Stereoselective synthesis of heterocyclic cage compounds by domino conjugate additions

Heterocyclic cage compounds have been stereoselectively synthesized from enantiopure [(S)R]-[(p-tolylsulfinyl)methyl]-p-quinols or their amine analogues and 2-(trimethylsilyloxy)furan in the presence of Bu4NF. The method is particularly valuable not only because of the stereochemical control but also because the reactions occur in an experimentally simple one-pot procedure through a domino sequence of three consecutive conjugate additions. The intermediate 1,4-adducts could be isolated when the reaction was carried out in the presence of BF3 x OEt2.     

Domino reactions of 4,5-dicyanopyridazine with dihydroheterocycles: synthetic and mechanistic features

The title pyridazine 1 was found to react with both 2,3-dihydrofuran (2) and 3,4-dihydro-2H-pyran (9) to give the tetracyclic skeletons 5-8 and the phthalonitrile 12 through the intermediates 4 and 10, respectively. A more complex mechanism was ascertained for the reaction of 1 with the pyrroline 14 which, under suitable conditions, afforded the bicyclic derivative 19 as the predominant product; selective elaborations of this species into the 5,6-dicyanoindoles 22 and 23 are reported.     

A domino pericyclic route to polysubstituted salicylic acid derivatives: four sequential processes from enynones and ketene silyl acetals

Alkenyl alkynyl ketones and ketene silyl acetals (KSAs) undergo regioselective [2+2]-cycloaddition under thermal conditions, triggering domino pericyclic reactions en route to various poly-substituted salicylic acid derivatives.     

The domino chemistry approach to molecular complexity: competing domino processes modulated by the substitution pattern

Oxidative cleavage with lead tetraacetate results in the synthesis of different oxygen heterocycles starting from the same unsaturated 1,2-diol of type I by tuning of the substitution pattern at the angular position. When this compound bears a functional substituent, such as an alkoxy, ester, alkenyl, or simply a hydrogen, more than one reaction pathway are in competition. The process allows for the selective formation of three different complex ring systems, by the appropriate choice of the angular substituent, leading to either a ring-expanded type 1, ring-retained type 2, or domino products 3.     

An escapade in the world of sulfenate anions: generation,reactivity and applications in domino processes

An escapade in the world of sulfenate anions is described and shows that these nucleophiles, despite being described as unstable species, are mild and efficient sulfinylating agents, allowing access to a variety of allyl and aryl sulfoxides under smooth and operationally very simple conditions. Their use in asymmetric catalysis is also possible allowing the preparation of enantio-enriched sulfoxides. Moreover, such anions have been involved in the development of two new pseudo–domino processes.     

Reaction of 2-phenyl-3-acetyl-4,5 -benzo-1,3,2-oxazaphospholane with dienes

Russian Chemical Bulletin - 2-Phenyl-3-acetyl-4,5-benzo-1,3,2-oxazaphospholane reacts with conjugated dienic hydrocarbons to give phospholenes and 2-methylbenzoxazole.     

Development of domino processes by using 7-silylcycloheptatrienes and its analogues

7-Silyl- and 7-silylmethylcycloheptatrienes were shown to react with acylnitroso reagents at room temperature, through their norcaradiene forms, to generate the corresponding cycloadducts 5?a-b and 6?a-b as single diastereomers. The course of the reaction was dramatically modified by changing the reaction conditions. Using a polar medium, functionalized cyclohexa-1,3-dienes 7?a-b and bicyclic compounds 13?a-b were instead generated, incorporating one or two amino groups. Similar behavior was observed by using other dienophiles, including triazolinedione, but also activated aldehydes and ketones. A tentative mechanism has been proposed to rationalize the formation of both classes of products that relies on a domino process involving four consecutive elementary steps, in this order: 1)?electrocyclic process, 2)?hetero-Diels-Alder reaction, 3)?cyclopropane ring opening, and 4)?hetero-Diels-Alder reaction. Trapping of the cationic intermediate and isolation of the primary cycloadduct provide support for this hypothesis. An enantioselective version of the cascade using cycloheptatriene 4?b and aldehydes and ketones, under copper(II) catalysis was also carried out, leading to cyclohexa-1,3-dienes 21, 28, and 30 with enantioselectivities up to 93?% ee. Finally, elaboration of the intermediates above has been carried out, opening a straightforward access to sugar mimics 42-43 and complex polycyclic systems 36 and 39.     

Palladium-catalyzed carbohalogenation: bromide to iodide exchange and domino processes

Aryl bromides have been used to prepare a variety of nitrogen- and oxygen-containing heterocycles featuring new carbon-carbon and carbon-iodine bonds. This palladium-catalyzed carbohalogenation requires potassium iodide for the reaction to proceed in high yields. Additionally, the first examples of domino carbohalogenation reactions have been demonstrated using both aryl iodide and aryl bromide starting materials. Complex products with multiple rings and stereogenic centers are generated in excellent yields with moderate to excellent diastereoselectivities.     

Fluorinated compounds for advanced IC interconnect applications: a survey of chemistries and processes

The semiconductor industry is now in the early stages of an unprecedented change in materials set for the integrated circuit (IC) interconnect structure. The traditional layers of aluminum conductors and silicon dioxide dielectrics are being replaced by copper thin films and a variety of low k candidates, respectively. In many cases, fluorine confers desirable properties on either the precursors or the final films. At the same time, fluorine presents some potentially adverse effects, which have led to a so-called “fear-of-fluorine” in interconnect applications. This paper will review the proposed uses of fluorinated compounds in the interconnect structures, covering both precursors and the resulting thin films. Both the status of technical studies, and the prospects for commercial implementation, will be addressed.     

