Amino compounds, conversion

The pale yellow colour cannot be removed by redistiUation or recrystal lisation the coloured product probably contains some amino compound rendering it unsuitable for conversion into a Grignard reagent. A pure... 

A troublesome side reaction encountered ia the manufacture and use of amino resias is the conversion of formaldehyde to formic acid. Often the reaction mixture of amino compound and formaldehyde must be heated under alkaline conditions. This favors a Canni22aro reaction ia which two molecules of formaldehyde iateract to yield one molecule of methanol and one of formic acid. 

Following this pnblication, the anthors tested a series of Pd-NHC complexes (33-36) for the oxidative carbonylation of amino compounds (Scheme 9.8) [44,45]. These complexes catalysed the oxidative carbonylation of amino compounds selectively to the nreas with good conversion and very high TOFs. Unlike the Cu-NHC catalyst 38-X, the palladium complexes catalysed the oxidative carbonylation of a variety of aromatic amines. For example, 35 converted d-Me-C H -NH, d-Cl-C H -NH, 2,4-Me3-C H3-NH3, 2,6-Me3-C H3-NH3, and 4-Ac-C H3-NH3 to the corresponding nreas with very high TOFs (>6000) in 1 h at 150°C, in 99%, 87%, 85%, 72%, and 60% isolated yields, respectively (Pco,o2 = 3.2/0.8 MPa). 

The way in which aromatic amino compounds lead to the formation of MHb is of some interest in regard to the role played by the first reaction of the pentose phosphate cycle in this reaction system. It has been stated (L5) that nitrosobenzene effects within one hour the conversion of Hb to MHb to the extent of 80% of total pigment according to the following reactions ... 

In cases of some derivatives bearing an amino substituent, conversions to acylamines, alkylamines, and amidines have been reported. These substrate amines include the above-mentioned two amino compounds 157 and 159 as well as other compounds shown in Scheme 25. 

It has been established that the conversion of 2-chloro-4-phenylquinazo-line into 2-amino-4-phenylquinazoline by treatment with potassium amide/liquid ammonia also occurs with ring opening (74RTC227).This was proved by the experimental result that in the 2-amino compound obtained from 2-chloro-4-phenyl[3- N]quinazoline, about 70% of the label is present in the amino group, i.e., formation of 2-[ N-amino]-4-phenylquina-zoline (83) see Scheme 11.36. 

The reactions of 2,4,6-triphenyl-3-azapyrylium perchlorate (64) with various amino compounds were investigated in detail (Scheme 9) (81BCJ2387). Conversions into 3-phosphapyridines 65 and oxazepines 66 have been also described (74S187 87TL1093) (Scheme 9). 

The isolation of 5-formyl-2-methylpyrimidine (62) and 5-amino-2-methylpyrimidine (63) from thiamin requiring mutants of Neurospora has led to a suggestion that these may be late intermediates in the biosynthesis of (45), a contention supported in part by the demonstration of conversion of the amino compound (63) to the hydroxymethylpyrimidine (45) by yeast cell-free extracts. 

For the cine amination one would normally consider a mechanism involving the formation of thiophyne. However, several pieces of evidence lead to the rejection of the thiophyne mechanism among them, the marked dependence of product distribution on amide concentration, and the non-formation of aminated product in the reaction of 2-bromo-5-methylthiophene under the same conditions. A normal addition-elimination mechanism (2-bromo -> 3-bromo -> 3-amino) is also invalid since the conversion of 3-bromothiophene to 3-aminothiophene under the same conditions is 200 times slower than the conversion 6f 2-bromothiophene to the 3-amino compound. There is also no evidence from NMR of any initial adduct formation. Considering all these facts, the proposed mechanism (Scheme 164) for cine amination involves attack by amide ion at the /8-position of a di- or tri-bromothiophene to form an aminobromothiophene and subsequent debromination of this species. In support of this is cited the fact that the individual polybromothiophenes are converted to 3-aminothiophene by KNH2 in ammonia. Also, 4-amino-2-bromothiophene (485) has been isolated in the reaction of 2-bromothiophene with sodamide. 

