Published on 01 January 1986. Downloaded by google on 13/02/2016 20:40:24. ... View Article Online / Journal Homepage / Table of Contents for this issue ... (14) a; R' = C02Me, R2= H b; R'= H, R 2 = C0,Me ... A survey of carbonyl compounds containing the moiety O=CC=X (Scheme 1) has shown that ninhydrin, isatin, acenaphthaquinone, phenylglyoxaldehyde, ethyl glyoxylate, and pyridine-2-carbaldehyde all function as suitable precur- sors of dipoles. ...