Thermal rearrangement of cage lactones and related compounds — dyotropic rearrangement of cage compounds

Thermolyses of cage lactones ($\text{2}$) and their corresponding lactols ($\text{7}$) cause a formal dyotropic rearrangement. These novel reactions in cage system are discussed.     

Diels–Alder adducts of maleic ­anhydride and dienes: new compounds by crystallization

We have determined the crystal structures of bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic anhydride, C₉H₈O₃, (I), 1,2,3,4,7,7‐hexa­chloro­bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic anhydride diethyl ether solvate, C₉H₂Cl₆O₃·0.16­C₄H₁₀O, (II), bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic acid, C₉H₁₀O₄, (III), 1,2,3,4,7,7‐hexa­chloro­bi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5,6‐di­carboxyl­ic acid, C₉H₄Cl₆O₄, (IVa) and (IVb), and ethyl 1,2,3,4,7,7‐hexa­chloro‐6‐carboxybi­cyclo­[2.2.1]­hept‐2‐ene‐endo‐cis‐5‐carboxyl­ate monohydrate, C₁₁H₈Cl₆O₄·H₂O, (V). Compounds (I) and (II) were prepared by a standard Diels–Alder reaction from maleic anhydride and cyclo­penta­diene or hexa­chloro­cyclo­penta­diene, respectively. The crystal‐growing processes of these compounds led to surprising results: rapid recrystallization of (I) from diethyl ether and (II) from petroleum ether gave crystals of these compounds, however, crystallization by slow evaporation techniques using common solvents yielded new compounds in which the five‐membered heterocycle has been cleaved.     

Synthesis and 20π-electrocyclisation of heptahendecafulvadiene - An unusual sequence of pericyclic processes

Upon thermal activation the newly synthesised heptahendecafulvadiene E ( 3) is isomerised into the pentacyclic hydrocarbons 9/11 (xylene,t_1/2(150°C) ca.5min), the formation of which is explained by initial conrotatory 20-electron electrocyclisation followed by a cascade of 10π/6π-pericyclic processes.     

Computer simulation of cage processes and some difficulties with present models

A simple model involving random displacements of particles in a cubic lattice is used to evaluate the importance of primary and secondary recombination in cage processes and leads to estimates of the lifetime of cage pehnomena. However, it is pointed out that all such models, and treatments which attempt to relate processes at the molecular level with bulk viscosity or diffusion constants, are inherently qualitative since they ignore the important correlation between motions of neighboring molecules.     

Palladium-catalyzed addition of mono- and dicarbonyl compounds to conjugated dienes

An intermolecular, palladium-catalyzed addition of the alpha-C-H bond of monocarbonyl and 1,3-dicarbonyl compounds to dienes has been developed, and an exploration of the scope of these reactions with a broad range of carbonyl compounds and nitriles was conducted. The combination of CpPd(allyl) and the commercially available 1,3-bis(dicyclohexylphosphino)propane (DCyPP) catalyzed the 1:1 addition of the C-H bonds of these substrates to dienes in high yields. These reactions included unusual additions of the C-H bonds of ketones, lactones, esters, and nitriles to dienes, as well as the more common additions of cyanoesters, malononitrile, and alpha-sulfonyl esters. Reactions of these substrates with both cyclic and acyclic dienes are reported. Reactions catalyzed by complexes of nonracemic chiral ligands were also conducted, and the first enantioselective version of this reaction was achieved with a Josiphos ligand with enantioselectivities up to 81%.     

Synthesis of macrocyclic cage compounds by diamine-dihalide one-step coupling reaction

Macropolycyclic cage compounds were synthesized by a direct reaction between diamines and bis(bromomethyl) compounds. The procedure for constructing the polycyclic cage structure is simple and straightforward. The macropolycyclic compounds obtainable from this cyclization procedure are three-dimensional cage compounds, and any other isomers were not obtained except for two examples. Benzene, pyridine, and aliphatic units could be introduced into the cage structure. The macrocycles that have strong cation affinity were obtained as their potassium complexes.     

Stereoselective Synthesis of Polyfunctionalized Nitrothianes: Enhancement of Stereoselectivity by Microwaves

The Michael addition of nitromethane to (Z,Z)-2,2′-thiobis(1,3-diarylprop-2-en-1-ones) in the presence of NaOEt in dimethylformamide (DMF)/alcohol under thermal conditions affords a diastereomeric mixture of 2a,6e-diaroyl-3a,5e-diaryl-4e-nitrothianes and 2e,6e-diaroyl-3e,5e-diaryl-4e-nitrothianes with a dr of ～3:1/4:1 respectively. This reaction under microwave irradiation in DMF/alcohol afforded solely 2a,6e-diaroyl-3a,5e-diaryl-4e-nitrothianes, disclosing enhancement of stereoselectivity by microwaves.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file.     

Bile acid-based cage compounds with lipophilic outer shells and inner cavities

The uniquely functionalized steroid-based cyclodimers 4, cis-5, and trans-5 have been synthesized and fully characterized.The cyclodimer 5, with a cis-trans ratio of 3:1, is obtained by coupling the terminal alkenes of two 4-pentenoate groups on a cyclodimer 4 via Grubbs' intramolecular ring-closing metathesis. The crystal structure shows cis-5 to be a cagelike cyclic oligomer bridged by the flexible oct-4-enedioate link.