[2+2] Cycloaddition and electrophilic alkynylation reactions of 4-chloro-1,1,1-trifluorobut-3-yn-2-one and alkyl vinyl ethers

Abstract

Reaction of 4 chloro 1,1,1 trifluorobut 3 yn 2 one with alkyl vinyl ethers leads to the parallel formation of [2+2] cycloaddition and electrophilic alkynylation products, the ratio of which depends on the nature of vinyl ether. Preparative methods for the separation of com pounds formed are suggested.

Synthesis of (+)-7,20-Diisocyanoadociane and Liver-Stage Antiplasmodial Activity of the Isocyanoterpene Class

“…This short sequence could generate large quantities of 3 , but its instability prevented its isolation and storage, so it was used crude and immediately. Highly substituted dendralene 4 proved to be more difficult to access, so we turned to the tandem [2 + 2] cycloaddition/retroelectrocyclization reaction reported for electron-deficient alkynes in the hope that this process could be applied to simple alkynones. In the absence of Lewis acid, 4-bromo-2-butynone ( 8 ) and ethyl vinyl ether do not react, but trimethylaluminum catalyzes their cycloaddition to form 9 , and over time retroelectrocyclization occurs to deliver 10 in 56% yield as a single geometrical isomer.…”