Sodium cyanoborohydride

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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]




Contents





  • 1 Use


  • 2 Structure and preparation


  • 3 See also


  • 4 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. ^ ab 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).mw-parser-output cite.citationfont-style:inherit.mw-parser-output .citation qquotes:"""""""'""'".mw-parser-output .citation .cs1-lock-free abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-limited a,.mw-parser-output .citation .cs1-lock-registration abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .citation .cs1-lock-subscription abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registrationcolor:#555.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration spanborder-bottom:1px dotted;cursor:help.mw-parser-output .cs1-ws-icon abackground:url("//upload.wikimedia.org/wikipedia/commons/thumb/4/4c/Wikisource-logo.svg/12px-Wikisource-logo.svg.png")no-repeat;background-position:right .1em center.mw-parser-output code.cs1-codecolor:inherit;background:inherit;border:inherit;padding:inherit.mw-parser-output .cs1-hidden-errordisplay:none;font-size:100%.mw-parser-output .cs1-visible-errorfont-size:100%.mw-parser-output .cs1-maintdisplay:none;color:#33aa33;margin-left:0.3em.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-formatfont-size:95%.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-leftpadding-left:0.2em.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-rightpadding-right:0.2em


  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.



Sodium cyanoborohydride

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


  • 20587905





Properties

Chemical formula

NaBH3CN

Molar mass
62.84 gmol−1
Appearance
white to off-white powder, hygroscopic

Density
1.20 g/cm3

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-pictogram-flamme.svgGHS-pictogram-acid.svgGHS-pictogram-skull.svg

GHS signal word
Danger

GHS hazard statements


H228, H300, H310, H330, H314, H410

GHS precautionary statements


P210, P260, P264, P273, P280, P284

NFPA 704



Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasolineHealth code 4: Very short exposure could cause death or major residual injury. E.g., VX gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorusSpecial hazards (white): no codeNFPA 704 four-colored diamond

3


4


2




Threshold limit value

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).


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Infobox references





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