Potassium tri-s-butylborohydride

Regeneratable polymeric organotin dihydride beads have been used to reduce halides selectively (e.g. 3-bromocamphor to camphor).52 /3-Unsubstituted cyclohex-enones undergo exclusive and almost quantitative 1,4-reduction by potassium tri-s-butylborohydride to the corresponding saturated ketone [e.g. (16)] 53 reductive alkylation of carvone proceeds similarly to (17 R = Me, X = H).53 In contrast,... 

In the course of investigations involving the reaction of lithium triethylhydroborate with conjugated nitroalkenes (61),A -ethylamines (62) were consistently observed as by-products (equation 34). The intermediacy of nitroso compounds has been confirmed in this reaction which provides a useful method for the preparation of A -ethylated amine derivatives. These A -alkylated products are not produced when sterically demanding reagents, such as potassium tri-s-butylborohydride, are used. Apparently, the competition between reduction and alkylation of the nitroso group is sensitive to steric effects. 

Trialkyl borohydrides such as Lithium Tri-s-butylborohydride and Potassium Tri-s-butylborohydride are superior reagents for the chemoselective 1,4-reduction of enones. On the other hand, 1,2-reduction can be obtained by using NaBHj in the mixed solvent MeOH-THF (1 9), or with NaBHj in combination with CeCH or other lanthanide salts. ... 

Cyclohexenones which are unsubstituted at the p-vinylic carbon have been found to undergo 1,4-reduction and reductive alkylation with potassium tri-s-butylborohydride in tetrahydrofuran at 195 K with a high selectivity for the less stable isomer, as found for other sterically hindered reductants 2-cyclohexenone gave 95 % yield of the substituted cyclohexanone. If more than two equivalents of the borohydride are present and the reation is quenched with water at 195 K, only saturated alcohols result. 

The use of 2,4,6-tri-isopropylbenzenesulphonylhydrazides (in place of the tosylhydrazide) allows milder conditions to be used for the preparation of aromatic aldehydes by the McFadyen-Stevens reaction. Addition of hydrazine hydrate and traces of cupric sulphate suppresses formation of aromatic ester and alcohol by-products. Reduction of oxazolinium salts by sodium borohydride, as part of the well known sequence for the conversion of carboxylic acids into aldehydes, can lead to ring cleavage to form amino-alcohols. It is now reported that over-reduction is much less marked if potassium tri-s-butylborohydride is used as reducing agent (Scheme 2) ... 

The utility of lithium and potassium tri-s-butylborohydrides and lithium triethyl-borohydride as reagents for the conjugate reduction and reductive alkylation of unsaturated ketones and esters has been surveyed. ... 

Phenolic oxidation of the diphenolic amide 285 using potassium ferric (III) cyanide afforded (-l-)-iV-formyldibromonarwedine (286), which was reduced successively with lithium tri-s-butylborohydride (L-Selectride) and with LiAlH4 to afford ( )-261. Resolution of ( )-261 using rf-camphoric acid provided (-)- and (-l-)-galanthamines (261) through the camphanate derivatives 287 and 288 165) (Scheme 30). 

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