Formamidinium syntheses with

A recently published new synthesis of dinitrosomethanides salts (DNM = rfinitroso-methanide) starts from formamidinium nitrate (8), which represents an easily accessible source for an NC(H)N unit . Treating a methanolic solution of 8 and hydroxylammonium nitrate (two equivalents) with a methanolic solution of KOBu-t (two equivalents) results in the formation of the labile intermediate Af,Af -dihydroxyformamidinium nitrate (9) (Scheme 8). The reaction of 9 with MOBu-t (two equivalents, M = alkali metal) in the presence of oxygen yields the deep blue alkali DNM salt (7), which can easily be purified by recrystaUization from methanol (yield 60-70%) . 

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. 

Many vinylogous amidinium salts, e.g. (185) and (186) (Scheme 25), are readily available by double formylation of CH2-acidic or alkenic compounds. Reviews on the chemistry of vinylogous amidinium salts are available. The first azavinylogous formamidinium salt (187 Scheme 26) was prepared in 1960 by reaction of DMF with cyanuric chloride. The mechanism of this reaction has been established.Based on these findings new methods for the synthesis of these compounds were developed, e.g. the reaction of isocyanatomethyleneiminium salts with tertiary formamides affords salts (187). - In the synthesis of the salts (187) cyanuric chloride can be replaced by phosphorus nitride chloride (PNCl2)3.3 <... 

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