Tandem Horner–Wadsworth–Emmons/Heck procedures for the preparation of 3-alkenyl-oxindoles: the synthesis of Semaxanib and GW441756

A tandem sequence involving Horner–Wadsworth–Emmons (HWE) olefination followed by a palladium-catalysed intramolecular Heck reaction has been developed to provide rapid access to 3-alkenyl-oxindoles from α-halo-anilides. This one-pot microwave accelerated process proceeds with catalytic palladium(II) acetate or tetrakis(triphenylphosphine)palladium, and has been used to prepare a range of adducts derived from aromatic, heteroaromatic and aliphatic aldehydes. The procedures can be used to prepare N-unprotected oxindoles directly and the applicability of the process has been established by carrying out one-pot syntheses of Semaxanib, an angiogenesis signalling inhibitor, and GW441756, an aza-oxindole Trk A inhibitor.