A Novel Access to Tertiary and Secondary ortho-Aminophenylphosphines by Protected Group Synthesis and Palladium Catalyzed P-C Coupling Reactions
2014
Heßler, Antonella | Kottsieper, Konstantin W. | Schenk, Stefan | Tepper, Michael | Stelzer, Othmar
The dilithium salt 1a formed by ortho-metallation of N-tert-butoxycarbonylaniline (BOC-aniline) 1 with two equivalents of tert-butyllithium reacts with the chlorophosphines Ph₃₋ₙPClₙ (n = 1 -3) to yield the BOC protected ortho-aminophenylphosphines 2 - 4 in high yields. On deprotection of 2 - 4 with trimethylchlorosilane in the presence of phenol the HCl adducts of the ortho-aminophenylphosphines 5 -7 are formed which may be deprotonated with KOH or NaOH to give the neutral phosphines 5a -7a. The novel secondary phosphine 8 with two ortho-aminophenyl groups is accessible by cleavage of the P-C bond in 7a with metallic lithium and subsequent hydrolysis. The bifunctional 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 phenylphosphine the chiral secondary phosphine 9 is formed.
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