Photochemical intramolecular cyclization of o-alkynylaryl isocyanides with organic dichalcogenides leading to 2,4-bischalcogenated quinolines

When a mixture of o-alkynylaryl isocyanides and organic dichalcogenides such as diselenides or ditellurides was irradiated with light of wavelength over 300 or 400 nm, the intramolecular cyclization of the isocyanides took place to afford the corresponding 2,4-bischalcogenated quinolines selectively. The photochemical cyclization of 2-(phenylethynyl)phenyl isocyanide could also proceed in the presence of hydrogen transfer reagents such as tris(trimethylsilyl)silane, tributylgermyl hydride, alkanethiols, and benzeneselenol, providing the corresponding 3-phenylquinoline as the result of 2,4-dihydrogenation.     

Synthesis of 2-alkoxy(aroxy)-3-substituted quinolines by DABCO-promoted cyclization of o-alkynylaryl isocyanides

Diversified 2-alkoxy- and 2-aroxy-3-substituted quinolines were synthesized from o-alkynylaryl isocyanides and alcohols and phenols promoted by DABCO, respectively. The reaction was initiated by nucleophilic addition of DABCO to isocyanide and subsequent cycliztion, leading to a DABCO-quinoline-based adduct as the reactive intermediate, followed by substitution of the DABCO moiety with oxygenated nucleophiles.     

Massenspektrometrische Fragmentieungen Aomatischer Isocyanide

The mass spectra of 19 aromatic isocyanides are reported and discussed. The main feature of the fragmentation of these compounds is loss of HCN usually indicated by a metastable peak. Although this process is characteristic of the behaviour of aromatic isocyanides the extent to which it dominates the mass spectrum of any aromatic isocyanide is determined by the relative ease of cleavage of other bonds within the molecule. 2,4,6-d₃-phenylisocyanide (Ib) loses predominantly DCN from the molecular ion while 2,4-d₂-1-naphthylisocyanide (lIIb) eliminates HCN. It is therefore concluded that the loss of HCN from aromatic isocyanides is mainly a non-random process (no randomization prior to fragmentation).     

Reaction between alkyl isocyanides and dimethyl acetylenedicarboxylate in the presence of polyhydroxybenzenes. Synthesis of 4H-chromene derivatives

The reactive intermediate generated by the addition of alkyl isocyanides to dimethyl acetylenedicarboxylate was trapped by phenols such as resorcinol, catechol, hydroquinone, pyrogallol, 2,4-dihydroxybenzaldehyde, or 8-hydroxyquinoline to produce highly functionalized 4H-chromenes in fairly good yields.     

Tandem synthesis of 1-(alkylamino)-2,4-diarylpyrimido[6,1-a]isoquinolin-5-ium chlorides from isoquinoline, N-alkyl-benzimidoyl chlorides, and isocyanides

1-(Alkylamino)-2,4-diarylpyrimido[6,1-a]isoquinolin-5-ium chlorides are obtained in good yields via a tandem reaction between isoquinoline, N-alkyl-benzimidoyl chlorides and alkyl isocyanides in anhydrous acetonitrile.     

Synthesis of phenylpyrrolylpyrroles. Part II

A series of methyl or ethyl 3-(N-arylpyrrol-3-yl)-1H-pyrrole-2-carboxylates and 2,4-dicarboxylates have been synthesized using an alkyl isocyanides addition-cyclization with N-arylpyrrole derivatives such as the carboxaldehydes and nitropropenes.     

Synthesis of new phenylpyrrolylpyrroles

A series of methyl or ethyl 3-(N-arylpyrrol-2-yl)-1N-pyrrole-2-carboxylates and 2,4-dicarboxylates has been synthesized using an alkyl isocyanides addition-cyclization to N-arylpyrrole derivatives such as carboxaldehydes and nitropropenes.     

Copper- or phosphine-catalyzed reaction of alkynes with isocyanides. Regioselective synthesis of substituted pyrroles controlled by the catalyst

The copper-catalyzed reaction of isocyanides (CNCH2EWG1) 1 with electron-deficient alkynes (RC[triple bond]CEWG2) 2 gave the 2,4-di-EWG-substituted pyrroles 3 selectively, whereas the phosphine-catalyzed reaction of 1 with 2 afforded the 2,3-di-EWG-subsituted pyrroles 4. Accordingly, regioselective synthesis of substituted pyrroles has been achieved by merely choosing the catalyst.     

