Cycloaddition reactions of 2,4-diphenyl-1,3-diazabuta-1,3-dienes with isocyanates and isothiocyanates

The cycloaddition reactions of 1-p-tolyl and 1-benzyl- 2,4-diphenyl-1,3-diazabuta-1,3-dienes with a variety of aryl and alkyl isocyanate and isothiocyanate are described. The reaction mechanism is also discussed.     

Synthesis of novel heterocyclic fused 1,3-diazabuta-1,3-dienes and accompanying rearrangements in their cycloaddition reactions with ketenes: synthesis of heterocyclic fused pyrimidinone derivatives

The reactions of 1,3-diazabuta-1,3-dienes 1 with 2-aminothiophenol have been shown to result in excellent yields of N-benzothiazol-2-yl-N′-aryl benzamidines 2. Their regioselective [4+2] cycloadditions with various ketenes are shown to yield novel benzothiazolo pyrimidinones 4. A similar and convenient protocol for the synthesis of bisthiosubstituted 1,3-diazabuta-1,3-dienes 8 and 9 and interesting rearrangements accompanying their [4+2] cycloadditions with a number of ketenes are described.     

Reaktionen von 4,4-Bis(trifluormethyl)-1,3-diazabuta-1,3-dienen. Synthese trifluormethyl-substituierter Heterocyclenvia Baylis-Hillman-Reaktion

Summary 4,4-Bis(trifluoromethyl)-1,3-diazabuta-1,3-dienes and ,-unsaturated heteromultiple bond systems react to givebis(trifluoromethyl) substituted heterocycles. The first step of the formal [4+2] cycloaddition represents aBaylis-Hillman reaction.

Prof. Dr. Rolf Huisgen zum 75. Geburtstag gewidmet     

Aromatic glyoxalimines in criss-cross cycloaddition reactions

Aromatic 1,4-diazabuta-1,3-dienes in glacial acetic acid with thiocyanates produce via criss-cross cycloaddition reactions the corresponding perhydroimidazo[4,5-d]imidazole-2,5-dithiones. When a mixture of thiocyanate and cyanate in a proper ratio was reacted together, nonsymmetrical 5-thioxo-perhydroimidazo[4,5-d]imidazole-2-ones were isolated. With cyanates substituted aromatic 1,4-diazabuta-1,3-dienes afforded product of acetic acid addition to primary formed 1,3-dipole intermediate 5-(4-substituted phenylamino)-3-(4-substituted phenyl)-2-oxoimidazolidin-4-yl acetate.     

Synthesis of chromanes by sequential ‘[3+3]-cyclization/Williamson’ reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes

Functionalized chromanes were prepared by sequential ‘[3+3]-cyclization/Williamson’ reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes with 1,1,3,3-tetramethoxypropane, 3-silyloxyalk-2-en-1-ones, and 1,1-diacetylcyclopropane. The first step of the sequence involves [3+3] cyclizations of the starting materials to give 2-(3-chloropropyl)phenols. The subsequent cyclization proceeds by intramolecular nucleophilic substitution. 6-(2-Hydroxybenzoyl)chromanes were prepared based on sequential ‘[3+3]-cyclization/Williamson’ reactions of 1,3-bis(trimethylsilyloxy)-7-chlorohepta-1,3-dienes with 3-formylchromones.     

1,3-Cycloaddition von alkinen an hetero-1,3-diene 1-aminopyrrole aus 1,2-diazabuta-1,3-dienen und 1-diethylaminopropin

1-Aminopyrroles (4) are obtained by reaction of 1,2-diazabuta-1,3-dienes (1) and ynamines (2). This reaction represents one of the very rare examples of 1,3-cycloaddition processes of alkynes and hetero-1,3-dienes.     

Heterocyclen-synthesen mit 4,4-bis(trifluormethyl)-1,3-diazabuta-1,3-dienen, II [1] spektroskopische untersuchung der isonitril- und dimethoxy-carben-addukte

[4+1] Cycloaddition reactions of 4,4-bis(trifluoromethyl)-1,3-diazabuta-1,3-dienes 3, accessible by reaction of amidines with hexafluoroacetone in the presence of dehydrating reagents, with isonitriles and dimethoxycarbene are described. Configuration of the isonitrile adducts 5 – 9 can be determined on basis of the ¹⁹F NMR data.     

Überraschende Reaktionen von 4,4-Bis(trifluormethyl)-1-oxa-3-azabuta-1,3-dienen: Tandem-Reaktion mit Acrylnitril

Summary 4,4-Bis(trifluoromethyl)-1-oxa-3-azabuta-1,3-dienes and acrylonitrile react in the presence of equimolar amounts of 4-dimethylaminopyridine (DMAP) to give 2:1-adducts. A sequential [4+2] cycloaddition is proposed.

