1. Synthesis of Alkynyl Ethers and Sigmatropic Rearrangement of Allyl and Benzyl Alkynyl Ethers Thomas Minehan Department of Chemistry and Biochemistry, California State University, Northridge
Combination of -diazoketones 1 and alcohols 2 in the presence of an indium triflate catalyst gives rise to -alkoxy ketones 3, which may be transformed directly into either enol triflates or phosphates 4 in high chemical yields. Subsequent treatment with the non-nucleophilic base t-BuOK at -78°C then gives rise to alkynyl ethers 5 of varying substitution patterns R1, R2.
When allylic alcohols are used in this procedure, the intermediate allyl alkynyl ethers undergo rapid [3,3]-sigmatropic rerrangement at temperatures as low as -85°C to furnish an allyl ketene intermediate; subsequent addition of 1°, 2°, 3° alcohols or amines lead to unsaturated esters or amides 6 in high yields. Similarly prepared benzyl alkynyl ethers are stable at room temperature but rapidly rearrange at 60°C in toluene to furnish 2-substituted indanones 7.