Direct Arylation

Speaker: Chien-An ChenTeacher: Guey-Sheng Liou

Important bi(hetero)aryls

Direct Arylation V.S. Traditional Cross-Coupling

Advantage of direct arylation:

1. Without metallic halides by-product

→good for enviorment

2. Reduce the synthetic operations →economical

Define of direct arylation:Through cleavage of C-H bond

Category of Direct Arylation

Direct Arylation with Organometallic Reagents (Rh-cat.)

Direct Arylation with Organometallic Reagents (Pd-cat.)

Direct Arylation with Organometallic Reagents (Ru-cat.)

Dehydrogenative Arylation

Direct Arylation with (Pseudo)Halides (Pd-cat.)

Direct Arylation on LBG polymer

Ullrich Scherf et al. , ACS Macro Lett. 2012, 1, 465−468

Direct Arylation on LBG polymer

Takaki Kanbara et al. , ACS Macro Lett. 2012, 1, 67−70

Direct Arylation on LBG polymer• Disadvantage:The critical factor of direct arylation polymerization is regioselectivity. Example:

Solution method: Use protecting group, methyl, to protect 3-position of thiophene. Example:

The two hydrogen atoms are also reactive

Cross-linked polymer

Conclusion

• Until very recently, the majority of catalytic direct arylations have been accomplished with palladium, rhodium, or ruthenium catalysts. However, less-expensive copper, iron, and nickel compounds have been shown.

• The use of atom-economical terminal oxidants and achieving regioselectivity in intermolecular arylations remain significant challenges.