Practical Aspects of Syntheses Based on Enyne-Allenes

4 Practical Aspects of Syntheses Based on Enyne-Allenes 

Examples of the Formation of Indeno-Fused Structures via Fnyne-AIlenes 

Note A zwitterion structure is not essential here since the bridging CH radical can delocalize into the XY benzene ring with one resonance structure having the radical on the CH group ortho to X and ready for combination with the other radical. It would also be stabilized by any lone pairs on Y. 

Synthesis ofFluorene Derivatives in a Cascade Cyclization of Substituted Propargylic Alcohols 

The synthesis of polycyclic aromatic compounds from substituted propargylic alcohols is based on a cascade cyclization initiated by the action of thionyl chloride (in pyridine) proceeding, apparently, via a diradical generated from the intermediate chlorinated benzoenyne-allene [279, 280]. The synthesis of benzannulated enyne-allene has been successfully achieved using the Claisen rearrangement of propargylic alcohol acetates. This route was used for the direct synthesis of several 

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