4-Amino-o-xylene

Synonyms 1-Amino-3,4-dimethylbenzene 4-Amino-o-toluene 3-Amino-o-xylene Aniline,... 

Chloronicotinic acid, when heated gradually to 145 vinth methyl o>aminobenzoate and potassium iodide, gives lX-162 with 3-amino-o-xylene, however, the 2-anilmonicotinic acid derivative (IX-163) is obtained. When a... 

Nitroxylenes are especially important because 4-amino-o-xylene (xylidine), formed from 4-nitro-o-xylene (4-o-NX) upon reduction, is used as a starting material for the production of riboflavin. Nitration of o-xylene by the conventional mixed acid method gives a mixture of 4-o-NX 31-55% and 3-o-NX 45-69 %. 

Starting with 3-nitro-o-xylene (28), 3-(2-methyl-6-nitrophenyl)-4,5-dihydro-isoxazole (31) is synthesized via the benzaldehyde oxime 29. Subsequent reduction of the nitro group, replacement of the corresponding amino group by methyl... 

In a recent modification of the second synthesis (50S) effected for fluvibactin (45) an o-xylene protection group was proposed (reaction of 2,3-dihydroxy-benzoic acid methyl ester with 1,2-di(bromomethyl)benzene) which could be removed later by hydrogenolysis. The formation of the oxazoline ring from protected DHB-L-threonine methyl ester was achieved with Mo(VI) catalysts (e.g. (NH4)2Mo04) without affecting the chiral centers. Derivatization of the primary amino groups of norspermidine with the protected DHB methyl ester was catalyzed by Sb(OC2115)3. 

The catalytic and chiral efficiency of (S,S)-le was also appreciated in the asymmetric synthesis of isoquinoline derivatives, which are important conformationally constrained a-amino acids. Treatment of 2 with a,a -dibromo-o-xylene under liquid-liquid phase-transfer conditions in the presence of (S,S)-le showed complete consumption ofthe starting Schiffbase. Imine hydrolysis and subsequent treatment with an excess amount of NaHCOs facilitated intramolecular ring closure to give 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid tert-butyl ester 38 in 82% yield with 98% ee. A variety of l,2,3,4-tetrahydroisoquinoline-3-carboxylic acid derivatives possessing different aromatic substituents, such as 39 and 40, can be conveniently prepared in a similar manner, with excellent enantioselectivity (Scheme 5.20) [25]. 

While cycloaddition approaches have been discussed extensively in this chapter, there are certain substitution patterns that are not amendable to such approaches. In these cases, the more traditional annelative approaches are necessary. For example, the 5,6-dihydropyrrolo[3,4-rf]imidazol-4(3//)-one (286) is obtained from the diamine (285) and triethyl orthoformate. If formamide is used in excess, 6-(formamidomethylene)-5,6-dihydropyrrolo[3,4-d]imidazol-4(3//)-one (287) is obtained (Scheme 53) <70JPS1732>. A variant of the Thorpe cyclization was employed in the preparation of 3-amino-4//-pyrrolo[3,4-c]isoxazoles (289) from a-cyanooximes (288) (Equation (66)) <68JMC453>. 3-Acyltetramic acid (290 X = NR2) and 3-acyltetronic acid (292 X = O) hydrazones undergo ready cyclization in refluxing xylene with catalytic p-toluenesulfonic acid to afford 4-oxo-l,4-dihydro-6/f-pyrrolo[3,4-c]pyrazoles (291) and 4-oxo-l,4-dihydro-6//-furo[3,4-c]pyrazoles (293), respectively (Equation (67)) <82SC43l>. The novel synthesis of 5-amino-6a-hydroxydihydro-6//-pyrrolo[2,3-j]isoxazole (296) from 3,4-disubstituted 4-(amino)isoxazol-(4//)-ones (294) is hypothesized to occur by the cyclization of the ketene aminal intermediates (295) (Scheme 54) <91S127>. 

A solution of 5-amino-4-chloro-2,6,8-trimethylquinoline (0.22 g, 1 mmol) and 2,6-di-tert-butyl-4-aminophenol (0.35 g, 1.6 mmol) in o-xylene (5 ml) was refluxed for 3 h, then cooled to room temperature, diluted with chloroform (5-7 ml) containing 1 ml of saturated water solution of ammonia and allowed to stand... 

