Bis cyclic

C20H28O3 1042-33-7) see Fluoxymesterone (Sa,6a)-S,6-epoxy-17-hydroxypregnane-3,20-dione cyclic bis(l,2-ethanediyl acetal)... 

Dendrimers 5-8 were obtained by taking advantage of the versatile regiose-lective reaction developed in the group of Diederich [24], which led to macro-cyclic bis-adducts of Cgg by a cyclization reaction at the C sphere with bis-mal-onate derivatives in a double Bingel cyclopropanation [25]. Reaction of the dendritic malonates with Cgg, I2, and l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in toluene at room temperature afforded the corresponding cyclization products 5-8 (Fig. 2). The relative position of the two cyclopropane rings in 5-8 on the Cgo core was determined based on the molecular symmetry deduced from the and NMR spectra (Cs) as well as on their UV/Vis spectra. It is well estabhshed... 

In an attempt to prepare polymers of type Ic or Id from acid amides and 1,3-dichlorodisiloxanes or 1,5-dichlorotrisiloxanes, it was found that bimolecular cyclization prevailed over polycondensation and cyclic bis(silylamides) in the amido (la) or imidato (lb) isomeric forms were exclusively formed in high yields... 

More recently, this method has been extended to preparation of a variety of disulfonium dications from both acyclic and cyclic bis-sulfides, including very labile dications not observed when other methods were used.78 Thus, simple acyclic S-S dications were prepared by an intermolecular reaction of a monosulfide, a monosulfoxide and triflic anhydride.79 In the first step, reaction of triflic anhydride with dimethylsulfoxide generates a highly electrophilic80 complex 50 (dimethyl sulfide ditriflate).81 The latter reacts with dimethyl sulfide to give labile tetramethyldisulfonium dication 51 identified by NMR spectroscopy.79 In a similar manner, bis-(tetramethylene)disulfonium dication 52 is obtained from tetrahydrothiophene and its S-oxide (Scheme 17). 

The reader may recall that the enthalpy of formation of a cyclic bis-allene has been determined (see Section III.D). 

The unusual Sn3P2Cl2 cluster 20d has been isolated in 44% yield in the form of yellow crystals (Eq. 13) (39), simply by the same reaction of Id with the stannanediyls but in the presence of SnCl2. 20d represents formally an adduct of the cyclic bis(stannanediyl) phosphandi-ide 21 and SnCl2, which coordinate to each other upon their complementary Lewis acid/Lewis base sites. 

Palladium-catalyzed bis-silylation of benzynes has been achieved. Reaction of 2-trimethylsilylaryl triflates with cyclic disilanes in the presence of KF/18-crown-6 affords cyclic bis-silylation products in good yields (Equation (29)). It is crucially important to use the palladium-isocyanide catalyst.99 100... 

Cyclic aromatic disulfides, polymerization reactions of, 23 706 Cyclic (arylene) disulfides, 23 712 Cyclic batch adsorption processes, 1-613 Cyclic bis(arylene tetrasulfide)s, 23 712 Cyclic carbon, polymer materials with, 15 177... 

The formation of the heterocycle 1 from the xylylene-bis-phosphonium salt 2 and PCI3 proceeds via a detectable intermediate 3 in a cascade of condensation reactions that is terminated by spontaneous heterolysis of the last remaining P-Cl bond in a cyclic bis-ylide-substituted chlorophosphine formed (Scheme 1) [15]. The reaction scheme is applicable to an arsenic analogue of 1 [15] and to bis-phosphonio-benzophospholides with different triaryl-, aryl-alkyl- and aryl-vinyl-phosphonio groups [16, 18, 19], but failed for trialkylphosphonio-substituted cations here, insufficient acidity prohibited obviously quantitative deprotonation of the phosphonium salts, and only mixtures of products with unreacted starting materials were obtained [19]. The cations were isolated as chloride or bromide salts, but conversion of the anions by complexation with Lewis-acids or metathesis was easily feasible [16, 18, 19] and even salts with organometallic anions ([Co(CO)4] , [CpM(CO)3] (M=Mo, W) were accessible [20]. 

Scheme 27 Cyclic bis-ylides in different transition metals...

Reagents which permit protection of primary amino groups as cyclic bis-silyl derivatives have been developed. Anilines, for example, can be converted to disilazoli-dines.88... 

The treatment of the cyclic allyl sulfoximines 14 with n-BuLi gave the corresponding lithiated allyl sulfoximines 17, which upon reaction with ClTi(OiPr)3 afforded the cyclic bis (allyl) titanium complexes 18 and equimolar amounts of Ti(OiPr)4 in practically quantitative yields [14]. The hydroxyalkylation of the cyclic complexes 18 with saturated and unsaturated aldehydes also proceeded with >98% regioselectivity and >98% diastereoselectivity at the y-position and gave the corresponding Z-onti-configured homoallyl alcohols 5 in good yields [14]. 