Fluoroalkylamines react with nitrous acid to produce the corresponding unstable fluoroahphatic diazomum ions Placement of the tnfluoromethyl group at a carbon position a, (i, or y to a diazomum ion was used to probe the inductive effect on the chemistry of the transient carbocation resulting from dediazomation [7] If the fluoroalkyl group is bound to the same carbon as the amino group, conversion to the more stable diazo compound occurs For example, 4-diazo-l,l,l,2,2-pentafluoro-3-pentafluoroethyl-3-tnfluoromethylbutane is obtained from the reaction of the poly-fluoroalkylamine salt with sodium nitrite [8, 9] (equation 8)... 

The pale yellow colour cannot be removed by redistillation or recrystallisation the coloured product probably contains some amino compound rendering it unsuitable for conversion into a Grignard reagent. A pure white product may be obtained by the following procedure. Dissolve 50 g of the coloured compound in 200 ml of hexane and pass the solution through a column of activated alumina (80-200 mesh dimensions about 9 cm x 3 cm) wash the column with 750 ml of hexane. Remove the hexane by distillation 49 g of pure 2-bromonaphthalene, m.p. 58 °C, remains. This is sufficiently pure for use in Grignard reactions. 

Hodge7 has advanced several possible routes for the conversion of the enol form of the 1-amino-l-deoxy-2-ketose into melanoidin, and the evidence to support these mechanisms is considerable. Thus, the enol may be converted into the Schiff base of a furaldehyde, or to a reductone by loss of water. It may also be broken down into smaller fragments (for example, hydroxy-2-propanone or pyruvaldehyde), which react further with amino compounds. The enol may also react with an a-amino acid and be converted to an aldehyde by a Strecker degradation. The compounds thus formed from... 

The conversion of nitrocoumarins into the amino compounds has been achieved by hydrogen transfer (95JCR(S)372) and an intramolecular hydride transfer features in the formation of Mannich bases of 4-aminocoumarins from 4-alkylaminocoumarin-3-carbaldehyde (95S633). Amine derivatives of coumarin-3-carboxaldehyde undergo a thermal 1,3-cycloaddilion involving an oxime nitrone isomerisation on reaction with Al-methyl-hydtoxylamine yielding hetero-fused coumarins (95JCS(P1)1857). 

Dimethylaminothioxanthone 1,1-dioxide is reduced to the 9-amino compound 357 by conversion into the imine by ammonia in the presence of TiCb and subsequent reaction with NaBH4 (Equation 79) <2002JOC3585>. 

In many cases, the substrate to be subjected to asymmetric conversion is coupled to the carbohydrate via the anomeric position. For the synthesis of amino compounds, the substrate is linked to the carbohydrate as a derivative of a glycosyl-amine. After completion of the asymmetric synthesis the product can be detached from the carbohydrate auxiliary by acidic hydrolysis. In most cases auxiliary and product can be separated by extraction or recrystallization techniques, and the carbohydrate auxiliary readily regenerated from its recovered detachment derivative. 

Furopyrimidines undergo many of the reactions that the pyrrolopyrimidines do, although there are fewer examples. The conversion of the oxofuro[2,3-d]pyrimidine (39) to the (substituted)amino compound (40) with phosphorus pentoxide and a primary amine exemplifies the type of functional group interconversion which is possible (Equation (9)) <86CS337>. 

Azides are formed by the reaction of lithio derivatives with />-toliicncsulfonyl azide, and these in turn can be converted into the corresponding amino compounds by a variety of reductive procedures. Nitro compounds are available by a novel reversal of the general pattern of reaction with electrophiles. This approach requires the initial conversion of the lithio compound into an iodonium salt followed by reaction with nitrite ion. This is illustrated by the preparation of 3-nitrothiophene (Scheme 145). Other nucleophiles, such as thiocyanate ion which yields the 3-thiocyanate, can be employed. The preparative significance of these reactions is again that products not accessible by electrophilic substitution can be obtained. 

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