Attempted preparation

Thiophene is also readily acylated under both Friedel-Crafts and Vilsmeier-Haack conditions and similarly to pyrrole and furan gives 2-acylated products. An almost quantitative conversion of thiophene into its 2-benzoyl derivative is obtained by reaction with 2-benzoyloxypyridine and trifluoroacetic acid. The attempted preparation of 2-benzoylthiophene under standard Friedel-Crafts conditions, however, failed (80S139). 

A formal ring enlargement of diazirines to five-membered rings is also observed with some hydrazones of ketodiazirines (65CB2509). On attempted preparation of hydrazones (201) from ketodiazirine (200) at 0 C the diazo compounds (202) are plausible intermediates since their transformation to aminotriazoles (203) is known. 

Benzamidomethyl-A -methylcysteine has been prepared as a crystalline derivative (H0CH2NHC0C6H 5, anhydr. CF3CO2H, 25°, 45 min, 88% yield as the tri-fluoroacetate salt) and cleaved (100% yield) by treatment with mercury(II) acetate (pH 4, 25°, 1 h) followed by hydrogen sulfide. Attempted preparation of S-acetamidomethyl-N-methylcysteine resulted in noncrystalline material, shown by TLC to be a mixture. ... 

In the ring-closure reaction of a-acylaminoketones with hydrazines, some dihydro-1,2,4-triazines were obtained. The possible 1,2-, 2,3-, or 5,6-dihydro structures were excluded by IR spectroscopic studies however, this method, as well as the attempted preparation of fixed derivatives, failed to distinguish between... 

However, IR and NMR spectral data indicated beyond doubt that the product isolated by these authors, even on lowering the temperature of esterification to — 70°, was allyl trichloromethyl sulfoxide (8a) and not allyl trichloromethanesulfenate (7a) as claimed4,0. This observation indicates that the initially formed ester undergoes spontaneous rearrangement to sulfoxide. Similarly, the attempted preparation of a,a-dimethylallyl trichloromethanesulfenate (7b) afforded y, y-dimethylallyl trichloromethyl sulfoxide (8b), thus proving the occurrence of a simultaneous 1,3-allylic shift. 

However, the pseudo-borole 95 stemmed from another reaction of 96. Unknown to the earlier researchers who reported the synthesis of 95,94 their attempted preparation of 96 instead gave partly 98, a rearrangement observed previously,95 whereupon the reaction of 98 with PhBCl2 yielded phenyl(bis(2,3,4-triphenyl-l-naphthyl)borane, the actual identity of pseudo-borole 95 (Eq. 31). 

Use of lumps of the solid aluminate, rather than its ethereal solution, and of peroxide-containing etherate [1], rather than the peroxide-free material specified [2], caused an explosion during the attempted preparation of diborane. 

Dining attempted preparation of trimethyl orthoformate, addition of sodium to an inadequately cooled chloroform-methanol mixture caused a violent explosion. See Ethanol (or methanol), Potassium sulfide, above See Sodium methoxide, below... 

The later publication [1] reveals that the title compound is in fact a relatively stable compound. The previously attempted preparation of the then unknown compound from trichloroacetonitrile, sodium azide and ammonium chloride (0.14 0.42 0.2 mol) by an analogous established method [2], but at lower initial temperature because of the exothermic reaction, gave, after vacuum evaporation of solvent, an oily product. When sampled with a pipette, this evolved gas and then exploded violently. It was thought that an azidomethyltetrazole may have been formed by displacement of chloro-substituent(s) by the excess azide employed [3], An alternative hypothesis which involved isomerisation of the title compound to the open chain azidoazomethine [4] was discounted, because no trace of this could be detected [1]. 

During the attempted preparation of 3-/i-chlorophcnylbutanoic acid by addition of the ketone (2 g mol) to peracetic acid (50%) in acetic acid at 65-70°C, a serious explosion occurred. 

Kennett, F. A. et al., J. Chem. Soc., Dalton Trans., 1982, 851-857 In attempted preparation of poly(selenium nitride), the black solid formed by interaction with selenium tetrabromide in acetonitrile exploded violently within 1 min at 0°C. The solid produced from diselenium tetrachloride in acetonitrile exploded at around 100°C, and in dichloromethane the product exploded in contact with a nickel spatula. 

Podophyllotoxin enolate tetrahydropyranyl ether Glinski, M. B. et al., J. Org. Chem., 1987, 53, 2749-2753 Attempted preparation of 2-fluoropodophyllotoxin by treatment of the tetrahydropyranyl ether with perchloryl fluoride led to a violent explosion. 

Reaction with water is vigorous, and with large amounts of peroxide it may be explosive. Contact of the peroxide with combustibles and traces of water may cause ignition [1], Violent explosions on two occasions during attempted preparation of oxygen were attributed to traces of sodium in the peroxide. The former would liberate hydrogen and ignite the detonable mixture [2,3],... 

