Pyridine/pentane

Oxalamidinate anions represent the most simple type of bis(amidinate) ligands in which two amidinate units are directly connected via a central C-C bond. Oxalamidinate complexes of d-transition metals have recently received increasing attention for their efficient catalytic activity in olefin polymerization reactions. Almost all the oxalamidinate ligands have been synthesized by deprotonation of the corresponding oxalic amidines [pathway (a) in Scheme 190]. More recently, it was found that carbodiimides, RN = C=NR, can be reductively coupled with metallic lithium into the oxalamidinate dianions [(RN)2C-C(NR)2] [route (c)J which are clearly useful for the preparation of dinuclear oxalamidinate complexes. The lithium complex obtained this way from N,N -di(p-tolyl)carbodiimide was crystallized from pyridine/pentane and... 

Despite its fleetingness, 78 has been captured by CO in a matrix at 10 K, affording low yields of ketene." Modarelli and Platz were unable to observe the formation of a pyridine ylide upon LFP generation of 78 in pyridine/pentane at —40°C. However, with perdeuterated methylcarbene (78- 4) a weak pyridine ylide signal was detected, and the rate constant of the 1,2-D shift could be estimated as ito 2 x 109 s-1 (r 0.5 ns) using a Stem-Volmer analysis (see Eqs. 3-6 in Section II).89 The activation energy for this 1,2-D shift was estimated at 2.3 kcal/mol, assuming A 1011 s-1.89 However, it seems likely that both 2sa and A are somewhat lower, with A 108 to 109 s (AS = —17 e.u.).89... 

Data for Dioxane/Pentane and Pyridine/Pentane (Alnmina)... 

Treatment with acetic anhydride and pyridine at room temperature followed by recrystallization of the crude product from chloroform-pentane gives the 3-acetate of (83a) mp 277-279° [aj —101° (dioxane). 

Pyridine-2,6-dicarbonitrile 1-oxide (500 mg, 3.45 mmol) in CH2C12 (500 mL) was irradiated for 10 h with a high-pressure 450-W Hanovia Hg lamp. The solution was evaporated under reduced pressure and the residue was extracted several times with pentane. The combined extracts were concentrated and the residue was repeatedly recrystallized (pentane) to give yellow needles yield 150mg (30%) mp 61-63 C (dec.). 

A mixture of PcSi(OH)2 (0.75 g, 1.3 mmol), chlorotrihexylsilane (5.0 mL), and anhyd pyridine (75 mL) was refluxed for 5 h. After the solution obtained had been allowed to cool, it was filtered and concentrated under vacuum. The resulting oil was mixed with pentane (10 mL) and the slurry formed was filtered. The solid was washed with pentane (10 mL) and acetone/H20, vacuum dried, and weighed (0.78 g). To recover additional product, the pentane filtrates were combined, concentrated, and filtered. The solid was washed and vacuum dried. The combined solids were chromatographed (alumina, toluene/hexane 1 2) yield 0.28 g (78%). 

Optimal pre-organization of the y-peptide backbone towards the formation of open-chain turn-like motifs is promoted by unlike-y " -amino acid residues. This design principle can be rationalized by examination of the two conformers free of syn-pentane interaction (f and II", Fig. 2.34). Tetrapeptide 150 built from homo-chiral unlike-y -amino acid building blocks 128e has been shown by NMR experiments in pyridine to adopt a reverse turn-like structure stabilized by a 14-mem-bered H-bond pseudocycle [202] (Fig. 2.37 A). 

Further investigations revealed that this hydrogenation is accelerated in pentane solution. These results are shown in brackets in Table 3 [31]. Under optimized reaction conditions high catalyst TOF up to 5,300 were achieved when 10 was used. In the absence of both hydrogen and nitrogen, 10 was converted into the q -arene complexes such as the bis(imino)pyridine iron q -phenyl complex, 10-Phenyl, and the corresponding q -2,6-diisopropylphenyl complex, 10-Aryl, in the 85 15 ratio in... 

