One-pot synthesis of cyclopentane-fused 5'-aryl-4-cycloalkylamino-2,2'-bipyridines via the aza-Diels–Alder/SNipso reactions

One-pot synthesis of cyclopentane-fused 5'-aryl-4- cycloalkylamino-2,2'-bipyridines based on the neat (200 °C) reaction of 3-(4-bromopyridin-2-yl)-1,2,4-triazines with enamines is reported. In the course of the transformation, consecutive aza-Diels–Alder reaction and nucleophilic substitution of bromine atom under the action of the liberating amine occur. The possibility of the solvent- and catalyst-free replacement of 4-positioned bromine atom in 2,2'-bipyridines by amino moieties was demonstrated.     

Synthesis of Substituted Tricyclo[5.3.1.04,9]undecan‐2,6‐dione from 4,4‐Disubstituted Cyclohexanone Enamines and Methacryloyl Chloride

Morpholine enamines 4‐acetyl‐4‐methyl‐1‐morpholinocyclohexene 4a, 4‐acetyl‐4‐phenyl‐1‐morpholinocyclohexene 4b, and 4‐acetyl‐4‐isopropenyl‐1‐morpholinocyclohexene 4c react with methacryloyl chloride to give 1,7‐dimethyl‐4(N‐morpholino) tricyclo[5.3.1.0^4,9]undecan‐2,6‐dione 9a , 1‐phenyl‐7‐methyl‐4(N‐morpholino) tricyclo[5.3.1.0^4,9]undecan‐2,6‐dione 9b , and 1‐ispropenyl‐7‐methyl‐4(N‐morpholino) tricyclo[5.3.1.0^4,9]undecan‐2,6‐dione 9c respectively, along with the corresponding substituted adamandane‐2,4‐diones.     

Amine‐Catalyzed Enantioselective 1,3‐Dipolar Cycloadditions of Aldehydes to C,N‐Cyclic Azomethine Imines

Amine‐catalyzed enantioselective 1,3‐dipolar cycloadditions of aldehydes to C,N‐cyclic azomethine imines were developed. The reactions between diversely substituted C,N‐cyclic azomethine imines and aldehydes proceeded smoothly in the presence of chiral prolinol silyl ether catalyst and gave the C‐1‐substituted tetrahydroisoquinolines in a highly stereoselective manner. These tetrahydroisoquinolines could be efficiently transformed to several other useful polycyclic frameworks.     

Uncatalyzed Hydroamination of Electrophilic Organometallic Alkynes: Fundamental,Theoretical, and Applied Aspects

Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and “click” chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully “green”. A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans‐enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two‐step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear‐optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push–pull conjugation in these cobalticenium– and Fe– and Ru–arene–enamine complexes due to planarity or near‐planarity between the organometallic and trans‐enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms.     

Cascade synthesis of 3-aza-bicyclo[3.1.0]hex-2-ene derivatives from N-allyl enamines

An efficient iodine-mediated cascade synthesis of 3-aza-bicyclo[3.1.0]hex-2-ene derivatives from easily prepared N-allyl enamines has been developed. The advantages of the reaction include facilitative preparation of substrates 3a–t, good functional group tolerance and transition-metal-free conditions.     

Synthesis of tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone

A general strategy for the assembly of previously unknown tris(β,β,γ-oximinoalkyl)amines from aliphatic nitro compounds and methyl vinyl ketone is described. The strategy involves N,N-bis(siloxy)enamines as key intermediates. The latter are accessible by double silylation of alkylnitro compounds. Nickel(II) and copper(II) complexes of tris(β,β,γ-oximinoalkyl)amines are prepared and structurally characterized.     

Studies on 2-Aminothiophenes: Synthesis,Transformations, and Biological Evaluation of Functionally-Substituted Thiophenes and Their Fused Derivatives

Abstract

Heterocyclic enamines1 reacted with ethyl acetoacetate to afford the corresponding amide derivatives2. Treatment of2 with carbon disulphide yielded the dipotassium salts3which reacted in-situ with a variety of α -haloketones to give the respective substituted thiophenes5,8, and13. The reactivity of the latter products towards various chemical reagents was studied to yield their fused thiophene derivatives7,10,12, and14, respectively. Some representative compounds were tested for antimicrobial activity.     

Very Simple One-Step Synthesis of Vinylphosphonates and Enamine Phosphonates by Direct Addition of Organolithium Reagents to 1-Alkynylphosphonates

Abstract

Direct addition of organolithium to 1-alkynylphosphonates (1) afforded vinylphosphonates and enamine phosphonates (2) in good to excellent yields. The reaction was carried out in dry THF at low temperature and proved to be completely stereoselective (syn addition). Alkyl, aryl, and haloalkyl groups were attached to the alkynyl entity, so the resulting vinylphosphonates contained various functional groups. The stereochemistry of the products as well as mechanism of the reaction were determined based on ¹H and ¹³C NMR. The synthesis of enamine phosphonates in the absence of complicated, highly expensive organometallic catalysis has not been previously reported.