Hydrogenation cinnamonitrile

Analogous ring closures are to be found in the cyclizations of cinnamonitriles (191 R1 = C1, R2 = H and R OH, R2 = Ar) to 2-benzazepin-l-ones (192) and (193 R = aryl) with hydrogen chloride and polyphosphoric acid respectively (74AHC(17)45>. Polyphosphoric acid has also been used to effect cyclization of the mono- or di-nitriles (191 R1 = OH,... 

Hydrogen bromide (but not the chloride) has a catalytic effect on the cyclization of alkenylbenzenes with sulphur. Undo mildly basic conditions, cinnamonitriles on heating with disulphur dichloride give the synthetically useful chloronitriles... 

Aldehydes are also obtained in variable yields from the lithium-methylamine reduction of carboxamides/ Cinnamaldehyde or 3-phenylpropanal can be prepared by the Raney nickel-catalysed hydrogenation of cinnamonitrile, though the generality of the method is not reported/ ... 

Amides can also be very effective inhibitors. For example, dicyandlamide provides steel with >90% protection in 4% (1N) HCI (also in H2SO4) up to at least 129°F (54°C). Nitriles, such as cinnamonitrile, are good inhibitors for both iron dissolution and hydrogen absorption, but they are not widely used. In contrast, imidazolines are popular. Kataoka and Takada filed patents on various imidazoline derivatives, and Patel et al. found that benzimidazoles are effective for copper and brass in HCI. A combination of amino and azo groups seems to work very well. For example, D Errico discovered that dialkylaminomethyi aromatic triazoles are effective in 5% HCI at 171°F (77°C). 

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