Trivalent Organostibines: Sb,N Ligands in Double N-Arylation of Primary Amines toward Functionalized Carbazoles.

A Sb,N ligand ( L-Sb ) for Pd-catalyzed double N-arylation of primary amines was developed. This trivalent ligand L-Sb , containing a 5,6,7,12-tetrahydrodibenzo[ c , f ][1,5]azastibocine skeleton and stable under air and moisture, could be synthesized facilely on a gram scale from chlorostibine ( 1 ) and cyclopentylmagnesium bromide. L-Sb showed excellent catalytic performance in Pd 2 (dba) 3 -catalyzed double N-arylation of 2,2'-dibromo-1,1'-biphenyl ( 2 ) with primary amines ( 3 ), affording functionalized carbazoles in good yields. This Pd 2 (dba) 3 / L-Sb -catalyzed double N-arylation, the first example of the application of trivalent organostibines as a ligand in N-arylation, featured the following advantages: small catalyst loading, wide functional group tolerance, good yields, and ease of gram-scale synthesis.