It is noteworthy that stereoselectivities were high, even with sterically demanding substituents at the double bond. Similarly, the treatment of the cyclic bis (allyl) titanium complexes 18 with the imino esters 23a-c afforded the corresponding B-syn-configured cyclic unsaturated amino acid derivatives -25 and the Z-syn-configured isomers Z-25 with >98% regioselectivity and >98% diaste-reoselectivity in good yields. 

Disilanes connected via both the Si-Si bond and an organic or an organo-metallic linkage are activated toward reaction with unsaturated substrates to form cyclic bis(silyl) products. Reactions of 3,4-benzo-l,l,2,2-tetraethyl-1,2-disilacyclobutene with diphenylacetylene or benzaldehyde catalyzed by Ni(PEt3)4 proceed with addition across the multiple bond to form the ring-expanded product.54 A second product is formed in a lesser amount in the case of diphenylacetylene, with insertion into the Si-C bond [Eq. (13)]. 

A wide variety of disilanyl-substituted terminal alkenes undergo regio-and stereoselective intramolecular double silylation to yield cyclic bis(silyl) ring closure products [Eq. (16)].59abe... 

Double silylation is also observed in the reaction of a,/3-unsaturated ketones with a bis(disilanyl)dithiane, resulting in high yields of cyclic silyl enol ethers [Eq. (65)].58 The catalyst for this reaction is a cyclic bis(silyl)pal-ladium(II) bis(ferf-butyl isocyanide) complex. Analogous reactions of ester... 

Activation of two Si—Si bonds in bis(disilanyl)alkanes with palladium(O) bis(tert-alkyl isocyanide) induced the formation of the cyclic bis(silyl)palladium(II) bis(terf-alkyl isocyanide) complexes (100) and disilanes described schematically in Scheme 42. These complexes were found to react with phenylacetylene, affording different amounts of five-membered cyclic products and acyclic products which are derived from the insertion of the alkyne into the general intermediate complex 101 (Scheme 42, equation 54). The bis(silanyl)dithiane palladium complex (102) was isolated and characterized in the solid state the two silicon atoms, the two isocyano carbons and the palladium atom are nearly in a plane with a short cross-ring Si—Si distance of 2.613(2) A, suggesting the possibility of covalently bonded two Si—Si atoms in the four-membered ring. Similar reaction with cyclic disilanes afforded oligomers, and cyclic 20-membered compounds have been prepared in the presence of nitriles248,249. 

Hashimoto T, Irita H, Takaoka S, Tanaka M, Asakawa Y (2000) New Chlorinated Cyclic Bis(bibenzyls) from the Liverworts Herbertus sakuraii and Mastigophora diclados. Tetrahedron 56 3153... 

It is also possible to form novel polysilazanes by dehydrocyclodimerization of the ammonolysis product of CH3SiHCl2, or coammonolysis products of this silane with other chlorosilanes.33 Ring compounds that contain the desired Si and N atoms may also be used as starting materials, followed by hydrolysis, thermolysis, polymerization, or copolymerization to convert them into silazane-type materials. Examples are cyclic bis (silyl) imidates, /V-acylcyclosilazoxanes, /V-arylcyclosilazoxanes, and A,A,-diarylcyclosilazanes.34... 

Cyclic amino-carbenes, in molybdenum carbonyls, 5, 457 Cyclic bis(phosphine) dichlorides, with iron carbonyls, 6, 48 Cyclic carbenes, as gold atom ligands, 2, 289 Cyclic carbometallation, zirconium complexes, 10, 276 Cyclic carbozirconation characteristics, 10, 276 intermolecular reactions, 10, 278 intramolecular reactions, 10, 278 Cyclic dinuclear ylides, and gold , 2, 276 Cyclic 1,2-diols, intramolecular coupling to, 11, 51 Cyclic enones, diastereoselective cuprate additions, 9, 515 Cyclic esters, ring-opening polymerization, via lanthanide catalysis, 4, 145 Cyclic ethers... 

A chromophore such as the quinone, ruthenium complex, C(,o. or viologen is covalently introduced at the terminal of the heme-propionate side chain(s) (94-97). For example, Hamachi et al. (98) appended Ru2+(bpy)3 (bpy = 2,2 -bipyridine) at one of the terminals of the heme-propionate (Fig. 26) and monitored the photoinduced electron transfer from the photoexcited ruthenium complex to the heme-iron in the protein. The reduction of the heme-iron was monitored by the formation of oxyferrous species under aerobic conditions, while the Ru(III) complex was reductively quenched by EDTA as a sacrificial reagent. In addition, when [Co(NH3)5Cl]2+ was added to the system instead of EDTA, the photoexcited ruthenium complex was oxidatively quenched by the cobalt complex, and then one electron is abstracted from the heme-iron(III) to reduce the ruthenium complex (99). As a result, the oxoferryl species was detected due to the deprotonation of the hydroxyiron(III)-porphyrin cation radical species. An extension of this work was the assembly of the Ru2+(bpy)3 complex with a catenane moiety including the cyclic bis(viologen)(100). In the supramolecular system, vectorial electron transfer was achieved with a long-lived charge separation species (f > 2 ms). 

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