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Sodium borohydride, also known as sodium tetrahydridoborate and sodium tetrahydroborate, [5] is an inorganic compound with the formula Na B H 4 (sometimes written as Na[BH 4]). It is a white crystalline solid, usually encountered as an aqueous basic solution .
The Narasaka–Prasad reduction, sometimes simply called Narasaka reduction, is a diastereoselective reduction of β-hydroxy ketones to the corresponding syn-dialcohols. The reaction employs a boron chelating agent, such as BBu 2 OMe, and a reducing agent, commonly sodium borohydride. This protocol was first discovered by Narasaka in 1984. [1]
Enantioselective ketone reductions convert prochiral ketones into chiral, non-racemic alcohols and are used heavily for the synthesis of stereodefined alcohols. [ 1 ] Carbonyl reduction, the net addition of H 2 across a carbon-oxygen double bond, is an important way to prepare alcohols.
Sodium triacetoxyborohydride is a milder reducing agent than sodium borohydride or even sodium cyanoborohydride. It reduces aldehydes but not most ketones. It is especially suitable for reductive aminations of aldehydes and ketones. [2] [3] [4]
The Luche reduction can be conducted chemoselectively toward ketone in the presence of aldehydes or towards α,β-unsaturated ketones in the presence of a non-conjugated ketone. [5] An enone forms an allylic alcohol in a 1,2-addition, and the competing conjugate 1,4-addition is suppressed.
In addition to their reduction to alcohols, aldehydes and ketones can be converted to amines, i.e., reductive amination. [18] Because of its cyano substituent, NaBH 3 CN is a weak reducer at moderate pH (>4), so it preferentially reduces iminium cations that exist in the presence of carbonyls:
The use of triphenylphosphine, thiourea, zinc dust, or dimethyl sulfide produces aldehydes or ketones. While the use of sodium borohydride produces alcohols. (R group can also be hydrogens) The use of hydrogen peroxide can produce carboxylic acids. Amine N-oxides produce aldehydes directly. [8]
Ketone reduction via sodium borohydride. Items portrayed in this file depicts. ketone. carbonyl. carbonyl reduction. sodium borohydride. creator. some value.