Metal-mediated reactions of bromoform with electron-rich and electron-deficient carbon-carbon and carbon-hetero atom multiple bonds

Magnesium-Mediated Regioselective Additions of Bromoform to Quinone Methides and Aurone-Derived Azadienes

“…The reaction of haloform with alkenes for the generation of polyhalomethylated and dihalocyclopropane derivatives under anionic (base/PTC) [8][9][10] and radical 11 conditions is well explored, but the metal-mediated bromoform addition remained relatively obscure. 12 We and others have been involved in the application of Mg-CHBr3 as a convenient reagent system for addition of CBr3 group to various electron-deficient alkenes. 12 Thus, the reaction of bromoform in the presence of magnesium with nitroalkenes, 13 chalcones, 14 sulfonyl/Boc imines, 15 nitrodienes, 16 and open-chain dibenzylideneketones 16 primarily affords CBr3 adducts via conjugate addition which depending on the reaction conditions can be further selectively transformed to dibromomethylidenes, 13 cyclic orthoesters and γketoesters.…”

“…12 We and others have been involved in the application of Mg-CHBr3 as a convenient reagent system for addition of CBr3 group to various electron-deficient alkenes. 12 Thus, the reaction of bromoform in the presence of magnesium with nitroalkenes, 13 chalcones, 14 sulfonyl/Boc imines, 15 nitrodienes, 16 and open-chain dibenzylideneketones 16 primarily affords CBr3 adducts via conjugate addition which depending on the reaction conditions can be further selectively transformed to dibromomethylidenes, 13 cyclic orthoesters and γketoesters. 14 On the other hand, cycloalkanone derived chalcones, 17 cyclic dibenzylideneketones 16 as well as 3-olefinic oxindoles 16 furnished spiro-cyclopropanated products which underwent Lewis acid-catalyzed regioselective ring expansion to afford fused bromofurans via Cloke-Wilson rearrangement.…”