Zinc borohydride zn(BH).
English Name】 Zinc Borohydride
Molecular Formula】 B h Zn
Molecular weight] 9509
CAS Number] 17611-70-0
Physical Properties] Soluble in ethanol, methylene chloride, toluene, DMF and THF.
Preparation and Commodities] Zinc borohydride reagent needs to be prepared by in-situ reaction, using anhydrous zinc oxide and sodium boride oxide in anhydrous ether solvent.
Precautions] Ether solution of zinc borooxide is sensitive to moisture and should be stored and used under the protection of inert gas.
Zinc borohydride is a mild reducing reagent that is particularly suitable for substrates containing base-sensitive functional groups. At the same time, it is also a stereoselective reducing reagent.
Zinc borohydride is a mild carbonyl compound reduction reagent, which can realize the reduction reaction of aldehydes, ketones and methylimines under ordinary conditions to obtain the corresponding alcohol. Because the ether solution of zinc borohydride is neutral, it is very suitable for substrates containing alkali-sensitive functional groups such as cyano, ester, and -lactoneAnd in the case of the coexistence of saturated ketones and unsaturated ketones, the reduction of saturated ketones can be selectively and preferentially realized.
Ordinary carboxylic acids or esters are not reduced by zinc borohydride, but active esters or thioeesters can be efficiently converted into their respective alcohols. The use of ultrasound can also promote the reduction of inactive aliphatic carboxylates.
Asymmetric epoxy compounds are capable of asymmetric ring-opening reactions under silica-supported zinc borohydride, with cleavage occurring at one end of the C-O bond with fewer substituents.
Under the action of zinc borohydride, tertiary halide and pyrene halide compounds can undergo reductive dehalogenation reaction.
Under the action of zinc borohydride, -methyl-hydroxy ester compounds can achieve stereoselective reduction reactions. When there is a conjugation effect between the carbonyl group and the vinyl or phenyl group, the stereoselectivity of the reduction reaction is better.
Under the action of zinc borohydride, -hydroxy ketone can stereoselectively obtain trans-diol reduction products. When R is a phenyl group or R is a group with a large stereosteric hindrance, the stereoselectivity obtained is better.
Excerpted from: "Modern Organic Synthesis Reagents - Reduction Reaction Reagents", edited by Hu Yuefei.