Selective Synthesis of Polycyclic 2‐Oxaspiro[5.5]undecanones and Diaryl Allylic Alcohols From Propargyl Benzyl Ethers Using an NXS–Water System

ABSTRACT

Herein, we report an approach for the selective construction of 2‐oxaspiro[5.5]undecan‐9‐ones as well as 3,3‐diaryl allylic alcohols by employing propargyl‐benzyl ethers in N‐halosuccinimide‐water (NXS‐H ₂ O) system. This methodology shows a broad substrate scope for propargyl‐benzyl ethers, resulting in a selective construction of a structurally divergent library of 2‐oxaspiro[5.5]undecan‐9‐ones, when employed (2:1) CH ₃ CN: H ₂ O and NXS reagents. Further, it was extended for the construction of bis‐spiro systems as well. By tuning the conditions to (50:1) CH ₃ CN: H ₂ O, we could also selectively promote the migration of e‐rich arenes to obtain the corresponding 3,3‐diarylallylic alcohols. In the case of trimethoxy‐arene (migrating group), a selective formation of benzo[c]oxepanes was observed via an intramolecular iodo‐cyclization through 7‐endo‐dig fashion.