Cross-Coupling between Arylboronic Acids and Terminal Alkynes in Water Microdroplets
Sandeep Bose, Mohammad Mofidfar, Richard N. Zare, Elumalai Gnanamani
Abstract
We report a cross-coupling reaction between terminal alkyne and arylboronic acid to form the C–C bond in water microdroplets under mild, catalyst-free conditions. A solution containing phenylacetylene (50 μM) and 4-methoxyphenylboronic acid (50 μM) in a 4:1 (H 2 O: ACN) mixture was electrosprayed at +1.5 kV, and the reaction products were analyzed using a mass spectrometer (MS). We observed C(sp 2 )-C(sp) coupling reaction products within milliseconds, which were characterized by tandem mass spectrometry (MS 2 ). Based on in situ reaction studies and radical experiments, we determined the reaction mechanism for the coupling reaction. Our approach offers a sustainable and environmentally benign pathway for the synthesis of internal aryl alkynes, making it a suitable building block for the preparation of various pharmaceutical drugs.