We report the application of the Pd(II)-catalyzed, directing group-aided C-H arylation/alkylation tactics to functionalize pyrene core, especially, the relatively inaccessible C2 and K-region C10 positions of pyrene core and augmentation of the library of pyrene derivatives with C1,C2- and C1,C10-disubstituted pyrene motifs. The Pd(II)-catalyzed β-C-H arylation/alkylation of the C2-position of pyrene-1-carboxamide possessing 8-aminoquinoline directing group yielded various C1,C2-disubstituted pyrenes. Similarly, the Pd(II)-catalyzed selective γ-C-H arylation/alkylation of the C10-position of N-(pyren-1-yl)picolinamide possessing picolinamide directing group yielded various C1,C10-disubstituted pyrenes. Examples of C(9)-H arylation of pyrene-1-carboxamide and the removal of the directing group after the C-H arylation/alkylation reactions were also shown. The structures of representative pyrene derivatives were confirmed by the X-ray structure analysis. Given the importance of the pyrene derivatives in various fields of chemical sciences, this report is a contribution towards augmentation of the library of pyrene derivatives with C1,C2- and C1,C10-disubstituted pyrene amide motifs.
We have shown our efforts toward expanding the utility of the relatively inexpensive pyridine-N-oxide directing group in the Pd(II)-catalyzed site-selective γ-C(sp 2 )À H, γ-C(sp 3 )À H and δ-C(sp 2 )À H functionalization. The functionalization βÀ CÀ H bonds using bidentate directing group (DG) pyridine-N-oxide which operates through the N,O-coordination mode has been well documented in the literature. However, there exist rare reports dealing with the functionalization of remote sp 2 /sp 3 γand δ-CÀ H bonds of carboxamides assisted by the bidentate directing groups operating via the N,O-coordination. In this paper, the scope of pyridine-N-oxide DG was examined for accomplishing the siteselective (mono) γ-C(sp 2 )À H arylation in substrates containing competitive C(sp 3 )À H and C(sp 2 )À H bonds. The investigation has enabled to assemble a library of pyridine-N-oxide-based biarylacetamides, heteroaryl-based biaryl carboxamides, tricyclic quinolones, arylheteroarylmethanes, biaryl-based aliphatic carboxamides and mono (ortho) arylated phenylglycine derivatives. In general, biaryl derivatives and in particular, arylacetamide, arylacetic acid derivatives and pyridine-N-oxide (2-aminopyridyl) motifs are medicinally relevant classes of compounds. This work enabled the assembling of a library of the above-mentioned types of compounds through the pyridine-N-oxide directing groupaided site-selective sp 2 /sp 3 γ-CÀ H and sp 2 δ-CÀ H functionalization of carboxamides.
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