Aldehydes, from imidoyl chlorides

The synthesis of aldehydes from imidoyl chlorides via reduction and hydrolysis of the azomethine has been demonstrated by Sonn and Muller who used stannous chloride as the reducing agent. 

By a similar process, von Braun and Rudolph459 obtained unsaturated aldehydes from the imidoyl chlorides derived from anilides of <%,/ -unsaturated acids the reaction proceeds by way of the Schilf bases, which are then hydrolysed to the aldehydes. 

Lewis acid catalysis serves for the Passerini-type reaction of aldehydes with isocyanides forming a-hydroxyamides. The catalytic system consisting of SiCU and (107) provides high yield and good to excellent enantioselectivity for the addition of t-butyl isocyanide to a wide range of aldehydes [167]. The amide product is formed from the imidoyl chloride intermediate (110) by hydrolysis (Scheme 9.78). Treatment of the intermediate product with methanol followed by hydrolysis gives a-hydroxyesters with the retention of enantioselectivity. 

The synthesis of analogous iminoacyl complexes by isonitrile insertion into linear alkyl-zirconocene chlorides is also known. In an overall regiospecific hydrocyanation of alkenes, iminoacyls 21 derived from tBuNC or Me3SiCN (as the Me3SiNC isomer) may be treated with I2 to rapidly generate an imidoyl iodide and subsequently the nitrile 22 (Scheme 3.6) [22], Less hindered iminoacyl complexes (e. g. R = Bu, Cy) may be hydrolyzed to afford aldehydes 23 [23]. 

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