Novel functionalized titanium(IV) benzylidenes for the traceless solid-phase synthesis of indoles

[GRAPHICS] Titanium(IV) benzylidenes bearing a masked nitrogen nucleophile in the ortho position converted Merrifield resin-bound esters into enol ethers. An unusual nitrogen protecting group, N-silylated tert-butyl carbamate, was employed. One percent TFA released N-Boc indoles in high yield and purity. N-Methyl indoles were also prepared. Cyclative termination was not required to release the chameleon catch. The first example of a carbonyl group within a titanium alkylidene reagent is reported.