Anils, formation

Amines tend to give more complex results. The compound obtained by treating a 5-halofuran-2-carboxaldehyde with aniline is now thought to have a structure resulting from anil formation, halogen displacement, protropy and protonation. The free base is too unstable to be studied easily but acetylation of the salt provides readily recognizable products.182 A related example is discussed later (Section X,A,2). 

The result of treating 5-bromofuran-2-carbaldehyde with aniline is more complex and a salt resulting from anil formation and bromide displacement is formed (70CB2992). 

Reaction CXLin. Condensation of Aromatic Aldehydes with Primary Aromatic Amines.—Anil formation takes place readily on heating. 

Anil formation from nitroso compound and 2,4,6-trinitrotoluene, 293 Anhydride, conversion to thioacid with HjS, 276... 

Anil formation can also be effected in alcoholic solution in the presence of catalytic amounts of sodium carbonate or piperidine the Schiff bases (usually deeply colored) are then precipitated and can be hydrolysed by acid in the usual way. 

Perform the followmg experiment with succinic anhydride. This illustrates the formation of an anilic acid, which is usually an excellent... 

Temperature control at -15° to -25°C was also required for maximum yield. The best results were obtained by maintaining a temperature of -20 to -25°C during the addition of citral anil to the acid and at -15°C for the duration of the reaction. At this temperature range, the formation of a-cyclocitral (III) is favored. Higher temperatures caused excessive polymer formation and favored formation of e-cyclocitral whereas lower temperatures caused a reduction 1n the yield of the citral mixture. At least part of the problem with the lower temperature reaction was the fact that the sulfuric acid tended to freeze around the inside of the reaction vessel causing the effective molar ratio of acid to anil to be reduced. These lower temperature reaction mixtures were also lighter in color which indicated less polymer formation but this was accompanied by a lower yield of cyclocitrals. 

Formation of the oxazole ring is not always the last step in synthesis of the brightener. Unsymmetrical compounds that contain both a benzoxazole group and an ethene linkage can be prepared by the anil synthesis [51], in which a compound possessing an activated methyl group reacts with a Schiff base. The preparation of brightener 11.31 is an illustration of this method (Scheme 11.12). 

A more complex reaction is involved in the cooligomerization of acetylenes and tert-butyl isocyanide using nickel acetate as the catalyst (Scheme 20)43 the nature of intermediate complexes leading to the formation of 2-cyano-5-terf-butylaminopyrroles has not been established. Cocyclization of tert-butyl isocyanide with coordinated hexafluoro-2-butyne gives rise to coordinated cyclopentadienone anils for molybdenum systems,44 hence the nature of acetylene substitutents and of the organometallic catalyst play crucial roles in these processes. The pyrrole products from the former reaction can be decomposed by sulfuric acid and the overall sequence provides a simple synthesis of 5-amino-2-cyanopyrroles (Scheme 20). 

Anilines are converted into nitrosoarenes ArNO by the action of hydrogen peroxide in the presence of [Mo(0)(02)2(H20) (HMPA)]224, whereas catalysis of the reaction by titanium silicate and zeolites results in the formation of azoxybenzenes ArN (0)=NAr225. Azo compounds ArN=NAr are formed in 42-99% yields by the phase-transfer assisted potassium permanganate oxidation of primary aromatic amines in aqueous benzene containing a little tetrabutylammonium bromide226. The reaction of arylamines with chromyl chloride gives solid adducts which, on hydrolysis, yield mixtures of azo compounds, p-benzoquinone and p-benzoquinone anils 234227. 

The pyridinium chlorochromate (PCC) oxidations of pentaamine cobalt(III)-bound and unbound mandelic and lactic acids have been studied and found to proceed at similar rates.Free-energy relationships in the oxidation of aromatic anils by PCC have been studied. Solvent effects in the oxidation of methionine by PCC and pyridinium bromochromate (PBC) have been investigated the reaction leads to the formation of the corresponding sulfoxide and mechanisms have been proposed. The major product of the acid-catalysed oxidation of a range of diols by PBC is the hydroxyaldehyde. The reaction is first order with respect to the diol and exhibits a substantial primary kinetic isotope effect. Proposed acid-dependent and acid-independent mechanisms involve the rapid formation of a chromate ester in a pre-equilibrium step, followed by rate-determining hydride ion transfer via a cyclic intermediate. PBC oxidation of thio acids has been studied. ... 

Although JV-methylisatin and 143 in ethanol gives the expected anil,412 reaction in acid can give 144 and 145.412 A mechanism analogous to the Stevens rearrangement is proposed for the formation of 145. 

Budgeting. Changes in the storage and retrieval of chemical information require that libraries anil information centers now consider not only what should be purchased but also what monies should be allocated for the purchase of information in nonprint formats such as CD-ROMs (compact disk read-only memory and on-line databases. Coupled with this is budgeting for the cost of hardware and software to enable the rapid and cost-effective delivery of needed information. The geometric increase in sources, both printed and on-line, has increased ihe role of the information specialist as an expert in the delivery of chemical information. Retrieval from increasingly diverse and complex sources becomes the paramount issue for searchers of chemical literature in the 1990s. 

