First Diels-Alder Addct of [60] Fullerene with a Piperidinoxanthate

In the search for intramolecular energy and electron transfer phenomena in [ 60 ] fullerene donor-containing molecules, some electron donor fragments have been covalently linked to the fullerene core. [1 ～4] Only in very fewcases has reliable evidence of thermal or photoinduced intramolecular electron transfer processes been reported. [5]With the aim of promoting an intramolecular electron transfer we sought to develop a novel type of 6-chlorophenazine derivative of [60]fullerene in which the 6-chloro-phenazine core is directly attached by two σ-bonds to the ball giving rise to a different and more rigid spatial orientation of the HOMO of the 6-chloro-phenazine addend with respect to the LUMO of [60]fullerene.     

Rhodium N-heterocyclic carbene-catalyzed [4 + 2] and [5 + 2] cycloaddition reactions

[reactions: see text] A rhodium complex of N-heterocyclic carbene (NHC) has been developed for intra- and intermolecular [4 + 2] and intramolecular [5 + 2] cycloaddition reactions. This is the first use of a transition-metal NHC complex in a Diels-Alder-type reaction. For the intramolecular [4 + 2] cycloaddition reactions, all the dienynes studied were converted to their corresponding cycloadducts in 91-99% yields within 10 min. Moreover, up to 1900 turnovers have been obtained for the intramolecular [4 + 2] cycloaddition at 15-20 degrees C. For the intermolecular [4 + 2] cycloadditions, high yields (71-99%) of the corresponding cycloaddition products were obtained. The reaction time and yield were highly dependent upon the diene and the dienophile. For the intramolecular [5 + 2] cycloaddition reactions, all the alkyne vinylcyclopropanes studied were converted to their corresponding cycloadducts in 91-98% yields within 10 min. However, the catalytic system was not effective for an intermolecular [5 + 2] cycloaddition reaction.     

Diazocarbonyl derivatives of heterocycles. 6. Intramolecular reactions of 2-carbomethoxy-3-diazoacetylquinoline

Treatment of 2-carbomethoxy-3-diazoacetylquinoline with mineral acids results in an intramolecular reaction leading to the formation of 6H-2,5-dioxopyrano-[3,4-b]quinoline; in the presence of bases the intramolecular condensation product is 2-diazo-1,3-dioxocyclopenteno[4,5-b]-quinoline. Treatment of 2-carbomethoxy-3-diazoacetylquinoline with sodium methoxide results in a reversible intramolecular rearrangement via migration of the diazomethine fragment and formation of the isomeric 3-carbomethoxy-2-diazoacetylquinoline.For communication No. 5 see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 959–962, July, 1987.     

Total synthesis of sordaricin

[structure: see text] The total synthesis of sordaricin, the diterpene aglycone of an important class of antifungal compounds, is described. Two approaches were explored, the first of which utilized a possible biogenetic intramolecular [4 + 2] cycloaddition to form the complete carbon skeleton of the target molecule. A second approach using a tandem cycloreversion/intramolecular [4 + 2] cycloaddition sequence is also detailed.     

Intramolecular N-arylation in heterocyclization: synthesis of new pyrido-fused pyrrolo[1,2-a][1,4]diazepinones

Alkylation of l-prolinamide with 3-(chloromethyl)-2-halopyridines, followed by cyclization through an intramolecular Pd-catalysed amidation, provided an entry to the pyrido[2,3-e]pyrrolo[1,2-a][1,4]diazepin-10-one scaffold. Furthermore, a synthetic route towards diverse new pyrido[f]pyrrolo[1,2-a][1,4]diazepin-7-ones has been developed by acylation of contiguously substituted (aminomethyl)halopyridines with Boc-l-proline followed by intramolecular amination.     

Molecular recognition of anions through hydrogen bonding stabilization of anion-ionophore adducts: a novel trifluoroacetophenone-based binding motif

[reaction: see text] A novel trifluoroacetophenone-based binding motif has been developed that recognizes anions such as carboxylates through reversible formation of anion-ionophore adducts that are stabilized by intramolecular H-bonding. The intramolecular H-bonding resulted in more than 10-fold enhancement in the binding affinity and an enthalpy gain (DeltaH degrees ) of 3.0 kcal/mol for the binding of an acetate ion when compared to the case without the intramolecular H-bonding.     