Co = Catechol oxidase He = Hemocyanin Tyr = Tyrosinase MePy2 = Al,Al-bis(2-pyridylethyl)methylamine TACN = l,3,5-triazocyclononane TMPA = Tris[(2-pyridyl) methyljamine XYL-O = Q ,Q -bis[Al,Al-bis(2-pyridylethyl) amino]-m-xylene-2-olate XYL = Q ,Q -bis[A, Al-bis(2-pyri-dylethyl)amino]-m-xylene XYL-R = Meta substituted a,a -bis[Al,Al-bis(2-pyridylethyl)amtno]-m-xylene N3 = N,N, Al -Tetrakis-(2-pyridin-2-yl-ethyl)-propane-1,2-diamine N4 = Al,Al,Al, Al -Tetrakis-(2-pyridin-2-yl-ethyl)-butane-1,2-diamine N5 = Al,Al,Al, Al -Tetrakis-(2-pyridin-2-yl-... 

SYNS l-AMINO-2,5-DIMETHYLBENZENE 3-AMINO-1.4-DIMETHYLBENZENE 2-AMINO-l,4-XYLENE 2,5-DIMETH LANILINE 2,5-DIMETHYL-BENZENAMINE 2,5-DIMETHYLPHEKYL3.MINE 5-METHYL-o-TOLL IDINE 6-METHYL-m-TOLUIDINE p-XYLIDINE pOT)... 

One-electron oxidation of aromatic compounds (ArH) leads primarily to corresponding radical cation which exist either in monomeric (ArH +) or dimeric form [(ArH)2 ] the latter usually formulated as r-dimer [70]. However, radical cations are reactive species and can undergo further reaction yielding more persistent radical cations e.g. oxidation of rert-butylbenzene or of toluene or o-xylene yielded radical cation of 4,4 -di-rerf-butyl biphenyl, 4,4 -bitoluene or 3,3, 4,4 -tetramethyl biphenyls, products of further a-coupling, proton loss and further one-electron oxidation [71]. This is a well-known pathway of biaryl dehydrodimerization, explored in anodic and metal-ion oxidation of ArH [72, 73]. Other compounds with high reactivity in (T-coupling are alkoxy and amino substituted ArH [73]. Thus a risk with characterization of radical cations is that hardy survivors and not primary radical... 

Dimethylaniline has been prepared by reduction of the corresponding nitro compound, either chemically or catalyti-cally. It has been prepared from 3,4-dimethylphenol by heating with ammonia, ammonium bromide, and zinc bromide from w-toluidine hydrochloride by alkylation with methanol at high temperatures from anhydro-4-amino-2-methylbenzyl alcohol by dry distillation from calcium hydroxide from 2-methyl-S-aminobenzyl alcohol by reduction with sodium from 2-methyl-5-nitrobenzyl chloride and 2-methyl-S-nitrobenzyl acetate by catalytic reduction from o-xylene by direct amination with hy-droxylamine hydrochloride in the presence of aluminum chloride and from 3,4-dimethylacetophenone by the Beckmann rearrangement of the oxime.i" The present method has been published. ... 

Scheme 6.186) [347]. The condensation of O-allylic and O-propargylic salicylalde-hydes with a-amino esters was carried out either in the absence of a solvent or - if both components were solids - in a minimal volume of xylene. All reactions performed under microwave conditions rapidly proceeded to completion within a few minutes and typically provided higher yields compared to the corresponding thermal protocols. In the case of intramolecular alkene cycloadditions, mixtures of hexa-hydrochromeno[4,3-b]pyrrole diastereoisomers were obtained, whereas transformations involving alkyne tethers provided chromeno[4,3-b]pyrroles directly after in situ oxidation with elemental sulfur (Scheme 6.186). Independent work by Pospisil and Potacek involved very similar transformations under strictly solvent-free conditions [348]. 

SYNS 1-AMINO-2.4-DIMETHYLBENZENE 4-AJMINO-l,3-DIMETHYLBENZENE 4-AMINO-3-METHYLTOLUENE 4-AMINO-l,3-XYLENE 2,4-DIMETHYLANILINE 2,4-DIMETHYLBENZENAMINE 2,4-DIMETHYLPHEiNYLAMINE 2-METHYL-p-TOLUIDINE 4-METHYL-o-TOLUIDINE 2,4-XYLIDENE (MAK) m-XYLIDINE m-4-XYLIDINE... 

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