This is a good route for the construction of unsymmetrical ketones. Eg (1)BuLi (1)BuLi H*,HgCl2 (2)PhCH,Br (2)CHaBr H2O HaC CH2Ph H CH2Ph CH2Ph The dithiane can be thought of as a"masked"carbonyl group. Ketones from Carboxylic Acids Organolithium reagents are very reactive towards carbonyl compounds. So much so,that they even attack the lithium salts of carboxylate anions. These dianions can then be protonated,which generates hydrates,which then lose water and produce ketones E.g OH R-C-OH LiOH R-C-0-+Li R'-Li HO+ H20 -O-Li+ OH R-C-R carboxylic acid lithium carboxylate dianion hydrate ketone 92的rn6中enn Chl8 Ketones and Aldehydes (landscape) Page 10Ch18 Ketones and Aldehydes (landscape) Page 10 This is a good route for the construction of unsymmetrical ketones. E.g. The dithiane can be thought of as a "masked" carbonyl group. Ketones from Carboxylic Acids Organolithium reagents are very reactive towards carbonyl compounds. So much so, that they even attack the lithium salts of carboxylate anions. These dianions can then be protonated, which generates hydrates, which then lose water and produce ketones. E.g. H + , HgCl2 H2O H3C CH2Ph (1) BuLi O S S (2) PhCH2Br S S H CH2Ph (1) BuLi (2) CH3Br S S H3C CH2Ph