Lewis acid-catalyzed rearrangement of multi-substituted arylvinylidenecyclopropanes

An interesting rearrangement of arylvinylidenecyclopropanes having three substituents at the 1- and 2-positions of the corresponding cyclopropane catalyzed by Lewis acids to give 6aH-benzo[c]fluorine derivatives via a double intramolecular Friedel-Crafts reaction or to give an indene derivative via an intramolecular Friedel-Crafts reaction is described.     

Development of efficient Lewis acid catalysts for intramolecular cycloaddition reactions of ester-tethered substrates

We have developed novel bidentate Lewis acids that efficiently promote the intramolecular cycloaddition reactions of ester-tethered substrates. Bis-aluminated triflic amide derivatives [TfN(AlR(1)R(2))2], which are generated by simply mixing triflic amide and 2 equiv of methyl aluminum or aluminum hydride, catalyzed intramolecular Diels-Alder (DA) reactions of ester-tethered 1,7,9-trienes and intermolecular DA reactions of alpha,beta-unsaturated lactones. We also found that bimetallic Lewis acid derived from 1,1'-biphenyl-2,2'-di(triflyl)amide and dimethylaluminum chloride promoted the intramolecular [3 + 2] cycloaddition reaction of acrylate derivatives having an allylsilane part.     

Multi-maleimides bearing electron-donating chromophores: reversible fluorescence and aggregation behavior

A((=))-D, [A((=))](2)-D and [A ((=))](3)-D multi-maleimides and multi-itaconimides bearing electron-donating chromophores display a strong fluorescence quenching due to an intramolecular charge-transfer interaction. The electron-accepting C=C bond plays a key role in the intramolecular quenching. For the isomerization of these multi-itaconimides and Michael additions of these multi-maleimides, their emission behavior is irreversible. For the Diels-Alder additions of these multi-maleimides, their emission behavior is reversible due to the reversible opening and closing of intramolecular charge-transfer pathway. Tris-maleimide TMPA peripherally modified with furfural alcohol displays not only reversible fluorescence behavior but also reversible aggregation behavior.     

Anion radical chain cycloaddition of tethered enones: intramolecular cyclobutanation and Diels-Alder cycloaddition

[reaction: see text] The anion radicals of certain bis(enones), generated by cathodic reduction, are observed to participate in intramolecular cyclobutanation, yielding bicyclo[3.2.0]heptane derivatives through an anion radical chain mechanism. Evidence for stepwise cycloaddition involving distonic anion radical intermediates is presented. In addition to the novel anion radical cyclobutanations, an unprecedented intramolecular anion radical Diels-Alder product is observed. Parallel trends in substrate scope vis-à-vis the Co-catalyzed bis(enone) cyclobutanation are discussed.     

Total synthesis of jimenezin via an intramolecular allylboration

[structure: see text] An efficient total synthesis of the annonaceous acetogenin jimenezin was achieved. The key steps used were a highly stereoselective intramolecular allylboration to establish the tetrahydropyran ring and an intramolecular Williamson reaction to close the tetrahydrofuran ring.     

Highly enantioselective syntheses of heterocycles via intramolecular Ir-catalyzed allylic amination and etherification

[reaction: see text] Enantioselective Ir-catalyzed intramolecular allylic aminations and etherifications are described. Up to 97% ee was achieved using catalysts prepared by in situ activation of mixtures of phosphorus amidites and [Ir(COD)Cl]2. Sequential aminations of bis-allylic carbonates, involving an inter- followed by an intramolecular reaction, gave trans-N-benzyl-2,5-divinylpyrrolidine and trans-N-benzyl-2,6-divinylpiperidine with > or = 99% ee. New phosphorus amidites as well as improved conditions for intermolecular aminations are reported.     

A new entry to polycyclic indole skeletons via palladium-catalyzed intramolecular heteroannulation

[reaction: see text] A one-step method was developed for elaboration of a variety of polycyclic indole skeletons via a novel palladium-catalyzed intramolecular indolization of 2-chloroanilines bearing tethered acetylenes. This novel intramolecular indolization method unveils an unusual syn amidopalladation pathway of a tethered alkyne.     

