Facile Hetero‐ Diels‐Alder Reaction of α,β‐Unsaturated Acyl Cyanides and Enol Ethers: Syntheses of 2‐Alkoxy‐3,4‐dihydro‐2 H ‐Pyran‐6‐carbonitriles

2‐Ethoxy‐3,4‐dihydro‐2 H ‐pyran‐6‐carbonitriles are obtained in high yield by stereospecific endo ‐mode cyclo‐additions of α,β‐unsaturated acyl cyanides and ethyl vinyl ether at room temperature. The nitrile group is converted to some other functionalities.