Prof. Dr.Rolf Huisgen zum 75. Geburtstag gewidmet     

Regiospecific [2+2] cycloadditions of electron-poor acetylenes to (Z)-2-acylamino-3-dimethylaminopropenoates: synthesis of highly functionalised buta-1,3-dienes

Microwave-assisted [2+2] cycloaddition reactions of 2-amino-3-dimethylaminopropenoates with acetylenecarboxylates furnished highly functionalised 1-amino-4-(dimethylamino)buta-1,3-dienes in 40-94% yields. All reactions were observed to consistently produce single geometrical isomers, and in cases where non-symmetrical acetylenes were employed the reactions proceeded in a regiospecific manner.     

Dienophilic behavior of the vinylic (C=C) and the carbonyl (C=O) bonds of ketenes in reactions with 1,3-diazabuta-1,3-dienes

[reaction: see text] Ab initio and density functional studies (DFT) on cycloaddition reactions of 1,3-diazabuta-1,3-dienes with ketenes are reported. The vinylic (C=C) and the carbonyl (C=O) units of the ketenes are found to participate in concerted asynchronous [4 + 2] cycloaddition reactions. The transition states (3t, 4t, and 7t) for these paths have been located on the PE surface at the correlated levels of ab initio calculations. A reasonable mechanism for the formation of [4 + 2] and [2 + 2] adducts is presented.     

1,4-Diazabuta-1,3-dien-N-Sulfinylamin-Nickel(0)-Komplexe

1,4-Diazabuta-1,3-Diene-N-Sulfinylamin Nickel(0) Complexes Synthesis, properties, and reactions of 1,4-diazabuta-1,3-diene-N-sulfinylamine nickel(0) complexes are described. The highly coloured and extremely air and moisture sensitive nickel(0) complexes have been characterized by means of i.r. and ¹H n.m.r.spectroscopy. The N-sulfinylamine ligands are η²-(S,N)-side on coordinated.     

Design, synthesis, characterization, and preliminary complexation studies of chromogenic vanadophiles: 1,3-alternate thiacalix[4]arene tetrahydroxamic acids

New chromogenic supramolecular vanadophiles were designed and synthesized by incorporating hydroxamic acid chains on a 1,3-alternate thiacalix[4]arene scaffold and were found to show high affinity toward vanadate ions. The article describes a comprehensive design process to devise a tailor-made co-ordination cavity for vanadate ions by pre-organization of hydroxamic acid chelating moieties on a 1,3-alternate thiacalix[4]arene scaffold. These receptors simultaneously co-ordinate two vanadate ions giving a highly ‘staggered’ geometry with almost D_2d symmetry. Proposed structures and complexation behavior of the receptors were explained by critical examination of FTIR, UV-visible, mass, and ¹H NMR data.     

Synthesis of 1,3-dithiole-2-thiones and tetrathiafulvalenes using oligo-(1,3-dithiole-2,4,5-trithione). (Review)

Methods for the synthesis of 1,3-dithiole-2-thiones, based on [4+2] cycloaddition of the 1,3-dithiole-2,4,5-trithione oligomer to various unsaturated acyclic, carbocyclic, and heterocyclic compounds, are reviewed. Methods for the production of substituted tetrathiafulvalenes, which can be regarded as derivatives of bis(ethylenedithio)tetrathiafulvalene, from 1,3-dithiole-2-thiones synthesized by this method are described. Dedicated to the memory of Professor O. Neilands. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–502, April, 2006.     

F-Induced ‘turn-on’ fluorescent chemosensor based on 1,3-alt thiacalix[4]arene

A new thiacalix[4]arene based fluorescent sensor 1 bearing two naphthyl groups has been synthesized in 1,3-alternate conformation. In the absence of fluoride ion, the receptor 1 is in ‘off-state’ showing no fluorescence emission. The presence of fluoride ion triggered the fluorescence emission to ‘on-state’. The receptor shows pronounced selectivity for fluoride ions. In THF, the presence of F⁻ ions induces the formation of a 1:1 (G:H) complex.     

