Rapid and Multigram Synthesis of Vinylogous Esters under Continuous Flow: An Access to Transetherification and Reverse Reaction of Vinylogous Esters

• Nirmala Mohanta
• Moreshwar B. Chaudhari
• Naveen Kumar Digrawal
• Boopathy Gnanaprakasam*

• Department of Chemistry, Indian Institute of Science Education and Research, Pune 411008, India

An environmentally benign approach for the synthesis of vinylogous esters from 1,3-diketone and its reverse reaction under continuous-flow has been developed with alcohols in the presence of inexpensive Amberlyst-15 as a catalyst. This methodology is highly selective and general for a range of cyclic 1,3-dicarbonyl compounds which gives a library of linear alkylated and arylated vinylogous esters in good to excellent yield under solvent and metal free condition. Furthermore, the long-time experiment in a continuous-flow up to 40 h afforded 8.0 g of the vinylogous ester with turnover number (TON) = 28.6 and turnover frequency (TOF) = 0.715 h–1 using Amberlyst-15 as a catalyst. Furthermore, a continuous-flow sequential transetherification of vinylogous esters with various alcohols has been achieved in high yield. Reversibly, this vinylogous ester was deprotected or hydrolyzed into ketone using environmentally benign water as a solvent and Amberlyst-15 as a catalyst under continuous-flow process.

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