Borane-Induced Dimerization of Arylallenes.

Area of Science:

• Organometallic Chemistry
• Organic Synthesis
• Catalysis

Background:

• Allenes are versatile organic compounds with unique reactivity.
• Boranes are important reagents in organic synthesis, particularly for borylation reactions.
• Cope rearrangements are powerful tools for carbon-carbon bond formation.

Purpose of the Study:

• To investigate the reaction of arylallenes with bis(pentafluorophenyl)borane.
• To explore the formation of borylated diene coupling products.
• To elucidate the reaction mechanism, including potential rearrangements.

Main Methods:

• Reaction of various arylallenes with bis(pentafluorophenyl)borane (HB(C6F5)2) in a 2:1 molar ratio.
• Characterization of reaction products using spectroscopic techniques.
• Analysis of reaction intermediates and mechanistic pathways, including thermal rearrangements.

Main Results:

• A series of arylallenes successfully coupled with HB(C6F5)2 to yield tail-to-tail 1,6-diaryl-2-boryl-hexa-1,5-diene products.
• The reaction with phenylallene initially formed a head-to-head coupled product.
• This intermediate underwent a thermally induced Cope rearrangement to afford the final tail-to-tail product.

Conclusions:

• The reaction provides a novel route to synthetically useful borylated dienes.
• The study highlights the importance of Cope rearrangements in controlling product selectivity in allene coupling reactions.
• This methodology offers a new strategy for constructing complex organic molecules.