Solvent-Free Heck-Jeffery Reactions under Ball-Milling Conditions Applied to the Synthesis of Unnatural Amino Acids Precursors and Indoles

The syntheses of various amino- and hydroxy-substituted dehydrophenylalanine derivatives using the Heck-Jeffery protocol under non-solvent conditions in a ball mill are presented. The influences of electron-withdrawing groups and of the location of the heteroatom substituent relative to the halide are discussed. Suitably substituted ortho-amino dehydrophenylalanine derivatives undergo a cyclization-elimination reaction to the corresponding 2-substituted indoles.