Hydroboration of isocyanates: cobalt-catalyzedvs.catalyst-free approaches

Abstract

Hydroboration of isocyanates with HBPin was demonstrated using both catalytic and catalyst-free approaches. In arene solvents, reactions employed the commercially available and bench-stable Co(acac)2/dpephos (dpephos = bis[(2-diphenylphosphino)phenyl] ether) pre-catalyst and...

NHC-Silyliumylidene Cation-Catalyzed Hydroboration of Isocyanates with Pinacolborane

“…In these catalysis reactions, the activity of catalyst 1 in terms of TOF and product yield are better than that of other metal catalysts such as β-diketiminato magnesium, bis­(guanidinate) aluminum and zinc dihydride complexes, , AgSbF 6 , and Co­(acac) 2 (for example, 4m , [Zn]: yield = > 99%, TOF = 4.17 h –1 ; [Al]: yield = > 99%, TOF = 4.17 h –1 ; [Co]: yield = 91%, TOF = 0.95 h –1 ; see Table S4).…”

Magnesium halide-catalyzed hydroboration of isocyanates and ketones

“…11–27 Compared with alkene (CC), alkyne (CC) and nitrile (CN) unsaturated bonds, reports on metal-catalyzed hydroboration of isocyanates are very few. 28–35 In 2021, Nembenna et al . reported that a remarkable conjugated bis-guanidinate supported zinc hydride was employed as an efficient catalyst in the hydroboration of a range of aryl and alkyl isocyanates to afford selectively N -boryl formamide, bis(boryl) hemiaminal and N -boryl methyl amine products, respectively.…”

“…[11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] Compared with alkene (CvC), alkyne (CuC) and nitrile (CuN) unsaturated bonds, reports on metal-catalyzed hydroboration of isocyanates are very few. [28][29][30][31][32][33][34][35] In 2021, Nembenna et al reported that a remarkable conjugated bisguanidinate supported zinc hydride was employed as an efficient catalyst in the hydroboration of a range of aryl and alkyl isocyanates to afford selectively N-boryl formamide, bis (boryl) hemiaminal and N-boryl methyl amine products, respectively. 28 Nevertheless, to the best of our knowledge, there have been only three examples of Mg-catalyzed hydroboration of isocyanates so far.…”

Carbodiimide and Isocyanate Hydroboration by a Cyclic Carbodiphosphorane Catalyst**

“…[9,29] Subsequent work has revealed a range of catalysts for the selective hydrodeoxygenation of isocyanates at 50-100 °C. [24,[30][31][32][33][34][35][36][37][38] The monohydroboration of isocyanates has also been observed at long reaction times under catalyst-free conditions [35] or using transition metal, [12,33,35,39] main group, [23,24,30,32,34,38,40] and actinide [37] catalysts. However, notably, none of the existing catalysts for carbodiimide or isocyanate hydroboration are neutral, Lewis basic organocatalysts.…”

“…Initial studies of catalytic isocyanate hydroboration reactions in 2016 and 2017 reported magnesium catalysts for the dihydroboration of isocyanates to form N , O ‐bis(boryl) hemiaminal products or hydrodeoxygenation reactions to generate N ‐methyl amines [9,29] . Subsequent work has revealed a range of catalysts for the selective hydrodeoxygenation of isocyanates at 50–100 °C [24,30–38] . The monohydroboration of isocyanates has also been observed at long reaction times under catalyst‐free conditions [35] or using transition metal, [12,33,35,39] main group, [23,24,30,32,34,38,40] and actinide [37] catalysts.…”