Flow synthesis of (3R)- and (3S)-(E)-1-iodohexa-1,5-dien-3-ol: Chiral building blocks for natural product synthesis

A concise procedure to prepare optically active (3R)- and (3S)-(E)-1-iodohexa-1,5-dien-3-ol was developed. Ethyl (E)-3-iodoacrylate was converted to racemic (E)-1-iodohexa-1,5-dien-3-ol under flow and batch conditions via successive half reduction followed by Grignard reaction. Kinetic resolution of the racemic alcohol was achieved under flow conditions by using lipase packed in a column to afford (3S)-(E)-1-iodohexa-1,5-dien-3-ol and corresponding (3R)-acetate. Removal of the acetyl group was also carried out under flow conditions by using ion exchange resin packed in a column and (3R)-(E)-1-iodohexa-1,5-dien-3-ol was obtained after simple evaporation of the eluent.