Reactions of 3-formlylindole N,N-dimethylhydrazones with dienophiles. A stereospecific addition

3-Formyl-1-methylindole N,N-dimethylhydrazone (1a) and 3-formylindole N,N-dimethylhydrazone (1b) react with methyl propiolate to give 3-cyano-1-methylindole (2a) and 3-cyanoindole (2b) respectively. When dimethyl acerylenedicarboxylate was used as a reagent the hydrazone (1a) afforded the nitrile (2a) and the pyridine (3) but in the reaction of the hydrazone (1b) an enantiomeric mixture of R,R and S,S dimethyl 1-(3-cyano-1-indolyl)-2-dimethylaminosuccinates (4) were obtained and their structures confirmed by X-ray single crystal analysis