Fused octahydrocycl[3.2.2]azines of the type 392 are obtained by tandem cycloadditions of pyridinium phenacylide with iV-substituted maleimides <1989JOC420>, and other types of fused octahydrocyclazines, viz. 394, result from the attempted preparation of the enamines 393, since these are unstable and undergo intramolecular acylation <1999T1763> (Scheme 114). 

Simple transition metal halides react cleanly with alkali metal boratabenzenes. In this way sandwich-type complexes 32 of V (27), Cr (64), Fe (58), Ru (61), and Os (61) have been made. The corresponding nickel complexes seem to be nonexistent, quite in contrast to NiCp2 in attempted preparations, mixtures of diamagnetic C—C linked dimers were obtained (29). In the manganese case, high sensitivity to air and water has precluded preparative success until now. Some organometallic halides have added further variations to the main theme. The complexes 33 of Rh and 34 of Pt were obtained from [(COD)RhCl]2 and [Me3PtI]4, respectively (61). 

Syntheses of the BA 3,4- and 8,9-dihydrodiols through reduction of the corresponding quinones with NaBH, (Figure 4) has been reported by Oesch (22,23). Attempted preparation of BA 1,2-dihydro-... 

The lability of the xanthato moiety may sometimes result in unpredictable dealkylation. Thus, in attempted preparation of palladium(II) and platinum(II)... 

Solid adducts between (C43) and (C6H5)2C=NH BF3 is sufficiently stable to withstand vacuum sublimation at 120 °C. Attempted preparation of corresponding BC13 derivatives led only to (diphenyl-methyleneimino)boranes 41). Recently, additional imine-trifluoroborane adducts have been described 44h they are listed in Table 8. 

Early syntheses of haloindoles involved direct reactions of indoles with chlorine, bromine, or iodine. In some cases, this approach was reasonably successful, but the instability of the resulting 3-haloindoles made product isolation and further chemistry difficult. For example, although attempted preparations of 3-chloro-, 3-bromo-, and 3-iodoindole were described in the early 1900 s [2], only recently have practical syntheses of these compounds and their N-protected derivatives become available. For example, 3-bromoindole (2) can be prepared in... 

Attempted preparation of the aldehyde precursor of the five-membered ether product through oxidation of the corresponding alcohol led not to the aldehyde, but instead the cyclic ether itself (Eq. 9.104). Evidently the cyclization reaction is facile in this case. 

The activating effect of the azide makes the fluorine labile, so that there is a risk of excess azide incorporation when attempting preparation by nucleophilic substitution of bromofluorocarboxylates, giving more explosive products than anticipated. 

The first attempted preparation of elemental Es was made on the 1-fig scale by distilling Li metal in vacuo onto an unheated sample of EsFj (Section II,A), followed by quickly raising the temperature of the Li-... 

Group IVA Donor Ligands. The anomalous reactions of PhaSiCl with metal carbonyl anions are discussed on p. 180. Only in the case of [Co(CO)3PPh3] was the normal substitution product obtained. GeH3Br reacts with Na-[Co(CO)4] in ether to produce [H3GeCo(CO)4]. The trideuterio-compound has also been prepared and spectroscopic properties reported for both compounds. The preparation and attempted preparation of halogen-bridged Ge-M compounds is referred to on pp. 180 and 200. In the case of cobalt. 

Advances in the chemistry of [M(CN)5L]" complexes, for M = Fe, Ru, and Os, have been reviewed.There has been rather little activity in the preparation of novel complexes, but considerable activity in studying the properties, especially solvatochromism and various aspects of kinetics of substitution, of known complexes. However there has been an attempted preparation of [Fe(CN)5(Ci2H25NH2)], in the hope of generating micelles or lyotropic liquid crystals. This preparation appeared to yield [Fe(CN)4(H20)(Ci2H25NH2)], whose alkali metal salts gave a hexagonal mesophase in water, but were also readily hydrolyzed to [Fe(CN)4(H20)2] . Heterobinuclear complexes of the form [(NC)5FeL ML 5] " " have been much studied, especially in relation to intramolecular electron transfer (see Section 5.4.2.2.5). 

The similar addition of a mesityl-substituted isocyanate to 1-morpiiolino-cyclohexene gave the dihydrothiazinone 233, which is in ring-chain equilibrium with 234. In the attempted preparation of the rerr-butyl-substituted derivative, the tetrahydrobenzothiazinone 235 was formed by loss of morpholine (81CB549). 

Addition of methanol onto 2 sometimes even occurs spontaneously upon attempted preparation of 2 [15bj. Under alkoxide catalysis, such alcohol additions... 

Compounds of type 94 with substituted and spirocyclopropane-annelated cyclopropane rings showed an increased rate of rearrangement, and the corresponding dimethyl-substituted starting material 94 k was never isolated, its transformation into 109k proceeded even in the absence of Lil upon attempted preparation (36% yield). This isomerization apparently occurs regioselectively and ste-... 

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