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Photoinduced Alkynylation of Alkylboronic Acids and Alkyl-Boronates via Aminyl Radical Transfer (ART) Strategy
Akash Bisoyi1, Ruveen Murgeshan1, Gayathri K G1
1School of Chemistry, Indian Institute of Science Education and Research, Thiruvananthapuram, India.
Abstract:
We have developed a practical and innovative method for the photoinduced alkynylation of alkylboronic acids/alkyl-boronates, using (hetero)aryl acetylenic bromides as alkynylating reagents and morpholine as an activator. This catalyst-free reaction features a broad substrate scope, efficiently accommodating various alkylboronic acids/boronates including primary, secondary, and tertiary as well as (hetero)aryl acetylenic bromides with diverse functional groups and affording the desired internal alkynes (57 examples) in good to excellent yields. The synthetic utility of this approach is further demonstrated through the late-stage functionalization of several medicinally relevant compounds. Additionally, the method's practicality was confirmed by successfully scaling up the reaction to gram-scale quantities. Preliminary mechanistic investigations suggest that photoirradiation of acetylenic bromides generates bromine radicals in situ, which play a key role in producing aminyl radicals that activate alkylboronic acids or boronates through a radical transfer process.
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