Reaction between isocyanides and dialkyl acetylenedicarboxylates in the presence of 2,4-dihydro-3H-pyrazol-3-ones. One-pot synthesis of highly functionalized 7-oxo-1H,7H-pyrazolo[1,2-a]pyrazoles

The reactive 1:1 intermediate produced in the reaction between isocyanides and dialkyl acetylenedicarboxylates was trapped by 2,4-dihydro-3H-pyrazol-3-ones to yield highly functionalized 7-oxo-1H,7H-pyrazolo[1,2-a]pyrazoles in fairly good yields.     

On the Reaction between Alkyl Isocyanides and Ethynyl Phenyl Ketone in the Presence of N , N ′-Dimethylbarbituric Acid

 The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and ethynyl phenyl ketone was trapped with N,N ′-dimethylbarbituric acid to produce alkyl 1,3-dimethyl-2,4-dioxo-7-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-5-carboxamides in good yields.     

One-step synthesis of N-alkyl-2-aryl-2-oxoacetamides and N,N-dialkyl-2-aryl-4H-1,3-benzodioxine-2,4-dicarboxamides

Alkyl isocyanides react with 2-hydroxybenzaldehyde or 2-hydroxy-5-nitrobenzaldehyde to afford N-alkyl-2-aryl-2-oxoacetamides and N²,N⁴-dialkyl-2-aryl-4H-1,3-benzodioxine-2,4-dicarboxamides in nearly 1:1 ratios. Treatment of 2,6-dimethylphenyl isocyanide with 2-hydroxy-5-nitrobenzaldehyde affords only the 2-oxoacetamide derivative.     

On the Reaction between Alkyl Isocyanides and Ethynyl Phenyl Ketone in the Presence of N,N′-Dimethylbarbituric Acid

Summary.  The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and ethynyl phenyl ketone was trapped with N,N ′-dimethylbarbituric acid to produce alkyl 1,3-dimethyl-2,4-dioxo-7-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-5-carboxamides in good yields. Corresponding author. E-mail: isayavar@yahoo.com Received January 8, 2002. Accepted January 14, 2002     

On the reaction between alkyl isocyanides and 3-benzylidene-2,4-pentanedione. A convenient synthetic route to densely functionalized furans

Summary Alkyl isocyanides undergo a formal [1+4] cycloaddition reaction with 3-benzylidene-2,4-pentanedione yielding multiply functionalized furan ring systems in fairly high yields. The¹H NMR spectrum of 4-acetyl-2-(N-benzylamino)-5-methyl-3-phenylfuran shows an AB pattern for the benzylic methylene protons as a result of a restricted rotation about the bond between the acetyl group and the furan ring, thus giving rise to perpendicular disymmetric planes.

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Eine einfache Synthese von hochfunktionalisierten Furanen durch Reaktion von Alkylisocyaniden mit 3-Benzyliden-2,4-pentadion

Zusammenfassung Alkylisocyanide gehen mit 3-Benzyliden-2,4-pentadion eine formale [1+4]-Cycloaddition ein, die in relativ hohen Ausbeuten zu mehrfach funktionalisierten Furansystemen führt. Das¹H-NMR-Spektrum von 4-Acetyl-2-(N-benzylamino)-5-methyl-3-phenylfuran zeigt für die benzylischen Methylenprotonen ein AB-System, da das Molekül durch die sterische Hinderung der Rotation der Acetylgruppe asymmetrisch wird.

     

Switch in stereoselectivity caused by the isocyanide structure in the rhodium-catalyzed silylimination of alkynes

The reaction of terminal alkynes with hydrosilanes and tert-alkyl isocyanides in the presence of Rh(4)(CO)(12) gives (Z)-β-silyl-α,β-unsaturated imines in good yields. On the other hand, the use of aryl isocyanides in place of tert-alkyl isocyanides leads to the formation of E isomers.     