A solution of 200 g. (3.5 moles) of potassium hydroxide in 200 cc. of water is placed in a 2-1. flask fitted with a reflux condenser. The mixture is heated to about 8o° and 202 g. (r mole) of isopropylmalonic ester (Note 1) is added through the condenser over a period of about one hour. The mixture should be shaken well to prevent the formation of two layers. The saponification proceeds rapidly forming a clear solution. The solution is transferred to a 20-cm. evaporating dish, the flask is rinsed with 50 cc. of water, and the solution anil washings are evaporated practically to dryness on a steam bath (Note 2). 

Certain aromatic imines undergo a similar cyclodehydrogenation to the phenanthridine. Benzylideneaniline (330) yields phenanthridine (331) only in sulfuric acid,355 whereas diphenylmethyleneaniline cyclizes in the presence of oxygen or iodine.356 Cyclizations have also been reported in Schiff s bases formed from a- and /J-naphthylamine357 and from 4-aminoquinoline,358 and in the mesomeric betaine 4,5-diphenyl-2-mercapto-l,3,4-thiadiazolium hydroxide.359 Irradiation of the anil of 2-aminonaphthalene (332) in ethanol, however, leads to incorporation of ethanol and the formation of 3-phenylbenzo[/]-quinoline (333).860 Additional photoproducts are obtained when the photolysis is carried out in w-hexanol.361... 

That reaction occurs with potassium hydroxide is surprising, as it was previously suggested by Becker8 that the success of the synthesis with anils as opposed to the use of the corresponding aldehydes was due to the anhydrous conditions resulting from formation of aniline instead of water during the reaction. 

The stereochemical course of the Anil Synthesis is such that exclusive formation of trans products has been observed.11 This can be explained by consideration of the conformations of the intermediate addition product. The Newman projections (lOa-c) represent the three possible extreme conformations, and it can be seen that 10a, being the least sterically hindered, would be expected to be the most energetically... 

Further styryl and stilbenyl derivatives from 90 and 91 are shown in Table VII. Also reaction of these two compounds with heteroaromatic anils, such as that derived from 3-formyldibenzofuran and p-chloro-aniline, leads to the formation of the styryl and ethylene compounds 94 and 95, respectively.54... 

From the field of six-membered sulfur Containing heterocycles, it has been shown that 2,8-dimethylphenoxathiin (122) and also 2,7-dimethyl-thianthrene (123) undergo reaction with anils, as exemplified by the formation of the respective distyryl derivatives 124 and 125 on treatment with benzalaniline.26... 

The formation of styryl pyridines by condensation of anils with picolines was first reported by Crippa and Maffei.79 80 These workers found that 2-picoIine ethiodide (180) reacted with benzalaniline in methanol in the presence of piperidine to give 2-styrylpyridine ethiodide (181). However, it was also reported that 3-picoline ethiodide and 2-picoline itself failed to react under these conditions. 

The formation of anils 129 occurs in accordance with the generally accepted mechanism for thermal rearrangements of aliphatic azides to imines which involves nitrenes 127 as the intermediate (74JA480). Ni-trenes may undergo cyclization to aziridines 105 [cf. Section I1I,C,1 (Scheme 6) and Section lII,C,4,b(ii)] which are converted into ben-... 

The kinetics of chromium(l 11 )-catalyscd oxidation of fonnic acid by Ce(TV) in aqueous H2SO4 can be rationalized in terms of initial formation of an outer-sphere complex involving oxidant, catalyst, and substrate (S), Ce(TV)(S)Cr(III), followed by an inner-sphere complex Ce(III)(S)Cr(IV). It is proposed that electron transfer occurs within this complex from substrate to Cr(TV) (with elimination of H+) followed by fast reaction to give CO2 (again with elimination of H+).54 In contrast, there was no kinetic evidence for the accumulation of a corresponding inner-sphere intermediate in the osmium(VIII)-catalysed Ce(TV) oxidation of DMSO to dimethyl sulfone here, the observed rate law was rationalized in terms of rate-determining bimolecular electron transfer from DMSO to Os(VHI) in an outer-sphere step.55 The kinetics of oxidation of 2-hydroxy-l-naphthalidene anil by cerium(IV) in aqueous sulfuric acid have been... 

This is an example of the Doebner synthesis of quinoline-4-carboxylic acids (cin-choninic acids), which consists of the condensation of a primary aromatic amine with pyruvic acid and an aldehyde. The mechanism is probably similar to the synthesis of quinolines discussed above and involves the intermediate formation of a dihydroquinoline derivative, which is subsequently dehydrogenated by the anils derived from the aromatic amine and the aldehyde. 

---