Enamines as Precursors to Polyfunctional Heteroaromatic Compounds; a Decade of Development

Recent synthesis and utilization of enamines as precursors for heterocyclic and carbocyclic compounds are reviewed.Two general synthetic routes for preparation of enamines based on condensation and addition reactions.Enamines and azaenamines can be used as building blocks for carbocyclic, fiveand six-membered heterocyclic as well as fused heterocyclic compounds.Me R O Scheme 4 DMF-DMA R O NMe 2 R O NMe 2 12 13A xylene 13BThe reaction of methyl function in 2-butenenitriles 14 and heterocyclic carbonitriles 15-17 with DMF-DMA proceeds much faster and is generally conducted in refluxing toluene for 6 h and yields, in each case, trans enamines 18-21 in good yields. 68Preparation of enamines 18-21 under microwave irradiation in the presence of acetic acid was also investigated.Reactions under these conditions proved much faster (5-10 minutes) and gave better yields than conventional heating 54 (Scheme 5).