Two dimensional inorganic electride-promoted electron transfer efficiency in transfer hydrogenation of alkynes and alkenes

A simple and highly efficient transfer hydrogenation of alkynes and alkenes by using a two-dimensional electride, dicalcium nitride ([Ca2N]+·e–), as an electron transfer agent is disclosed.


Synthesis of dicalcium nitride [Ca 2 N] + •e  electride
A stoichiometric polycrystalline dicalcium nitride ([Ca 2 N] + •e  ) was synthesized by the solid-state reaction of calcium nitride(Ca 3 N 2 ) powders and calcium metals. Mixture of Ca 3 N 2 powders and calcium chips at a molar ratio of 1:1 were pressed into a pellet form under pressure (20~30 MPa). The pellet was fully covered with molybdenum foil and annealed at 800 o C for 48 hrs under vacuum (~10 3 Pa). Then, the sample was quenched into water. To improve homogeneity of dicalcium nitride [Ca 2 N] + •e  , the synthesized sample was ground into a powder in an agate mortar in nitrogen-filled glovebox and re-annealed under the same conditions.

General procedure for transfer hydrogenation of aromatic alkynes
Dicalcium nitride [Ca 2 N] + •e  (235 mg, 2.5 mmol) was added to a suspension of alkyne (0.5 mmol) in 4 ml of dry DMF and iPrOH in 1:1 mixture at room temperature. The reaction was stirred until color change of electride(black → white) indicated complete consumption of the starting material, and then the reaction mixture was quenched with water and 5% HCl solution in water and, extracted with Et 2 O (15 mL×3), and remove the DMF by washing with DI water. The combined organic layers were dried over MgSO 4 and concentrated under vacuum.

General procedure for transfer hydrogenation of aromatic alkenes
Dicalcium nitride [Ca 2 N] + ·e  (144 mg, 1.5 mmol) was added to a solution of alkene (0.5 mmol) in 4 mL of dry DMF and MeOH in 1:1 mixture at room temperature. The reaction was stirred until color change of electride from black to white, indicating that the starting material was completely consumed. Upon completion of the reaction, the reaction mixture was quenched with water and washed with aqueous 5% HCl solution. The reaction mixture was extracted with Et 2 O (15 mL × 3) and saturated brine. The combined extracts were dried over anhydrous MgSO 4 , filtered, and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel to furnish the corresponding product.

1a'
The physical and spectral data were identical to those previously reported for this compound.

1b'
The physical and spectral data were identical to those previously reported for this compound.

1c'
The physical and spectral data were identical to those previously reported for this compound. 3

1d'
The physical and spectral data were identical to those previously reported for this compound.

1e'
The physical and spectral data were identical to those previously reported for this compound.  The physical and spectral data were identical to those previously reported for this compound.

1,2-bis(4-fluorophenyl)ethane (Table 3, Entry 8)
The physical and spectral data were identical to those previously reported for this compound.

1i'
The physical and spectral data were identical to those previously reported for this compound. 6

2c'
The physical and spectral data were identical to those previously reported for this compound.

2d'
The physical and spectral data were identical to those previously reported for this compound. 8