Chemistry of acetylenic ethers. Part 88: Synthesis of β‐hydroxy‐alkynes, substituted at the α‐carbon atom

Abstract

AbstractMetallation of allenyl thioethers, R1CHCCHSC2H5 (I) (R1 = alkyl), by means of methyl‐ or butyl‐lithium in ether, followed by addition of aldehydes or ketones, R2R3C  O (R2 and R3 are H or alkyl), affords a mixture of the two carbinols R1CHCC[CR2R3C(OH)](SC2H5) (III) and R1CH[CR2R3(OH)] CCSC2H5 (IV). By treatment of the mixture with an excess of potassium amide in liquid ammonia IV is converted into the metallated β‐hydroxy‐alkyne R1CH[CR2R3(OH)]CCH (VI), probably via a nucleophilic substitution at sulfur. In the cases where R1  CH3, ethanethiol is eliminated from III with formation of the metallated enynyl alcohol HCCCHCH[CR2R3(OH)], (V). A number of alkylated derivatives RCCCHR1CH2OH have been prepared from VI (with R2 and R3 = H).