Lewis Acid-Catalyzed Intramolecular [2 + 2] Cycloaddition of alpha-Ester-Substituted Conjugated Dienyl- and Trienylphosphonates. New Synthesis of Functionalized Cyclic Terpenoids

alpha-Ester-substituted 1,3-dienylphosphonates 7 and 8, prepared by the Knoevenagel condensation, underwent intramolecular [2 + 2] cycloaddition in the presence of Lewis acid to form bicyclo[4.2.0] (26-57% yield) and bicyclo[3.2.0]skeleton (14-38% yield), respectively. Similar treatment of homologous 1,3-dienylphosphonate 11 and 1,3,5-trienylphosphonate 12 resulted in the formation of ionone derivatives (30-94% yield). The intramolecular cycloaddition reaction was applicable to several conjugated dienes bearing an ester group.     

Catalytic Asymmetric Intramolecular [4+2] Cycloaddition of In Situ Generated ortho‐Quinone Methides

Herein, we describe the first catalytic asymmetric intramolecular [4+2] cycloaddition of in situ generated ortho‐quinone methides. In the presence of a confined chiral imidodiphosphoric acid catalyst, various salicylaldehydes react with dienyl alcohols to give transient ortho ‐quinone methide intermediates, which undergo an intramolecular [4+2] cycloaddition to provide highly functionalized furanochromanes and pyranochromanes in excellent diastereoselectivity and enantioselectivity.     

New perspectives in the chemistry of 1-azidohydrazones

Thermal decomposition of 1-azidohydrazones [I] results in tricyclic products [III], probably arising from nitrene intermediates through an intramolecular cycloaddition to the ethylenic bond.     

Asymmetric synthesis of ABC tricyclic systems in Daphniphyllum alkaloid

Efficient synthetic routs for the direct and rapid construction of[5-6-6]ABC tricyclic systems of daphmanidin A-type and calyciphylline A-type alkaloids have been successfully developed.For the daphmanidin A-type,the synthesis of[5-6-6]tricyclic framework utilize a HCl-mediated intramolecular Aldol reaction to construct the bicyclo[2.2.2]octane core and a thermal condensation to afford the ABC ring system.In addition,for the calyciphylline A-type,an improved synthesis of ABC[5-6-6]tricyclic system was developed,featuring an introduction of methyl ester group at C2 before the Pd-catalyzed intramolecular oxidative alkylation to construct the desired bowl-shape tricyclic core with stereochemical control.     

Thermische und photochemisch induzierte intramolekulare, 1,3-dipolare Cycloadditionen von 4-Phenyl-3-(2-allylphenyl)-sydnon. Vorläufige Mitteilung. 53. Mitteilung über Photoreaktionen

Thermal and photochemically induced intramolecular 1,3-dipolar cycloaddition reactions of 4-phenyl-3-(2-allylphenyl)-sydnone The title compound 9 was synthesised in the usual way, starting from 2-allylaniline and ethyl 2-bromo-2-phenylacetate, via the nitrosaminacid 8 (Scheme 2). 9 reacts at room temperature with its potential azomethinimine-function in an intramolecular [3+2]-cycloaddition to give the tricyclic compound 11 (Scheme 2). On irradiation, 9 yields the dihydro-3H-pyrazolo[2,3-a]indole 10 which probably arises by intramolecular [3+2]-cycloaddition of the corresponding intermediate nitrilimine.     

Intramolecular [2 + 2]cycloadditions of dialkylketenes with alkenes. Regiochemistry of intramolecular [2+2]cycloadditions of ketenes with alkenes

Unsaturated dialkylketenes 7a, 7b and 7c undergo intramolecular [2 + 2]cycloadditions to give 8a (45%), 9b (23%) and 9c (45%). Intramolecular cycloadditions of dialkylketenes give higher yields than intramolecular cycloadditions of monoalkylketenes, even though dialkylketenes are less reactive than monoalkylketenes. An intramolecular competition experiment with ketene 17 establishes that trans-alkenes are approximately 33 times more reactive than cis-alkenes in intramolecular cycloadditions. Ketene 36 furnishes 22% of the expected bicyclo[3.2.0]heptanone 37 and 28% of bicyclo[3.1.1]heptanone 38.     

Tandem cycloaddition reactions of allenyl diazo compounds forming triquinanes via trimethylenemethane diyls

A tandem reaction strategy for forming triquinanes from linear allenyl diazo compounds through an intramolecular 1,3-dipolar cycloaddition reaction of an allenyl diazo group that generates a trimethylenemethane (TMM) diyl followed by an intramolecular [2 + 3] TMM diyl cycloaddition reaction has been developed. The new tandem cycloaddition reaction is readily applicable to the synthesis of complex molecules with high versatility and efficiency.