Cycloaddition of keteniminium with terminal alkynes toward cyclobuteniminium and their use in Diels–Alder reactions

An efficient access to cyclobutanone derivatives has been developed via a ‘one-pot’ [2+2]/[4+2] sequence involving keteniminium and cyclobuteniminium salts as key intermediates. A broad range of novel cyclobuteniminium salts have been prepared via [2+2] cycloaddition of keteniminium salts and alkynes. The resulting [2+2] adducts were then further transformed by Diels–Alder reaction with various dienes to afford cyclobutanone derivatives in good yields. A density functional theory (DFT) based computational study has been performed to obtain insight into the nature of the cycloaddition reactions and to investigate the difference in reactivity of cyclobuteniminium salts. Finally, the usefulness of cyclobutanone derivatives has been demonstrated by ring expansion reactions affording lactone, lactame, and cyclopentanone derivatives.     

Phosphine-mediated diverse reactivity of γ-substituted allenoates with aldehydes: syntheses of highly functionalized chromans and (E,E)-1,3-dienes

As an extension of our previous studies, the phosphine-mediated diverse reactivity of γ-substituted allenoates with aldehydes has been further investigated. Under the catalysis of tris(p-chlorophenyl)phosphine (20 mol %), ethyl 2,3-pentadienoate, namely ethyl γ-methyl allenoate, readily undergoes a formal [4+2] annulation with dual-functional salicylaldehydes, giving highly functionalized chromans in 47-97% yields. This transformation represents a novel reactivity pattern of electron-deficient allenes with aldehydes. Conversely, when the γ substituent in the allenoate changes from methyl to benzyl or the employed phosphine from weakly nucleophilic triarylphosphine to strongly trialkylphosphine, the phosphine-mediated reactivity of γ-substituted allenoates with aldehydes will be steered to a stoichiometric olefination reaction, leading to the highly stereoselective formation of (E,E)-1,3-dienes. Thus, under the mediation of equivalent PPh₃, ethyl γ-benzyl allenoate readily condenses with salicylaldehydes, affording (E,E)-1,3-dienes in 34-84% yields; with strongly nucleophilic 1,3,5-triaza-7-phosphaadamantane (PTA) used instead of PPh₃, ethyl γ-methyl allenoate also gives the corresponding olefination products in 32-73% yields with reactive aromatic aldehydes. On the basis of our previous studies and current work, these chemical transformations of γ-substituted allenoates with aldehydes, as well as their diverse reactivity, have been mechanistically rationalized.     

‘One-flask’ synthesis to 3,5-disubstituted 1,2,4-triazoles from aldehydes with hydrazonoyl hydrochlorides via 1,3-dipolar cycloaddition

A new ‘one-flask’ synthesis of 3,5-disubstituted 1,2,4-triazoles has successfully been developed to synthesize a series of 3,5-disubstituted 1,2,4-triazoles. The transformation involves the 1,3-dipolar cycloaddition reaction of hydrazonoyl hydrochlorides with oxime intermediates prepared from aldehydes with hydroxylamine hydrochloride in the presence of excess amount of triethylamine. In this ‘one-flask’ 1,3-dipolar reaction, hydrazonoyl hydrochlorides was concerned as the masked 1,3-dipole nitrilimine under basic condition. Furthermore, this newly developed methodology can be applied to various aldehyde substrates including aliphatic, cyclic aliphatic, aromatic, and heterocyclic aldehydes.     

On the importance of the pore inner cavity for the ionophoric activity of 1,3-alternate calix[4]arene/steroid conjugates

1,3-Alternate calix[4]arenes, decorated with four nonpolar ‘all-trans’ tetracyclic nuclei and cation-stabilizing β-methoxyethoxy appendages, were synthesized from commercially available starting materials and through straightforward functional groups transformations/couplings. Their Na⁺-transport activities, when compared with those exerted by the known conformationally-rigidified 1,3-alternate calix[4]arene AB/cis cholic acid conjugates, suggest that the cation conductance is related to the morphology of the pendant steroids.     

Addition reactions of 2-polyfluoroalkyl substituted 1,3-thiazolin-4-one derivatives

2-Polyfluoroalkyl-5-methoxycarbonylmethylene-thiazolin-4-ones react as dienophiles on the exo-cyclic ylidene bond to give spiro-derivatives and as 1,3-dienes with olefins to give dihydropyranothiazole derivatives. The endo-cyclic CN bond in these compounds do not enter into the cycloaddition reactions.     

Enantioselective synthesis of the spirotryprostatin A scaffold

The pentacyclic spirotryprostatin scaffold embodies an oxindole with an all-carbon quaternary stereocenter. The scaffold can efficiently be accessed in a one-pot reaction sequence consisting of a highly enantioselective 1,3-dipolar cycloaddition, N-acylation of the resulting stereochemically complex 3,3′-pyrrolidinyl-spirooxindole core with Fmoc-proline and spontaneous ring closure upon N-deprotection.