A novel access to tertiary and secondary ortho-aminophenylphosphines by protected group synthesis and palladium catalyzed P-C coupling reactions

The dilithium salt la formed by ortho-metallation of N-tert-butoxycarbonyla niline (BOC-aniline) 1 with two equivalents of tert-butyllithium reacts wit h the chlorophosphines Ph3-nPCln (n = 1 - 3) to yield the BOC protected ort ho-aminophenylphosphines 2 - 4 in high yields. On deprotection of 2 - 4 wit h trimethylchlorosilane in the presence of phenol the HCl adducts of the or tho-aminophenylphosphines 5 - 7 are formed which may be deprotonated with K OH or NaOH to give the neutral phosphines 5a - 7a. The novel secondary phos phine 8 with two ortho-aminophenyl groups is accessible by cleavage of the P-C bond in 7a with metallic lithium and subsequent hydrolysis. The bifunct ional P,N ligands 6 or 6a are alternatively accessible by Pd-catalyzed P-C coupling of ortho-iodoaniline with phenylphosphine. If a 1:1 stoichiometry is employed in the coupling reaction of ortho-iodoaniline and phenylphosphi ne the chiral secondary phosphine 9 is formed.