Sodium cyanoborohydride

Sodium cyanoborohydride
Other names Sodium cyanotrihydridoborate
Identifiers
CAS number	25895-60-7 Y
PubChem	24849595
EC number	247-317-2
Properties
Molecular formula	NaBH3CN
Molar mass	62.84 g/mol
Appearance	white to off-white powder, hygroscopic
Density	1.20 g/cm3
Melting point	241 °C decomp.
Solubility in water	soluble
Hazards
MSDS	External MSDS
EU Index	not listed
NFPA 704	2 3 2 W
Related compounds
Other anions	Sodium borohydride
Related compounds	Lithium aluminium hydride
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Sodium cyanoborohydride is the inorganic compound with the formula NaBH₃(CN). This colourless salt is widely used in organic synthesis for the reduction of imines.

Preparation and use

The reagent may be prepared, either by treating sodium cyanide with borane, or by reacting sodium borohydride with mercury(II) cyanide. Owing to the presence of the electron-withdrawing cyanide substituent, [B(CN)H₃]⁻ is far less nucleophilic than is [BH₄]⁻, as found in sodium borohydride.^[1]

Sodium cyanoborohydride is a mild reducing agent that converts imines to amines. It can be used to exchange the oxygen for an amine group on the carbonyl carbon of aldehydes or ketones when reacted with ammonia or a primary amine. Selectivity is achieved at mildly basic solutions (pH 7-10). Owing to this selectivity, the reagent is ideal for reductive aminations. This reduction is known sometimes as the Borch Reaction.^[2] The salt is mildly water-sensitive, but tolerates aqueous conditions.^[3] In addition, sodium cyanoborohydride is often used in hydrogenolysis reactions, such as the opening of acetals.

References

1. ^ 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
2. ^ 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. 
3. ^ Timothy M. Beard and Nicholas J. Turner (2002). "Deracemisation and Stereoinversion of alpha-Amino Acids Using D-Amino Acid Oxidase and Hydride Reducing Agents". Chemical Communications (3): 246–7.