Expedient synthesis of secondary amines bound to indole resin and cleavage of resin-bound urea, amide and sulfonamide under mild conditions

Highly efficient, new protocols for the attachment of primary amines to indole aldehyde resin using Ti(OiPr)4–NaBH4 and CH(OMe)3–NaBH3CN–HOAc are reported. Mild cleavage conditions for the release of urea, amide and sulfonamide products from the solid support using 1% trifluoroacetic acid (TFA) are developed.