Metal atom reactions with nitriles

A characteristic feature of contemporary investigations in the held under consideration, is the interest in cycloaddition reactions of nitrile oxides with acetylenes in which properties of the C=C bond are modified by complex formation or by an adjacent metal or metalloid atom. The use of such compounds offers promising synthetic results. In particular, unlike the frequently unselec-tive reactions of 1,3-enynes with 1,3-dipoles, nitrile oxides add chemo-, regio-and stereoselectively to the free double bond of (l,3-enyne)Co2(CO)6 complexes to provide 5-alkynyl-2-oxazoline derivatives in moderate to excellent yield. For example, enyne 215 reacts with in situ generated PhCNO to give 80% yield of isoxazoline 216 (372). 

The use of organomagnesium reagents as bases leads to complexation of the nitrile imines (e.g., 141), which has been found to have a strong effect in promoting syn selectivity in reactions with methyl 2-(l-hydroxyalkyl)acrylates via coordination of the metal atom with the alcoholic oxygen (e.g., leading to the formation of 142). Lithium complexation had little effect (78). 

Now let me come back to primary substitutions at the ferrocene nucleus. Together with Vil chevskaya, we phosphorylated ferrocene and its derivatives to triferrocenylphosphine oxides [263, 264). An unusual reaction, discovered in collaboration with Perevalova and Yur eva, was the direct cyanation of ferrocene with hydrocyanic acid in the presence of ferric chloride [265,272). Initially, cyanide attacks the iron atom of the ferricinium cation, then the cyanide group transfers to the ring while the iron is simultaneously reduced. The reaction was termed by us as the ricochet (from the metal to the nucleus) substitution it may be applied to many substituted ferrocenes and to the ruthenocenium cation [273), and it is now the simplest route to ferrocene carboxylic acids through their nitriles. Further, ferrocene was studied in acid-medium reactions with oxo compounds. With aldehydes [274), the reaction was complicated by the transformation of ferro-cenylalkyl carbinol formed Initially via the carbonium ion, followed by transformation to a radical which, in its turn, was coupled to 1,2-bis-(ferrocenylalkyl)ethane (27.5). The reaction with acetone led to 2,2-di-ferrocenylpropane (276). 

Reactions of the nitrile group(s) In general, these reactions start with a nucleophilic attack at the C atom of the nitrile group. Thus 10 reacted with its anion in basic media to yield the dimerization product 2-amino-1,1,3-tricyanopropene . Thiolysis with H2S gave cyanothioacetamide. Acidic alcoholysis in an neutral solvent produced dialkyl propanediimidate dihydrohalides Metal-catalyzed reactions of 10 with methyl acetoacetate and other j5-dicarbonyls have been reported. ... 

Following the well-known Pinner synthesis of imidates by the reaction of nitriles with alcohols, there has been considerable interest in recent years in treating a nitrile bond within the coordination sphere of metal ions with water or alcohols. It has been suggested that the initial step consists of nucleophilic attack of an external or coordinated hydroxide or alkoxide anion on the nitrile carbon atom. A number of imidate complexes have been isolated from the reactions of 2-cyanopyridine with metal [Cu", Ni , Co" and Fe"] salts in alcohols, of frans-PtMeClL with pentafluorobenzonitrile and silver hexafluorophosphate in alcohols," and of o-cyanobenzylplati-num complexes. "... 

Coordination of nitrile to metal directly through the nitrogen or through some other proximal atom activates the carbon toward nucleophilic attack by water and other nucleophiles. The products are commonly amides. The metal-mediated reactions of dicyanodiamide (19) have been further investigated in the presence of nickel or copper salts (19) reacts with alcohols to yield (20). 

The reactions of bare M" " ions with organic substrates in the gas phase continue to attract attention. Comparative studies across the first row transition metals have been made with nitriles 233 and halobenzenes, and trends in the M+-CH3 dissociation energy have been interpreted.35 Collisional activation of the Fe propane complex by Xe atoms has been examined, ... 

The two reactive chlorine atoms at the opposite ends of the phosgene molecule determine the use of phosgene for addition reactions, polymerization reactions and for chain-enlargements. Other uses of phosgene are reactions with secondary amines to give imidoyl chlorides, with tertiary amines to form cationic complexes, with nitriles to produce heterocycles and with metal oxides to produce metal chlorides. 

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