Palladium-catalyzed benzannulation from alkynes and allylic compounds

Area of Science:

• Organic Chemistry
• Catalysis
• Synthetic Methodology

Background:

• Efficient synthesis of polysubstituted benzenes is crucial in organic chemistry.
• Palladium-catalyzed reactions offer powerful tools for C-C bond formation.
• Allyl tosylates are versatile electrophiles in organic synthesis.

Purpose of the Study:

• To develop a regioselective synthesis of polysubstituted benzenes.
• To explore the use of palladium catalysts in alkyne annulation reactions.
• To investigate the preparation of complex aromatic and bicyclic compounds.

Main Methods:

• Reaction of various alkynes (terminal and internal) with allyl tosylates.
• Utilized palladium catalysts to promote cyclization and annulation.
• Employed allyl alcohols and p-toluenesulfonic anhydride as an alternative to pre-formed allyl tosylates.
• Investigated the cyclization of diynes with allyl tosylate.

Main Results:

• Achieved good to high regioselectivity in the formation of polysubstituted benzenes.
• Successfully synthesized pentasubstituted benzenes from internal alkynes.
• Readily prepared trisubstituted benzenes from terminal alkynes.
• Demonstrated the utility of in situ generated allyl tosylates.
• Synthesized bicyclic compounds containing an aromatic ring via diyne cyclization.

Conclusions:

• Developed a versatile and regioselective palladium-catalyzed method for synthesizing polysubstituted benzenes.
• The methodology allows for the construction of diverse aromatic scaffolds, including complex bicyclic systems.
• The use of allyl alcohols and p-toluenesulfonic anhydride offers a practical alternative for generating reactive intermediates.