Useful procedures for fluorocyclization of tryptamine and tryptophol derivatives to 3a-fluoropyrrolo[2,3-b]indoles and 3a-fluorofuro[2,3-b]indoles

Versatile procedures for fluorocyclization of various tryptamine and tryptophol derivatives to obtain the corresponding 3a-fluoropyrrolo[2.3-b]indoles and 3a-fluorofuro[2.3-b]indoles, respectively were developed employing N-fluoro-2,4,6-trimethylpyridinium triflate (FP-T300) or Selectfluor™ as the electrophilic fluorinating agent. The use of NaHCO3 for fluorocyclization was effective in improving the yield of acid-labile fluoropyrrolo(furo)indoles. Our procedures are especially useful for the synthesis of fluoropyrrolo(furo)indoles bearing a free NH indole group.