Sodium cyanoborohydride

Sodium cyanoborohydride is the chemical compound with the formula NaBH₃CN. It is a colourless salt, but commercial samples can appear tan. It is widely used in organic synthesis for the reduction of imines. The salt tolerates aqueous conditions.[2]

Sodium cyanoborohydride

Names
Other names Sodium cyanotrihydridoborate
Identifiers
CAS Number	25895-60-7^Y
3D model (JSmol)	Interactive image
ECHA InfoCard	100.043.001
EC Number	247-317-2
PubChem CID	5003444
UNII	C4I8C58P9T^Y
CompTox Dashboard (EPA)	DTXSID40894864
InChI InChI=1S/CH3BN.Na/c2-1-3;/h2H3;/q-1;+1
SMILES [BH3-]C#N.[Na+]
Properties
Chemical formula	NaBH3CN
Molar mass	62.84 gmol^−1
Appearance	white to off-white powder, hygroscopic
Density	1.20 g/cm^3
Melting point	241 °C (466 °F; 514 K) decomposes
Solubility in water	212 g/100 mL (29 °C)
Solubility	soluble in diglyme, tetrahydrofuran, methanol slightly soluble in methanol insoluble in diethyl ether
Hazards
Main hazards	Fatal if swallowed, in contact with skin or if inhaled Contact with acids liberates very toxic gas Contact with water liberates highly flammable gas
Safety data sheet	Sigma Aldrich[1]
GHS pictograms
GHS Signal word	Danger
GHS hazard statements	H228, H300, H310, H330, H314, H410
GHS precautionary statements	P210, P260, P264, P273, P280, P284
NFPA 704 (fire diamond)	3 4 2
Threshold limit value (TLV)	5 mg/m3 (TWA)
Related compounds
Other anions	Sodium borohydride
Related compounds	Lithium aluminium hydride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is ^YN ?)
Infobox references

Use

Owing to the presence of the electron-withdrawing cyanide substituent, [B(CN)H₃]⁻ is far less reducing than is [BH₄]⁻, as found in sodium borohydride.[3] As a mild reducing agent, it is especially used to convert imines to amines.

It is especially favored for reductive aminations, wherein aldehydes or ketones are treated with an amine in the presence of this reagent:

R₂CO + R'NH₂ + NaBH₃CN + CH₃OH → R₂CH-NHR' + "NaCH₃OBH₂CN"

The reagent is typically used in excess. Selectivity is achieved at mildly basic solutions (pH 7-10). The reagent is ideal for reductive aminations ("Borch Reaction").[4] In conjunction with tosylhydrazine, sodium cyanoborohydride is used in the reductive deoxygenation of ketones.[2]

Structure and preparation

The tetrahedral anion BH₃(CN)⁻ comprises the salt.

The reagent is invariably purchased, although it can be prepared easily. One method involves combining sodium cyanide and borane. Another route entails treating sodium borohydride with mercury(II) cyanide. The commercial samples can be purified but the yields of the reductive aminations do not improve.[5]

See also

• Sodium triacetoxyborohydride - a milder reductant, but unstable in water
• Sodium borohydride - a stronger, cheaper reductant

References

1. Sigma-Aldrich Co., Sodium cyanoborohydride. Retrieved on 2014-11-09.
2. Robert O. Hutchins, MaryGail K. Hutchins, Matthew L. Crawley (2007). "Sodium Cyanoborohydride". Encyclopedia of Reagents for Organic Synthesis. John Wiley & Sons. doi:10.1002/047084289X.rs059.pub2.CS1 maint: uses authors parameter (link)
3. Ellen W. Baxter, Allen B. Reitz Reductive Aminations of Carbonyl Compounds with Borohydride and Borane Reducing Agents in Organic Reactions, 2002, John Wiley and Sons. doi:10.1002/0471264180.or059.01
4. Richard F. Borch (1988). "Reductive Amination with Sodium Cyanoborohydride: N,N-Dimethylcyclohexylamine". Organic Syntheses.; Collective Volume, 6, p. 499
5. Richard F. Borch and Mark D. Bernstein and H. Dupont Durst (1971). "Cyanohydridoborate Anion as a Selective Reducing Agent". J. Am. Chem. Soc. 93 (12): 2897–2904. doi:10.1021/ja00741a013.