Benzylic bromination catalyzed by triphenylphosphine selenide via Lewis basic activation. Issue 30 (26th July 2017)

• Record Type: Journal Article
• Authors: Ayonon, Arianna; Nalbandian, Christopher; Guillemard, Lucas; Gustafson, Jeffrey
• Is Part Of: Tetrahedron letters. Volume 58:Issue 30(2017)
• Page Start: 2940
• Page End: 2943
• Publication Date: 2017-07-26
• Subjects: Triphenylphosphine selenide -- Benzyl bromides -- Phthalides -- Lewis base catalysis; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tetlet.2017.06.042
• Languages: English
• ISSNs: 0040-4039

Abstract

Graphical abstract: The synthesis of benzyl bromides was achieved under mild reaction conditions using N -bromosuccinimide as a bromine source and triphenylphosphine selenide as a catalyst. These conditions were compatible with a variety of substrates including boronic esters, protected amines to give imines, and carboxylic acids (to give phthalides when ortho to the benzylic center). A preliminary mechanistic investigation utilizing calculated bond dissociation energies (BDE) is employed to rationalize how a Lewis base can activate a radical mechanism. Highlights: Lewis bases were found to catalyze benzylic brominations at room temperature. Overall 13 diverse substrates were evaluated. Phthalides and Imines are easy to access with this chemistry. Operationally simple and mild. Abstract: The synthesis of benzyl bromides was achieved under mild reaction conditions using N -bromosuccinimide as a bromine source and triphenylphosphine selenide as a catalyst. These conditions were compatible with a variety of substrates including boronic esters, protected amines to give imines, and carboxylic acids (to give phthalides when ortho to the benzylic center). A preliminary mechanistic investigation utilizing calculated bond dissociation energies (BDE) is employed to rationalize how a Lewis base can activate a radical mechanism.