Organic Letters
Letter
pyridine under similar conditions,13 3-pyridinesulfonamide
(1h) afforded the corresponding C6-alkylated pyridine (3he;
entry 7). In addition, morpholino(phenyl)methanone (1i)
furnished the corresponding alkylated product in good
selectivity (entry 8). This catalytic system also exhibited similar
reactivity for the alkylation of aromatic sulfones. For example,
methyl phenyl sulfone (1j) afforded the respective para-
alkylated sulfone in good yield (entry 9). For diphenyl sulfone
(1k), a dialkylation was observed to generate 4,4′-dialkyl-
diphenylsulfone (3ke; entry 10). Unfortunately, methyl phenyl
sulfoxide did not afford any alkylation products.
regiocontrol of the C−H activation step as in the case of
benzamides.
In summary, we have developed a method for the para-
selective alkylation of benzenesulfonamides and aromatic
sulfones based on cooperative nickel/aluminum catalysis.
Combined with conventional methods, the controlled
functionalization of selected C−H bonds in benzene-
sulfonamides is now possible.
ASSOCIATED CONTENT
* Supporting Information
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S
The aminosulfonyl group of 3be could be removed by a
known nickel-catalyzed method8 to afford the corresponding
1,3-disubstituted benzene 4 in good yield (Scheme 2). As 1b
The Supporting Information is available free of charge on the
Experimental procedures and characterization data of
Scheme 2. Synthesis of 1,3-Disubstituted Benzenes
AUTHOR INFORMATION
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Corresponding Author
ORCID
Notes
could be obtained via ortho-lithiation8 followed by methylation
with iodomethane, the overall process represents an example of
the synthesis of 1,3-disubsituted benzenes through the
combination of the newly developed para-alkylation reaction
demonstrated herein with known transformations of arene-
sulfonamides.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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This work was supported by the CREST program “Establish-
ment of Molecular Technology towards the Creation of New
Functions” Area from JST and by Grant-in-Aids for Young
Scientists (A) (No. 25708006) and for Research on Innovative
Areas “Precise Formation of a Catalyst Having a Specified Field
for Use in Extremely Difficult Substrate Conversion Reactions”
(No. 15H05799) from MEXT.
A plausible reaction mechanism for the transformation is
outlined in Scheme 3 based on that for the para-alkylation of
Scheme 3. A Plausible Mechanism for the para-Selective
Alkylation of Sulfonylarenes
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benzamides supported by DFT studies.12 Bis(alkene)nickel(0)
complex 5 undergoes ligand exchange with a sulfonylarene/
MAD adduct to form σ-complex 8 through alkene-ligated
nickel(0) 6 and π-complex 7. The C−H bond is cleaved, and
alkyl(aryl)nickel(II) complex 9 is formed through concerted
ligand-to-ligand hydrogen transfer.14,15 A geometrical isomer-
ization generates T-shaped nickel(II) complex 11 via its isomer
10 before reductive elimination forging the C−C bond. The
aluminum catalyst would play key roles in both acceleration and
C
Org. Lett. XXXX, XXX, XXX−XXX