Copper(II)‐Catalyzed Tandem Synthesis of Substituted 3‐Methyleneisoindolin‐1‐ones

An efficient strategy for the synthesis of a variety of 3‐methyleneisoindolin‐1‐ones has been developed. The reaction proceeded from coupling of 2‐iodobenzamides (or 2‐bromobenzamides) and terminal alkynes via Cu(OAc)₂·H₂O/2,2′‐biimidazole catalyzed in DMF at 60°C and subsequent additive cyclization produced substituted 3‐methyleneisoindolin‐1‐ones in good to excellent yields.     

Separation,interconversion, and insecticidal activity of the cis‐ and trans‐isomers of novel hydrazone derivatives

A series of cis‐ and trans‐isomers of hydrazone derivatives were separated and analyzed through HPLC with diode‐array detection and HPLC‐MS/MS using ESI and ion trap MS. Two single crystals (A‐5‐1 and C‐2‐1) of the trans‐isomers were obtained and determined using X‐ray crystallography data, and the cis‐ to trans‐isomerization under different conditions was discussed. Both of the cis‐ and trans‐isomers of A‐4 and A‐5 exhibited good insecticidal activities against Plutella xylostella.     

Efficient Prins cyclization in environmentally benign method using ion exchange resin catalyst

Abstract

Amberlyst-15^® (H⁺) resin catalyzes efficient one-pot solvent free Prins cyclization of an aldehyde and a homoallylic alcohol to yield dihydropyrans and 4-hydroxytetrahydropyrans. The products, which display interesting olfactory property, are obtained under mild condition and by simple work up. The recovered resin can be used repeatedly .     

Stereocontrolled Organocatalytic Strategy for the Synthesis of Optically Active 2,3‐Disubstituted cis‐2,3‐Dihydrobenzofurans

An intramolecular, organocatalyzed Michael addition has been developed to obtain biologically important 2,3‐disubstituted cis‐2,3‐dihydrobenzofurans. By using mandelic acid salts of primary aminocatalysts, derived from cinchona alkaloids, the intramolecular cyclization reaction has been developed to proceed in high yield, with moderate to good diastereoselectivity, and up to 99 % ee. Based on the absolute configuration of the formed 2,3‐disubstituted‐cis‐2,3‐dihydrobenzofurans and by considering the observed substrate scope restrictions, a mechanistic rationalization has been presented.     

Synthesis of 2,3‐Dihydro‐4H‐furo[3,2‐c] chromen‐4‐ones and 2,3‐Dihydronaphtho[2,3‐b]furan‐4,9‐diones by the Radical Cyclizations of Hydroxyenones with Electron-Rich Alkenes using Manganese(III) Acetate

We have obtained dihydrofurans 3a–j in the radical cyclization of 4‐hydroxycoumarin 1a and 2‐hydroxy‐1,4‐naphtoquinone 1b with electron rich alkenes 2a–i by manganese(III) acetate. Methods A and B, which have different molar ratios were studied comparatively in these reactions, and we observed that method B (molar ratio 2:1:3) gave the best results. Treatment of 4‐hydroxycoumarin 1a and electron rich alkenes 2a–e gave 2,3‐dihydro‐4H‐furo[3,2‐c]chromen‐4‐ones 3a–e in 36–86% yields by the method B. Under the same conditions, the reactions of 2‐hydroxy‐1,4‐naphtaquinone 1b with conjugated alkenes 2b and 2f–i afforded 2,3‐dihydronaphtho[2,3‐b]furan‐4,9‐diones 3f–j in an excellent yields.     

Synthesis of Some C‐3,4,5‐Substituted 2,6‐Dimethyl‐1,4‐dihydropyridines (4‐DHPs)

A series of C‐3,4,5‐substituted 2,6‐dimethyl‐1,4‐dihydropyridines (1,4‐DHPs) with pharmacological properties were prepared by a variation from the classical Hantzsch synthesis. The procedure involves treatment of the respective aldehyde with either ethyl‐3‐aminocrotonate or 3‐aminocrotonitrile in anhydrous acetic acid at temperatures not exceeding 60°C, thus minimizing by‐product formation. The structures of title compounds were elucidated by ¹H NMR, ¹³C NMR, FTIR, and elemental analysis.     

A NOVEL REDUCTIVE CYCLIZATION OF ARYLMETHYLIDENEMALONONITRILE PROMOTED BY LOW-VALENT TITANIUM

ABSTRACT

The intermolecular and intramolecular reductive coupling reactions of arylmethylidenemalononitriles induced by low-valent titanium have been studied. A possible reaction mechanism is proposed.     

New Cyclization Route to the Skeletons of Lennoxamine and Chilenine

A new cyclization route, triggered by epoxide opening, has been performed to provide the key intermediates for isoindolobenzapine alkaloids, lennoxamine and chilenine. The epoxide was prepared by the Stille reaction using vinyltributylstannane and the following dioxirane treatment. Cyclization under the treatment of BF₃ · OEt₂ provided an azepine moiety, and the oxidative cyclization toward the known precursor for the alkaloids has been achieved by reaction with a stoichiometric amount of Pd(OAc)₂. This formal synthesis suggests a new route to the alkaloids.