3.5- di-r-butyl

Gol dfarb and Kondakova obtained, by hydrolysis of 2,5-di-r-butyl-3,4-bischloromethylthiophene (125), a product with m.p. 220°-221°, first thought to be 4,6-di-r-butyl-li/,3ff-thieno[3,4-c]furan. However, NMR and IR spectra and molecular weight measurements demonstrated later l,3,7,9-tetra-l-butyl-4i/,6//,10i/,12i/-dithieno[3,4-c 3, 4 -/i](l,6]-dioxecin (126) structure [Eq. (39)]. 

Unsubstituted 3-hydroxythiophene is less stable than 2-hydroxythiophene (63AHC(l)l). This instability may be due to oxidative coupling. In order to confirm this, 2,5-dimethyl-3-hydroxythiophene was subjected to ferricyanide oxidation (72ACS31). Racemic and meso forms of 2,2, 5,5 -tetramethyl-bi-4-thiolen-3-one (445) were isolated. When the a-substituent was r-butyl instead of methyl, exposure to air gave 2-(2,5-di-r-butyl-4-thiolen-3-one) 3-(2,5-di-r-butylthienyl) ether (446), formed by carbon-oxygen coupling. 

A catalytic, completely regioselective conversion of 4,4-dimethyl-2-pentyne (methyl-r-butylacetylene) to 2,5-di(r-butyl)-3,4-dimethylcyclopentadienone is mediated by (PhCN)2PdCl2. Other examples exist for early as well as late transition metals, and an isonitrile has been used as a CO equivalent in one Ni -based system as well, Finally, a heterogeneous catalytic intramolecular cycloaddition of diynes has been developed, leading to cyclopentadienones which either dimerize (Diels-Alder) or in certain cases may be trapped by nucleophiles (equation 10). °... 

Reduction of CpTi(OAr)Cl2 (OAr = 2,3,5,6-tetraphenyl-phenoxide) with 2 equivalent of sodium amalgam at room temperature in the presence of Me3C=CH gives the 2,5-di(r-butyl)titanacyclopentadiene complex, Cp(ArO)Ti(2,5-t-BU2-C4H2). When Cp(ArO)Ti(2,5-r-Bu2-C4H2) is heated at 100 °C for a few days in CgDg it isomerizes to the more stable 2,4-di(r-butyl) regioisomer. ... 

Alkylation occurs readily, but is rarely of preparative use the efficient 2,5-di-r-butylation of thiophene is one such example. ... 

Anhydrous HCl rapidly bubbled through a soln. of 3-bromo-2,5-di-/ r/-butyl-1,4-benzoquinone in glacial acetic acid during 1 hr., and the intermediate quinol oxidized with N2O4 in chloroform -> 2-diloro-3-bromo-5-tert-butyl-l,4-benzo-quinone. Y 75%. F. e. s. H. W. Moore et al., J. Org. Chem. 57, 1984 (1972). 

Cobalt complex 83 was obtained by the reaction of [CpCo(SMe2)3]2(BF4)2 withpentamethylpyrrole [88AG(E)579]. Full cobalt sandwich of 2,5-di- r butyl-pyrrole is also known [91 JCS(CC)1368]. Meanwhile, attempts to synthesize other pyrrolyl complexes of cobalt, (r -2,5-dimethylpyrrole)cobalttricarbonyl and the 3,4-dimethyl analog, have been unsuccessful [87JOM(330)231]. 

Cp3S03Me, CH2CI2, Pyr, 80°, 2.5 h, 85-90% yield.The use of 2,6-di-r-butyl-4-methylpyridine as a base is also very effective. ... 

The base-stabilized germanimine (Me2Si)2(N-t-Bu)4Ge=N(SiMe3) does not react with benzophenone, even upon heating.72 Apparently, no other reactions between stable germanimines and simple carbonyl compounds have been investigated however, the reaction with a diketone, 3,5-di-r-butyl-ort/io-quinone, has. Both a [2 + 2] and a [2 + 4] cycloaddition reaction have been postulated the initially formed adducts are unstable and decompose (see Scheme 4). 

Sensitized photoaddition of singlet oxygen to 3,5-di-r-butyl-1 -ethoxycarbonyl-1//-azepine, which is known to give a [6+2]ir adduct with TONE, was also investigated. However, in this instance only the [4+2]ir adduct (162 R = Bu ) is isolated, which on heating at 170 °C undergoes an unusual rearrangement to the epoxy-epioxide (165) in 95% yield. 

Steroid side chain.1 The key step in a method for stereocontrolled addition of the side chain to 17-kelo steroids is hydroboration of a 17(20)-(Z)-ethylidene steroid (I), which proceeds selectively to give 2, with the desired natural configuration at C,- and C2ft. The product reacts with most alkylating reagents in rather low yield, possibly because of stcric factors however alkylation with the anion of chloroacetonitrile (potassium 2,6-di-r-butyl-4-methylphenoxide) in T1IF gives the nitrile 3 in 60 70% yield. One added attraction of this route is that 9-BBN reacts preferentially with a 17(20)-double bond in the presence of a 5(6 )-double bond. 

Silica gel is an effective catalyst for the t-butylation of thiophene and benzo[/ ]thiophene using t-butyl bromide. 2,5-Di-r-butylthiophene and 3-f-butylbenzo[b]thiophene can be prepared easily by this procedure (84JOC4161). Alkylation of thiophene with f-butyl chloride, isopropyl chloride or ethyl chloride at - 70°C in the presence of A1C13 produced a-complexes under kinetic control. On thermal equilibration, migration of alkyl from position 3 to position 2, as well as disproportionation to dialkyl-and trialkyl thiophenes can occur (86T759). 

Di-f-butyl-3,6-dineopentylthieno[3,2b]thiophene (338) was obtained unexpectedly by the phosphite desulfurization of 4-r-butyl-5-neopentyl-l,3-dithiole-2-thione (337 Scheme 117). The alternate structure (339) was ruled out on the basis of an X-ray analysis (75UP31800). 

The homoleptic complex tris(2,4-di- r/-butyl-lA3,3A3-diphosphete) Mo 5 was obtained by reacting fac-(CO)3(MeCN)3Mo] with P-alkyne 44a <2002AGE4047>. The compound exhibits a unique temperature-dependent, reversible P-G bond formation between two of the heterocycles in the solid state. A related close contact between a P-atom of one Jt-coordinated lA3,3A3-diphosphete ligand and a C-atom of another one at the same metal center has also been observed for the tungsten analogue of 5 <2000TH1>. 

J,3-DimethyI-2,4-di-r-butyl-l,3,2,4-diazadiphosphetidine 2-TeUuride2 16 ml of benzene arc cooled in an ice/water bath and 1.2 g (5.12 mmol) of 1,3-dimcthyl-2,4-di-/-butyl-1,3,2,4-diazadiphosphctidinc together with0.67 g(5.25 mmol) oftellurium powder are added. The mixture is stirredat 20° for 3 h, filtered through a glass frit to remove unreacted tellurium, and the solvent is removed from the filtrate under reduced pressure. The residue is dried under oil-pump vacuum yield 1.8 g (100%) m.p. 83-90°. 

Triphenylstannyl-3,5-di( r/-butyl)-1,2,4-triphosphole with Co2(CO)8 gives the /7 -coordinated species 169 (010M2905). The latter enters into photochemical CO-substitution reactions with triethyl- and triphenylpho-sphine one carbonyl ligand is substituted. With cyclohexylcyanide, however, a mixture of two substitution products is formed, with one and two CO ligands being substituted by CN-Cy groups, respectively. 

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