Ene Reaction - Ene Component

Ene Component

Enes are π-bonded molecules that contain at least one active hydrogen atom at the allylic, propargylic, or α-position. Possible ene components include olefinic, acetylenic, allenic, aromatic, cyclopropyl, and carbon-hetero bonds. Usually, the allylic hydrogen of allenic components participates in ene reactions, but in the case of allenyl silanes, the allenic hydrogen atom α to the silicon substituent is the one transferred, affording a silylalkyne. Phenol can act as an ene component, for example in the reaction with dihydropyran, but high temperatures are required (150–170°C). Nonetheless, strained enes and fused small ring systems undergo ene reactions at much lower temperatures. In addition, ene components containing C=O, C=N and C=S bonds have been reported, but such cases are rare.