The monoketone bis(2,2, /V,/V -bipyridyl)ketone forms a [CoinL2]+ complex on reaction with [Co(NH3)4(C03)]+ in water.981 As reported for a quite different Co11 complex, the ketone is hydrated to form the gem diol which binds as a monodeprotonated O-donor along with the two pyridine groups in a tridentate chelate, with very little distortion from octahedral observed in the complex. This appears to represent a facile route for this type of inherently poor donor to achieve coordination. Chelated /3-diketonate anions are long-studied examples of O-donor chelates, and continue to be examined. A simple example is the m-[Co(acac)2(NH 3)2]1 (acac = 2,4-pentane-dionate), structurally characterized and utilized to produce molecular mechanics force field parameters for /3-diketones bound to Co111.982... 

A variety of metals have now been investigated in our laboratory including Fe, Co, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, In, Ge, Sn, and Pb. Solvents employed have been acetone, ethanol, THF, diethylether, dimethylsulfoxide, dimethylformamide, pyridine, triethylamine, ispropanol, isopropanol-acetone, toluene, pentane, and water. Acetone-Au will be discussed in detail herein, along with Ag. 

In pentane, the distribution of 1,3-insertion product 25 to 1,2-Me shift product 26 is 91 9. Upon addition of 2-methyl-1-butene, the yield of 25 smoothly decreases (to 19% with 4 M alkene), but the yield of 26 is unaffected 1 Moreover, correlation of addn/l,3-CH insertion (to 25) for 18 is nicely linear. The simplest interpretation is that 25 comes directly from carbene 18, whereas the 1,2-Me shift product 26 comes from the excited diazirine.27 Interestingly, thermolysis of 24 at 79°C produces 90% of 25 and 10% of 26, but now the yields of both products smoothly decrease in the presence of an alkene. In thermolysis the (electronically) excited diazirine is unavailable, both 25 and 26 stem from the carbene, and their formation is suppressed by the alkene s interception of the carbene. A pyridine ylide kinetic study gave the 1,3-CH insertion rate constant (18 - 25) as 9.3 x 10s s"1.27-47... 

Pyridine ylide/LFP studies of 83-85 in pentane or isooctane afforded carbene lifetimes of 21-24 ns (k 4 to 5 x 107 s 1), similar to the lifetime of dimethylcarbene under these conditions. Unfortunately, these lifetimes are limited by reactions with the hydrocarbon solvents the lifetime of 83 is 1.5 times longer in cyclohexane-d12 than in cyclohexane. The observation that the lifetimes of 55-CI ( 1000 ns) and 55-F (—7000 ns) are considerably longer than those of 83 and 84 could reflect the superior stabilization provided by the halogen spectator substituents of 55, but this conclusion is tentative in the absence of definitive intramolecularly controlled lifetimes for 83-85. 

Add with stirring 22.5 g S0C12 in 100 ml ether in 20 ml portions to a solution of 15 g 3,5-dimethoxybenzyl alcohol, 1 ml pyridine and 200 ml ether. Let stand and wash with 2X100 ml cold water separate and dry, evaporate in vacuum the ether to get 16 g 3,5-dimethoxybenzyl chloride (I). Recrystallize from petroleum ether. 16 g (I), 300 ml ethanol, 30 g NaCN, 75 ml water reflux three hours and pour onto 400 g ice. After ice melts, filter and recrystallize precipitate from petroleum ether to get about 14 g 3,5-dimethoxybenzyl CN (II). 5 g 50% NaH in mineral oil wash three times with pentane or hexane fill flask with N2 or argon and add dimethoxyethane or dimethylformamide (freshly distilled from K if possible). Stir and add 9 ml methyl iodide. Carefully add 8 g (II) and stir twelve hours. Add ice water and neutralize with NaHC03 to pH 7-8. Extract with ether and dry, evaporate in vacuum the ether (can distill 170/0.1) to get about 9 g alpha, alpha-dimethyl-3,5-... 

The third procedure illustrated by this preparation involves the reaotion of ketones with trifluoromethanesulfonic anhydride in a solvent such as pentane, methylene chloride, or carbon tetrachloride and in the presence of a base such as pyridine, lutidine, or anhydrous sodium carbonate.7-11,15 This procedure, which presumably involves either acid-catalyzed or base-catalyzed enolization of the ketone followed by acylation of the enol with the acid anhydride, has also been used to prepare other vinyl sulfonate esters such as tosylates12 or methanesulfonates.13... 

Carbene the pentane- or heptane-insoluble material that is insoluble in benzene or toluene but which is soluble in carbon disulfide (or pyridine). 

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