Potassium triisopropoxyborohydride

Homologation of boronic esters. The reagent 1 can be formed in situ by reaction of CH2C12 with lithium 2,2, 6,6 -tetramethylpiperidide (LiTMP) or even LDA. The product obtained on reaction of 1 with alkylboronic esters, an a-chlo-roboronic ester, is reduced by potassium triisopropoxyborohydride (KIPBH) to the homologated boronic ester.1... 

Asymmetric reactions of oc-keto esters of ( —)-l. Reduction of the a-keto ester (2) of (- )-8-phenylmenthol (1) with potassium triisopropoxyborohydride proceeds in 90% de to give the lactate ester (R)-3 with chirality opposite to that obtained by reaction of... 

Potassium triisopropoxyborohydride, 5, 565 9, 393. As originally prepared, K(0-i-Pr),BH contains an impurity, probably KiO-(-Pr)4B. Essentially pure reagent can be prepared by reaction of (0-(-Pr),B with excess KH in refluxing THE. It should be stored over a small amount of KH to prevent disproportionation. This material provides essentially quantitative yields in the hydridation ol thexylBR CI in the presence of a second olefin to form thexylBR R . 

Carbonylation of organoboranes (2, 60 3, 41-42). Potassium triisopropoxyborohydride is superior to other hydrides for this reaction. 9-Alkyl-9-BBN derivatives are excellent substrates, since the 9-alkyl groups are utilized in almost quantitative yield. ... 

Potassium triisopropoxyborohydride, a mild selective reducing agent, rapidly converted ketones and aldehydes to the corresponding alcohols, while many common functional groups were inert.The reaction of potassium hydride with triphenylborane produced the triphenylborohydride, which is highly hindered and which exhibited excellent chemoselectivity between ketones. Cyclohexanone was reduced in preference to cyclopentanone (97 3) and 4-heptanone (99.4 0.6), while methyl ketones were more reactive than 4-heptanone (2-heptanone, 94 6 acetophenone, 97.8 2.2). 

When the reaction between a trialkylborane and carbon monoxide (18-23) is carried out in the presence of a reducing agent such as lithium borohydride or potassium triisopropoxyborohydride, the reduction agent intercepts the intermediate 89, so that only one boron-to-carbon migration takes place, and the product is hydrolyzed to a primary alcohol or oxidized to an aldehyde." This procedure wastes two of the three R groups, but this problem can be avoided by the use of... 

Z)-1-Alkenylboronates are prepared by hydroboration of 1-bromo-l-alkynes with dibromoborane/dimethyl sulfide complex, followed by treatment of the intermediate (Z)-(l-bromo-l-alkenyl)boronates with potassium triisopropoxyborohydride. H. C. Brown and T. Imai, Organometallics, 1984, 3, 1392. 

Chloromethylation of 2-alkyl-1,3,2-dioxaborinancs with dichloromethyllithium followed by reduction with potassium triisopropoxyborohydride yields one-carbon-homologated boronic esters. The homologation can be repeated and the homologated esters transformed into the corresponding at-, j7- or -/-chiral alcohols, aldehydes and acids13. 

An alternative route to vinylborinates adds the dimethyl sulfide complex of HBBr2 to 1-bromo-l-alkynes. Reaction of 1-bromo-l-hexyne (52) gave 53 in 87% yield, after treatment with an alcohol (2-propanol in this case).Subsequent reduction of the bromide with potassium triisopropoxyborohydride [KBH(0/-Pr)3] generated cis-vinylborane (54) in 89% yield. 

Related Reagents. Cerium(III) Chloride Nickel Boride Potassium Triisopropoxyborohydride Sodium Cyanoboro-hydride Sodium Triacetoxyborohydride Cobalt Boride Lithium Borohydride Lithium Aluminium Hydride Zinc Borohydride Tetramethylammonium Triacetoxyborohydride. 

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