Amidines, diaryl

Reaction of 2-amino-5-aryl-thiadiazole (88 R = Ar) with aryl nitriles in the presence of aluminum chloride produced the aryl amidine (89) which was oxidized with lead tetraacetate to yield the 2,6-diaryl-[ 1,2,4]-triazolo[5,1 -( ]-1,3,4-thiadiazoles (90) <91 UC(B)435>. 

Werden anstelle von a-Halogen- oder a-Hydroxy-ketonen a-Halogen-carbonsaure-nitrile ein-gesetzt und ist die Amidin-Komponente N,N -Diary -substituiert, so erhalt man in guten Aus-beuten 4-Amino-l,3-diaryl-imidazolium-Salze113 z.B. ... 

Diaryl-l,2,3,5-oxathiadiazine 2,2-dioxides (187) are valuable starting reagents which are readily prepared by treatment of the aryl cyanide with sulfur trioxide. Amidines, imidates and trichloroacetonitrile react with (187) to give a wide range of 4,6-diaryl-l,3 5-triazines in 50-90% yields under acidic conditions (equation 108) (63CB2070). 

Patel and coworkers87"89 and others90 have been carrying out detailed investigations on the analytical applications of a number of amidines, e.g. JV-hydroxy-JV-phenyl-iV -benzylbenzamicline,91 JV.AT -diaryl substituted A-hydroxy-p-toluamidines87 and hydroxydiarylbenzamidines.88"90... 

Configuration of A. /V-disubstituted amidines is thus regularly E, reversed rather than in amidines with a free NH2 group which are Z95. Derivatives with only one substituent at the amino group are in the middle and their conformation may be sensitive to small steric effects. In 24 a tautomeric equilibrium would be degenerate, hence the problem is simplified. In the case of IV,-diaryl derivatives, three forms are possible (24a-c) the fourth would be very improbable for steric reasons. From dipole moments an equilibrium... 

A short synthesis of imidazoles 47 was discovered on the basis of the reaction of 3,5-diaryl-l,2,4-dithiazolium triiodides 46 (X = I3) with glycinates or aminoacetonitrile. Intermediate (thiocarbonyl)amidines 48 were oxidized in situ to 1,2,4-thiadiazolium salts 49 by the triiodide anion resulting in imidazoles 47. The same reaction with 3,5-diaryl-l,2,4-dithiazolium perchlorates 46 (X = C104) stops at the formation of amidines 48 due to the lack of an oxidizing counterion (Scheme 3) <1997JOC3480>. 

A new, simple, synthesis of 2,4-diaryl-l, 3,5-triazines is shown in Scheme 1. It arose from an attempt to obtain the pyrano[4,3-rf]pyrimidine system by reacting aryl amidines with the 3-methoxymethylenedihydropyran-2,4-dione (1 X= CH2). As well as the desired products, diaryl-I,2,3-triazines were obtained in 30-40% yield. The use of 5-methoxymethylene-2,2-dimethyl-l,3-dioxan-4,6-dione (1 X= 0)(derived from Meldrum s acid) gives the triazines in better yield (> 50%). It was also observed that 3-methoxymethylenefuran-2,4-dione reacted with 5-methylisothiouronium bromide to yield 2,4-bismethylthio-l,3,5-triazine [95M99]. 

Pinner triazine synthesis. Preparation of 2-hydroxy-4,6-diaryl-i-triazines by reaction of aryl amidines and phosgene. 

Amidines also react with carbonic acid derivatives to provide mixed substituted 1,3,5-triazines. Thus, treatment of aryl amidines, e.g. 3, with phosgene gives 4,6-diaryl-l,3,5-triaz.in-2-ols.318... 

Diaryl-6-substituted 1,3,5-triazines are obtained from reaction of a benzoxazonium cation with amidines and perchloric acid in acceptable yields (see Section 6.12.10.4). Aryl cyanates with... 

Diaryl-1,3,5-triazines 9 are obtained from 5-methoxymethylene-2,2-dimethyl-l,3-dioxane-4,6-dione 6 (easily accessible from Meldrum s acid, p 386) by sequential reaction with two molecules of arylamidine [173]. Triazine formation is thought to proceed via condensation of the first amidine with 6 to give 7 and addition of the second amidine moiety to give 8, which unexpectedly cyclizes to 9 with elimination of NH3 and Meldrum s acid. 

The synthesis of diaryl-1,3i5-triazines 10, a new class of potent non-nucleoside reverse transcriptase inhibitors (NNRTIs) has been reported. The requisite amidines 8 were readily prepared from the corresponding phenylacelonitrilcs, while the isourea partners 9 were obtained in modest yields by the reaction of diphenyl cyanocarbonimidate with the appropriate aniline <01BMCL2229>. 

Various synthetic protocols were available for the preparation of 1,2,4-triazoles and derivatives thereof Efhcient synthesis of 3,4,5-tri-substituted 1,2,4-triazoles 171 was accompHshed from the reaction of guanidines 169 with 2,2,2-tri-chloroethylimidates 170 in PEG-400 (14TL177). 3,5-Diaryl-l,2,4-triazoles 173 were synthesized from a domino nucleophilic substitution/ oxidative cycfr-zation sequence from 2 equivalents of amidines 172 with copper catalyst, sodium bicarbonate as base, 1,10-phenanthroline as an additive, and K3[Fe(CN)6]/air as the oxidant (14T1635). Sulfur-substituted 1,2,4-triazoles... 

Meyer and Wagner reported that 4-quinazolones can also be formed by heating isatoic anhydride with amidines. They found that reaction of isatoic anhydride 38 with W,iV -diaryl formamides or W,A -diaryl acetamides 44 proceeded smoothly at moderate temperatures (120-140 °C) to give 45 along with the evolution of carbon dioxide. 

It was shown on some examples that the deprotection of the 2,5-diarylated amidines to give 2,5-disubstituted pyrrolidines was easily performed by treatment with H2NNH2/CF3CO2H (Scheme 18) [11]. 

Reviews have featured recent applications of organocatalysts to asymmetric aldol reactions, including particular focus on catalysis by small molecules. The effects of introduction of a diaryl (oxy)methyl group into chiral auxiliaries, catalysts, and dopants have been discussed and applications of amidine-, isothiourea-, and guanidine-based nucleophilic catalysts for a range of reactions of carbonyl compounds have been highlighted. " ... 

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