One-Pot Synthesis of Indoles by a Sequential Ugi-3CR/Wittig Reaction Starting from Odorless Isocyanide-Substituted Phosphonium Salts

A new one-pot preparation of indoles by a Ugi-3CR/Wittig sequence has been developed. The reaction of odorless isocyanide-substituted phosphonium salt 5, aldehyde 6, and amine 7 produced the indoles 9 in 45-82% yields via a sequential Ugi-3CR/Wittig reaction in the presence of H3PO4 and solid K2CO3, respectively.