Iron‐Catalyzed, Atom‐Economical, Chemo‐ and Regioselective Alkene Hydroboration with Pinacolborane

A Cobalt‐Catalyzed Alkene Hydroboration with Pinacolborane

“…In our previous report, we showed that the Fe precatalyst 1 , upon activation with NaBHEt 3 , is efficient in the hydroboration of aliphatic α‐olefins (Table 1, entry 2). For vinylarenes, however, the hydroboration process was accompanied by a dehydrogenative borylation to form vinylboronate (Table 1, entry 1) 10a. The catalysis with the new Fe complex [( i Pr PNN)FeCl 2 ] ( 4 ) led to similar results.…”

(N‐Phosphinoamidinate)cobalt‐Catalyzed Hydroboration: Alkene Isomerization Affords Terminal Selectivity

“…Catalysts based on comparatively abundant first-row transition metals, including iron [5,6] and cobalt, represent attractive candidates in this regard.Some progress has been made as of late with regard to the development of iron catalysts for alkene hydroboration. Notable achievements include the addition of pinacolborane (HBPin) to conjugated dienes, [7] terminal alkenes including unactivated olefins and styrene, [8][9][10][11] as well as cyclic aliphatic alkenes, [9] where relevant with anti-Markovnikov selectivity and including examples that proceed at room temperature in the absence of added solvent. The key role of ancillary ligand design in enabling such reactivity is established in these reports, with appropriately substituted tridentate bis-(imino)pyridine [9] and bipyridylphosphine [8] ligands, as well as photochemically activated (NHC)Fe(CO) 4[10] pre-catalysts proving effective.…”

“…Notable achievements include the addition of pinacolborane (HBPin) to conjugated dienes, [7] terminal alkenes including unactivated olefins and styrene, [8][9][10][11] as well as cyclic aliphatic alkenes, [9] where relevant with anti-Markovnikov selectivity and including examples that proceed at room temperature in the absence of added solvent. The key role of ancillary ligand design in enabling such reactivity is established in these reports, with appropriately substituted tridentate bis-(imino)pyridine [9] and bipyridylphosphine [8] ligands, as well as photochemically activated (NHC)Fe(CO) 4 [10] pre-catalysts proving effective. However, a number of important substrate scope limitations have been encountered to date in iron-catalyzed hydroboration chemistry; efficient transformations involving linear internal aliphatic alkenes have proven to be a considerable challenge, with reports of such reactivity being limited to a small number of examples, whereby high conversion but poor regiochemistry is achieved.…”

Iron‐Catalysed Hydrofunctionalisation of Alkenes and Alkynes

“…[143] It was also reported that FeCl 3 would catalyse the hydromagnesiation of styrene (105), albeit in only 15 % yield (Scheme 60 A, 51 % yield using TiCl 4 ).…”

“…[105] A number of iron(II) dihalide pre-catalysts 209, which were activated in situ using NaHBEt 3 (3 equiv. with respect to iron), were investigated for the addition of pinacol borane to terminal alkenes.…”