Biaryl phosphane ligands in palladium-catalyzed amination

Orthogonal Cu- and Pd-based catalyst systems for the O- and N-arylation of aminophenols

O- or N-arylated aminophenol products constitute a common structural motif in various potentially useful therapeutic agents and/or drug candidates. We have developed a complementary set of Cu- and Pd-based catalyst systems for the selective O- and N-arylation of unprotected aminophenols using aryl halides. Selective O-arylation of 3- and 4-aminophenols is achieved with copper-catalyzed methods employing picolinic acid or CyDMEDA, trans-N,N'-dimethyl-1,2-cyclohexanediamine, respectively, as the ligand. The selective formation of N-arylated products of 3- and 4-aminophenols can be obtained with BrettPhos precatalyst, a biarylmonophosphine-based palladium catalyst. 2-Aminophenol can be selectively N-arylated with CuI, although no system for the selective O-arylation could be found. Coupling partners with diverse electronic properties and a variety of functional groups can be selectively transformed under these conditions.

Pd-catalyzed conversion of aryl chlorides, triflates, and nonaflates to nitroaromatics

An efficient Pd catalyst for the transformation of aryl chlorides, triflates, and nonaflates to nitroaromatics has been developed. This reaction proceeds under weakly basic conditions and displays a broad scope and excellent functional group compatibility. Moreover, this method allows for the synthesis of aromatic nitro compounds that cannot be accessed efficiently via other nitration protocols. Mechanistic insight into the transmetalation step of the catalytic process is also reported.

Tris(4-tert-butyl-phen-yl)phosphine oxide

In the title compound, C(30)H(39)OP, the P=O bond length is 1.4866 (12) Å and the P-C bond lengths range from 1.804 (2) to 1.808 (13) Å. The molecle is located on a crystallographic mirror plane. The methyl groups of one tert-butyl group are disordered over two sites in a 0.776 (4):0.224 (4) ratio.

CuI-catalyzed amination of arylhalides with guanidines or amidines: a facile synthesis of 1-H-2-substituted benzimidazoles

CuI/L5 (N,N'-dimethylethylenediamine) proves to be an efficient catalyst system for the amination of arylhalides with guanidines. The same catalyst system is then successfully applied to the one-step synthesis of 1-H-2-amino-benzimidazoles through tandem aminations of 1,2-dihaloarenes in modest yields. This methodology is also applicable for the preparation of 1-H or 1-substutituted 2-aryl- or 2-alkyl-benzimidazoles.

Pd-catalyzed N-arylation of secondary acyclic amides: catalyst development, scope, and computational study

We report the efficient N-arylation of acyclic secondary amides and related nucleophiles with aryl nonaflates, triflates, and chlorides. This method allows for easy variation of the aromatic component in tertiary aryl amides. A new biaryl phosphine with P-bound 3,5-(bis)trifluoromethylphenyl groups was found to be uniquely effective for this amidation. The critical aspects of the ligand were explored through synthetic, mechanistic, and computational studies. Systematic variation of the ligand revealed the importance of (1) a methoxy group on the aromatic carbon of the "top ring" ortho to the phosphorus and (2) two highly electron-withdrawing P-bound 3,5-(bis)trifluoromethylphenyl groups. Computational studies suggest the electron-deficient nature of the ligand is important in facilitating amide binding to the LPd(II)(Ph)(X) intermediate.