Tin for Organic Synthesis, 14 . Synthesis of Aromatic and α,β‐Unsaturated Aldehydes by a Friedel‐Crafts‐like Electrophilic Destannylation Using 1,1‐Dichloromethyl Methyl Ether

A mild and effective method for the preparation of a variety of aromatic ( 7a–m ), heteroaromatic ( 7n–r ), and α,β‐unsaturated aldehydes ( 8a–f ) is described. The reaction of trialkylaryl‐ ( 2a–o ), heteroaryl‐ ( 2p–t ), and 1‐alkenylstannanes ( 4a–f and 5a–f ) with dichloromethyl methyl ether ( 1 , DCME) in the presence of aluminium trichloride followed by hydrolysis provides the corresponding aldehydes. In the case of arylstannanes the ipso ‐isomers are generally formed; the p ‐alde‐hydes occur as side products. The electrophilic substitution of 1‐alkenylstannanes with 1 leads to α,β‐unsaturated aldehydes in an ipso ‐ and stereospecific manner. A comparison of the leaving abilities of the stannyl and silyl groups shows a lower or even zero reactivity of the silyl‐substituted compounds 6a–c towards the electrophile 1 . In the silylstannylal‐kene 6c only the stannyl group reacts whereas the stannyl function remains unaffected in the product, aldehyde 11 .