Formamidinium salts

Disulfide dications are remarkably stable to water, in contrast to disulfonium dications. However, all they can be hydrolyzed by alkali water solution to give starting thiocarbonyl compound or more hydrolyzed product. For example, exposition of salt 157 to the aqueous NaOH gives formamidinium salt 158 and thiourea (Scheme 60).154... 

A series of vinylogous formamidinium salts and formamidines were reduced at the enamine and iminium double bonds by NaBH4 giving the corresponding 1,3-dia-minopropanes138,139 (Scheme 103). 

Deprotonation of formamidinium salts is by far the most popular way to generate diaminocarbenes [3]. A major advantage of this method is that deprotonation is a rapid reaction, even at low temperatures. However, hindered strong anionic bases are required, especially for open-... 

Phosphorus nitrile chloride forms adduct (10) with DMF in the ratio 1 4, which is useful for the preparation of formamidines and azavinylogous formamidinium salts. It is supposed that the dehydration of primary amides to nitriles with (PNChls as well as the formation of 2-alkylbenzothiazoles from 2-(methylthio)anilides and (PNChls in the presence of triethylamine proceed via similar adducts." ... 

The reaction of amine hydrochlorides with thioxoesters affords amidinium salts (155 equation 91). Formamidinium salts (156 equation 92) with bulky substituents at the nitrogens can be obtained by oxidation of AA A/ -trisubstituted or AA -disubstitut thioureas with peracetic acid. - Byproducts in this reaction can be ureas and thiourea trioxides. -Dimethylaminoacrolein reacts with dimethylamine hydrochloride to give (157 equation 93), the parent compound of the vinylogous amidinium salt series. - From AA -dimethylthiobenzamide and Al-sulfinyldimethylammonium tetrafluoroborate the benzamidin-ium salt (158 equation 94) was prepared. ... 

Ketene aminals can be transformed by various electrophilic reagents to amidinium salts, thus mineral acids, alkyl halides, A///-dialkyliminium salts, alkoxymethyleneiminium salts, formamidinium salts, acyl halides, diazonium salts, vinylogous amidinium salts,sulfonyl halides, ketene dichlorides ... 

An important synthesis for formamide acetals with bulky alkoxy groups or with -aryl substituents starts from the corresponding formamidinium salts or from bis(didkylamino)acetonitriles the reaction with alcoholic alkoxides furnishes the amide acetals (449 Scheme 83).7 -32.35 ju tjjg reaction of the azavinylogous formamidinium salt (450) with methanolic methoxide a mixture of -dimethylform-amide dimethyl acetal and its azavinylogous derivative is produced. 

V,1V,N JV -Tetrasubstituted formamidinium salts as well as bis(dialkylamino)acetonitriles have been reacted with alkali metal amides of secondary amines to give tris(dialkylamino)methanes (534 Scheme... 

Bis(TV-substituted)-cyclams have been prepared by a variety of reactions. Dioxo- or diiminecy-clams can be bis-substituted and then reduced. Starting from cyclam, 1,8-dimethyl-cyclam (108) can be prepared and further /ra ,v-bis-substi luted to form (109) (Scheme 28). The formamidinium salt (110) is 1,11-bis-substituted (111), and then hydrolyzed to form (112).107 The bicyclic oxamide (113) is 1,4-bis-substituted (114), and then hydrolyzed to form (115).108 Substitution for (30), R2 = Me, (CH2)2NH2, etc. produces /nmv-bis/V-substituted 2,6-pyridiyl macrocycles. 

Reaction of the tetrahydroquinoxalines 44 with triethyl orthoformate gave the bright-yellow formamidinium salts 45. Reduction of 45 (R = COaEt) with sodium borohydride in THF gave the colorless derivative 46 The latter compounds were also prepared from 44 by reaction with formaldehyde. The use of 5-formyluracil gave the substituted compound 47. ° These compounds were of interest as model systems for N, N °-methylenetetrahydrofolic acid (48). During these investigations the hydrolysis of the formamidinium salts 45 as a function of pH was... 

Chromanones.- Three new methods of preparing these compounds are noteworthy. Chromanone-2-acetaldehydes (94) were synthesized by the condensation of 2-hydroxyacetophenones with the vinologous formamidinium salt (93).103 The discovery that 4-chromanols (96) can be obtained by the reaction of salicylaldehyde with a dialkyla-ted enamine (95) at room temperature greatly increases the availability of the little known 3,3-dialkylchromanones (97) which are oxidation products of the chromanols. Bis(chromanone)piperazine (99) is similarly obtained from NN -bis(2-methylprop-1-enyl)piperazine (98).10 A photo-Fries rearrangement of aryl acrylates (100 R=H or Me) in a two-phase solvent system of benzene and aqueous alkali has given a convenient route to the chromanones (101) which have been reduced to the chromanol and then dehydrated.105... 

A dimeric form of SbC NCO (98), stable at low temperatures, has been isolated from a reaction between KSbCl5NCO and SbCls in solution in liquid SO2, but above room temperature the rearrangement to an s-triazene derivative (99) has been confirmed by an X-ray study. A new heterocycle (100) has been synthesized by the action of water on the formamidinium salt [C1C(0)N-MeCClNMeC(0)Cl] SbCle, which is the initial product when SbCls and methyl isocyanate are refluxed in carbon tetrachloride. ... 

S odium alcohol Syntheses with vinylogous formamidinium salts... 

Aminoethylidene)amino-methylene compds. 15 Enecarbodiimides Eneformamidines Enehydrazones a,P-Ethylenehydrazones Formamidinium salts, vinylogous N-Imidoylethylenimines... 

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