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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. Sodium borohydride is a reducing agent that finds application in papermaking and dye ...
Since, aldehydes reduce more easily than ketones, they require milder reagents and milder conditions. At the other extreme, carboxylic acids, amides, and esters are poorly electrophilic and require strong reducing agents. [17] The idealized equation for the reduction of a ketone by sodium borohydride is: 4 RCOR' + NaBH 4 → NaB(OCHRR') 4
Some amides can be reduced to aldehydes in the Sonn-Müller method, but most routes to aldehydes involve a well-chosen organometallic reductant. Lithium aluminum hydride reduces an excess of N,N-disubstituted amides to an aldehyde: [citation needed] R(CO)NRR' + LiAlH 4 → RCHO + HNRR' With further reduction the alcohol is obtained.
STAB is a weaker reductant than NaBH 4, and can preferentially reduce the imine group in the presence of other reduction-sensitive functional groups. While STAB has also been reported as a selective reducing agent for aldehydes in the presence of keto groups, standard reductive amination reaction conditions greatly favour imine reduction to ...
For example, sodium cyanoborohydride is generally incapable of reducing amides, ethers, esters and lactones, nitriles, or epoxides. [8] Therefore, it can selectively reduce some functionalities in the presence of others. Some examples of selective reduction include: Reduction of iminium ions in the presence of carbonyls [8]
The mechanism for the reduction of a nitrile to an aldehyde with DIBAL-H. The hydride reagent Diisobutylaluminium hydride, or DIBAL-H, is commonly used to convert nitriles to the aldehyde. [14]
Weinreb and Nahm originally proposed the following reaction mechanism to explain the selectivity shown in reactions of the Weinreb–Nahm amide. Their suggestion was that the tetrahedral intermediate (A below) formed as a result of nucleophilic addition by the organometallic reagent is stabilized by chelation from the methoxy group as shown. [1]
The sodium borohydride method obeys the following stoichiometry: NaBH 4 + 8 NaOH + 8 SO 2 → 4 Na 2 S 2 O 4 + NaBO 2 + 6 H 2 O. Each equivalent of H − reduces two equivalents of sulfur dioxide. Formate has also been used as the reductant.