-catalyzed cyclization of acetylenes or simple terminal alkynes; however, despite improvements, high yields and regioselectivity have remained elusive. Wender et al. demonstrate an efficient regioselective synthesis of COTs that is tolerant of a variety of functional groups (nitriles, protected amines, etc.) and peripheral ring sizes. Further, control over [2+2+2+2] (2) and [2+2+2] (3) cycloadditions can be achieved through high catalyst loading or slow addition of diyne. These data support a mechanism of metallacycle dimerization.

A highly efficient regioselective one-pot synthesis of 2,3,6-trisubstituted pyridines and 2,7,7-trisubstituted tetrahydroquinolin-5-ones using K 5CoW 12O 40·3H 2O as a heterogeneous recyclable catalyst

A systematic investigation into the regioselective one-pot, three-component condensation of enaminones 1a– g, β-dicarbonyl compounds 2a– c, and ammonium acetate in the presence of a catalytic amount of K 5CoW 12O 40·3H 2O (0.01 equiv or 1.0 mol %) under solvent free conditions, as well as in refluxing isopropanol, has been reported. The reaction was highly efficient to produce 2,3,6-trisubstituted pyridines 3a– g, 4a– g, and novel 2,7,7-trisubstituted-5,6,7,8-tetrahydroquinoline-5-ones 5a– g in excellent yields. The present procedure offers advantages of short reaction time, simple work-up, and the catalyst exhibited remarkable reusable activity.

Synthesis of arylated highly congested indans using a domino sequence

A novel and efficient regioselective synthesis of various arylated highly congested 7-aryl-5-methylsulfanylindan-4-carbonitriles ( 3a– f), methyl 7-aryl-5-methylsulfanylindan-4-carboxylates ( 10a– e) and 7-aryl-5-methylsulfanylindan-4-carboxylic acids ( 11a– e) through base-catalyzed reaction of 6-aryl-4-methylsulfanyl-2-oxo-2 H-pyran-3-carbonitriles ( 1a– f) and methyl 6-aryl-4-methylsulfanyl-2-oxo-2 H-pyran-3-carboxylates ( 9a– e) by cyclopentanone ( 2) has been delineated. The synthetic potential of 2-pyranone was explored further to generate molecular diversity using 6-aryl-4- sec-amino-2-oxo-2 H-pyran-3-carbonitriles ( 7a– h), 5,6-diaryl-4-methylsulfanyl-2-oxo-2 H-pyran-3-carbonitriles ( 5a, b) and methyl 5,6-diaryl-4-methylsulfanyl-2-oxo-2 H-pyran-3-carboxylates ( 12a, b) as precursors for the ring transformation by cyclopentanone to assess the effects of substituents on the course of the reaction to obtain highly congested indans, 6,7-diaryl-5-methylsulfanylindan-4-carbonitriles ( 6a, b), 7-aryl-5-(piperidin-1-yl)indan-4-carbonitriles ( 8a– h) and methyl 6,7-diaryl-5-methylsulfanylindan-4-carboxylates ( 13a, b).

Synthesis of New Chiral 4,5,6,7-Tetrahydro[1,2,3]triazolo[1,5-a]pyrazines from α-Amino Acid Derivatives under Mild Conditions

A practical and efficient regioselective synthesis of several new chiral 4,5,6,7-tetrahydro[1,2,3]triazolo[1,5-a]pyrazines is described from α -amino acid derivatives following intramolecular 'click' reaction as the key step. The method obviates product -purification; to obtain the pure triazole products, only the solvent needs to be evaporated.

Efficient Phenanthrene, Helicene, and Azahelicene Syntheses.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Single-Isomer Tetrasubstituted Olefins from Regioselective and Stereospecific Palladium-Catalyzed Coupling of β-Chloro-α-iodo-α,β-unsaturated Esters

The efficient regioselective and stereospecific synthesis of tetrasubstituted olefins using a mild and convenient method is disclosed. 2-Alkynyl esters are selectively converted to E-beta-chloro-alpha-iodo-alpha,beta-unsaturated esters by exposure to Bu4NI in refluxing dichloroethane. These products are produced cleanly, regio- and stereoselectively, and in high yields. Single-isomer tetrasubstituted olefins bearing four different carbon substituents are then synthesized by sequential palladium-catalyzed coupling reactions. Selectivity results from reactivity differences in the intermediate substrates.

Efficient Phenanthrene, Helicene, and Azahelicene Syntheses

Homolytic aromatic substitution reactions are used for the efficient regioselective synthesis of helicenes, phenanthrenes, and azahelicenes. The use of halo and alkoxy substituents to control the stereochemical outcome of this approach and X-ray studies of the resulting helicenes are described (see structure; red O, gray C).

Synthesis and Antiviral Activities of 1,2,3-triazole Functionalized Thymidines: 1,3-dipolar Cycloaddition for Efficient Regioselective Diversity Generation

Efficient regioselective synthesis of nucleoside conjugates was achieved by cycloaddition reaction of azides and alkynes using sodium ascorbate/ CuSO4 system as a catalyst. These 16 novel thymidine analogues were obtained in excellent yields (75-100%), employing mild reaction conditions with a broad scope of structural modification. For the compounds tested, no specific antiviral effects could be witnessed against a broad range of viruses.

An Efficient Regioselective Synthesis of Endocrocin and Structural Related Natural Anthraquinones Starting from Emodin.

AbstractFor Abstract see ChemInform Abstract in Full Text.

An efficient regioselective synthesis of endocrocin and structural related natural anthraquinones starting from emodin

Endocrocin and related naturally occurring anthraquinone pigments like cinnalutein could be synthesized regioselectively via a Marschalk type reaction, starting from the natural hydroxy anthraquinone emodin. Furthermore, the new tri- O-methyl protected emodin-2-carbaldehyde may serve as a promising synthon for new bathochromically shifted, higher generation photodynamically active hypericin derivatives.

Regioselective Synthesis of 4‐ and 5‐Oxazole‐phosphine Oxides and ‐phosphonates from 2H‐Azirines and Acyl Chlorides.

AbstractFor Abstract see ChemInform Abstract in Full Text.