Synthesis of Isomeric Acetylfurancarbaldehydes and Their 5-Adamantanyl Analogs

A convenient method was proposed for the synthesis of 2-acetylfuran-3-carbaldehyde and 3-acetylfuran-2-carbaldehyde based on the known 2-acetyl-3-bromomethyl- and 2-bromomethyl-3-acetylfuran. Acid chlorides of 5-adamantanyl-3-methylfuran-2-carboxylic and 5-adamantanyl-2-methylfuran-3-carboxylic acids were converted via furoylmalonates and their acid hydrolysis into 5-(adamantan-1-yl)-3-methyl-2-acetylfuran and 5-(adamantan-1-yl)-2-methyl-3-acetylfuran. Bromination of these compounds with N-bromosuccinimide yielded bromomethyl derivatives, which were converted into the corresponding acetates using sodium acetate. Alkaline hydrolysis of the latter gave 5-(adamantan-1-yl)(hydroxymethyl)acetylfurans. These ketols were oxidized at 0–5°C with an acidified aqueous solution of sodium dichromate in a diethyl ether–water biphasic system to the corresponding 5-(adamantan-1-yl)(formyl)acetylfurans.