Bis tetrahydrofuran

Scheme 8.2 Kishi s method for the construction of the bis(tetrahydrofuran) core of isolasalocid A.

These changes are more consistent with an /-effect, rather than an R-effect, on the B—C bond. That such diborylacetylenes have a diminished electron density at boron relative to alkyl- and vinylboranes is evident from their enhanced Lewis acidity bis(diethylboryl)acetylene (40) forms a bis(tetrahydrofuran) complex, as is evident from the1 B NMR spectrum37 (Eq. 11). Alkyl- and vinylboranes exhibit no such shifts in their11B signals in THF solution. 

The reductive coupling of guaiazulene, a fulvalene analog, with activated calcium in THF affords a 60 40 mixture of two isomers, 8,8 -147 (Figure 75) and 8,6 -(diguaiazulenide)bis(tetrahydrofuran)calcium, respectively. Thermolyses of each isomer revealed that the 8,8 -isomer is the thermodynamically preferred isomer, and it forms preferentially when the coupling is performed at 67 °C.342... 

The analogous triphenylzincate 60 and trimesitylzincate 61 were obtained by the treatment of zinc bromide bis(tetrahydrofuranate) with the respective Grignard reagents, as outlined in Scheme 48.1... 

More complex molecules can also be synthesized employing the Williamson procedure. Thus, on treatment with NaH, the mesylate 86 provides the tetrahydrofuran in excellent yield and stereo-control . In a similar manner, tosylate 87 undergoes the same reaction to lead to the bis-tetrahydrofuran <00EJO1889>. 

Stereoselective intramolecular oxymercuration of carbohydrate derivatives was proposed as the key reaction for efficient preparation of mono- and dihydroxylated unsymmetrical bis-tetrahydrofuran skeletons present in naturally occurring biologically active acetogenins. The trans- and. mz-selective intramolecular oxymercurations were explored in an enantioselective synthesis of the bis-tetrahydrofuran skeleton of mucoxin (Fig. 57).73... 

The explosive carbonylalkali-metals , previously formulated as monomeric compounds, are either dimeric acetylene derivatives of the general formula MOC=COM. or are trimers of the latter and formulated as salts of hexahydroxybenzene. Many true carbonylmetal complexes are air-sensitive and pyrophoric, not always immediately. Individually indexed compounds are Bis(dicarbonylcyclopentadienyliron)-bis(tetrahydrofuran)magnesium, 3835... 

Bis(cyclopentadienyl)phenylvanadium, 3705 Bis(cyclopentadienyl)titanimn, 3295 Bis(cyclopentadienyl)titanium selenate, 3293 Bis(cyclopentadienyl)zirconium, 3296 Bis(dicarbonylcyclopentadienyliron)-bis(tetrahydrofuran)magnesium, 3835... 

Bis(tetrahydrofurane)(meso-tetraphenylporphinato)iron(II) (bTHF FeTPP) is the only known six-coordinate high-spin Fe(II) complex. Its THF ligands are rather loosely bound. Crystals slowly lose THF when exposed to the atmosphere, while the iron is five-coordinate in a solution in benzene (Reed et al. 1980). The magnetic susceptibilty of bTHF FeTPP is temperature dependent (Lecomte et al. 1986) and the axial Fe—O bonds shrink on cooling from 1.35 A at ambient temperature to 1.29 A at nitrogen temperature. 

Nitrile lassen sich mittels Niobium(IV)-chlorid-Bis-tetrahydrofuran/Tributylstannan in Thiolan reduktiv zu vicinalen Diaminen kuppeln1. Die Ausbeuten sind dabei im allge-meinen etwas geringer als bei der vorgenannten, von N-Silyl-iminen ausgehenden Me-thode. 

F. BIS(TETRAHYDROFURAN)-l,2-BIS(2-HYDROXY-3,5-BIS (fcrf-BUTYL)BENZYLIDENEIMINO)ETHANEALUMINUM TETRAPHENYLBORATE, [Al( BuSalen)(THF)2][BPh4]... 

TRIS(TRIMETHYLSILYL)SILYL LITHIUM TRIS(TETRAHYDROFURAN), LITHIUM TRIS(TRIMETHYLSILYL)SILYLTELLUROLATE BIS(TETRAHYDROFURAN), AND TRIS(TRIMETHYLSILYL)SILYLTELLUROL ... 

The systematic names for these compounds are lithium 1,1,1,3,3,3-hexamethyl-2-(trimethyl-silyl)-2-trisilanetellurolate-bis(tetrahydrofuran) and 1,1,1,3,3,3-hexamethyl-2-(trimethylsilyl)-2-trisilanetellurol. 

Lithium tris(trimethylsilyl)silyltellurolate bis(tetrahydrofuran) is a pale yellow, air-sensitive solid that is soluble in hydrocarbons, diethyl ether, and THF. The finely powdered solid oxidizes (sometimes pyrophorically) in air to give the dark green ditelluride (SiMe3)3SiTeTeSi(SiMe3)3.8 The lithium tellu-rolate is dimeric in the solid state as shown by X-ray crystallography10... 

Li02Si4TeC)7H43, Lithium, [l,l,l,3,3,3-hexamethyl-2-(trimethylsilyl)-2-trisilanetellurolato]bis(tetrahydrofuran)-, [152758-18-4], 31 164... 

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