Palladium‐Catalyzed Cyclization Reaction of o‐Haloanilines,CO2 and Isocyanides: Access to Quinazoline‐2,4(1H,3H)‐diones

Quinazoline‐2,4(1H,3H)‐diones are core structural subunits frequently found in many biologically important compounds. The reaction of 2‐​aminobenzonitrile and CO₂, which was frequently studied, only provided N3‐unsubstituted quinazoline‐2,4(1H,3H)‐dione compounds. Herein we report palladium‐catalyzed cyclization reactions of o‐haloanilines, CO₂ and isocyanides to prepare N3‐substituted quinazoline‐2,4(1H,3H)‐diones. Electron‐rich o‐bromoanilines participated in the cyclization reaction using Cs₂CO₃ at high temperature, and electron‐deficient o‐bromoaniline or o‐iodoaniline substrates conducted the reaction using CsF as base to deliver corresponding quinazoline‐2,4(1H,3H)‐dione products in good yields.     

Synthesis of Heterocycles by Formal Cycloadditions of Isocyanides

Synthetic methodology for the synthesis of heterocycles is of continuous and high interest with applications in materials, catalysis, and medicines. Multicomponent reactions are suitable tools to efficiently generate chemically diverse sets of heterocycles with sufficient structural complexity. Especially isocyanides have proven to be particularly versatile building blocks in these one‐pot processes. Due to their electronic structure, isocyanides are able to act sequentially or simultaneously as a nucleophile and an electrophile. Traditionally, isocyanides are therefore frequently used in multicomponent chemistry. In the recent literature, numerous reactions have been reported that involve formal cycloadditions of isocyanides with conjugated heterodienes. This Focus Review aims at mapping this reactivity and at providing insight into the relationship between the various reported reaction partners and the observed reactivity modes.     

Alkenyl Isocyanide Conjugate Additions: A Rapid Route to γ‐Carbolines

Isocyanides are exceptional building blocks, the wide deployment of which in multicomponent and metal‐insertion reactions belies their limited availability. The first conjugate addition/alkylation to alkenyl isocyanides is described, which addresses this deficiency. An array of organolithiums, magnesiates, enolates, and metalated nitriles add conjugately to β‐ and β,β‐disubstituted arylsulfonyl alkenyl isocyanides to rapidly assemble diverse isocyanide scaffolds. The intermediate metalated isocyanides are efficiently trapped with electrophiles to generate substituted isocyanides incorporating contiguous tri‐ and tetra‐substituted centers. The substituted isocyanides are ideally functionalized for elaboration into synthetic targets as illustrated by the three‐step synthesis of γ‐carboline N ‐methyl ingenine B.     

Isocyanides in the synthesis of nitrogen heterocycles

Isocyanides have long proved themselves to be irreplaceable building blocks in modern organic chemistry. The unique features of the isocyano group make isocyanides particularly useful for the synthesis of a number of important classes of nitrogen heterocycles, such as pyrroles, indoles, and quinolines. Several cocyclizations of isocyanides via zwitterions and radical intermediates as well as transition-metal-catalyzed syntheses of different types of heterocycles have recently been developed. Methods starting from isocyanides often have distinct advantages over alternative approaches to the same heterocycles because of their enhanced convergence, the great simplicity of most of the operations with them, and the great variety of isocyanides readily available for use. Isocyanides have also been used in some enantioselective syntheses of chiral heterocyclic compounds, including natural products as well as precursors thereof.     

Synthesis of indole derivatives via isocyanides

Fast and convenient approaches to the indole nucleus from isocyanides are reviewed as a means for the tailored preparation of conveniently functionalized indoles by using the unique reactivity of isocyanides in one-pot multicomponent and cascade reactions.     

Interaction of mono- and diisocyanoazulenes with gold surfaces: first examples of self-assembled monolayer films involving azulenic scaffolds

The formation and properties of a new class of self-assembled monolayers (SAM) of aryl isocyanides and diisocyanides based on the nonbenzenoid azulenic framework have been investigated using FTIR spectroscopy and ellipsometry. Syntheses of several new members of the isocyanoazulene family, a recently established type of aryl isocyanides, are reported as well. The FTIR spectra for the isocyanoazulene derivatives absorbed on the gold surface indicate the terminal upright coordination of every isocyanoazulene molecule studied. In addition, the ellipsometric thicknesses have been measured and are consistent with those calculated for single monolayers of the isocyanides oriented along the surface normal. Unlike SAMs of some benzenoid aryl isocyanides, the nonbenzenoid isocyanoazule-based SAMs proved resistant to oxidation, oligomerization, and isomerization into the corresponding nitriles under ambient conditions, which is an important prerequisite to their future applications.