Studies of microwave-enhanced Suzuki–Miyaura vinylation of electron-rich sterically hindered substrates utilizing potassium vinyltrifluoroborate

• Published in: Tetrahedron letters 2010-12, Vol.51 (51), p.6748-6752
• Main Authors: Brooker, Matthew D., Cooper, Stefan M., Hodges, Dena R., Carter, Rhiannon R., Wyatt, Justin K.
• Format: Article
• Language: English
• Subjects: Derivatives; Hindered aryl bromides; Irradiation; Joining; Microwaves; Optimization; Palladium catalysis; Potassium; Potassium vinyltrifluoroborate; Solvents; Styrenes; Suzuki–Miyaura; Tetrahedrons
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2010.10.087

The Suzuki–Miyaura cross-coupling of sterically hindered and electron-rich ortho, ortho′-substituted aryl halides with potassium vinyltrifluoroborate utilizing microwave irradiation has been conducted while adjusting solvent ratio, irradiation time, and catalyst loading to find optimal conditions. Coupling of benzyl 3,5-bis(benzyloxy)-4-bromobenzoate leads to a mixture of the desired styrene derivative, and the reduced product. 4-Bromo-1,3,5-trimethoxybenzene, methyl 4-bromo-3,5-dimethoxybenzoate, and mesitylene bromide were also coupled to test the breadth and scope of this methodology. Of these substrates tested only 4-bromo-1,3,5-trimethoxybenzene was not vinylated successfully, which is believed to be due to the electron-rich nature of this system. The Suzuki–Miyaura cross-coupling of sterically hindered and electron-rich ortho, ortho′-substituted aryl halides with potassium vinyltrifluoroborate utilizing microwave irradiation has been conducted while adjusting solvent ratio, irradiation time, and catalyst loading to find optimal conditions. Coupling of benzyl 3,5-bis(benzyloxy)-4-bromobenzoate leads to a mixture of the desired styrene derivative and the reduced product. 4-Bromo-1,3,5-trimethoxybenzene, methyl 4-bromo-3,5-dimethoxybenzoate, and mesitylene bromide were also coupled to test the breadth and scope of this methodology. Of these substrates tested only 4-bromo-1,3,5-trimethoxybenzene was not vinylated successfully, which is believed to be due to the electron-rich nature of this system.