Potassium triethylborohydride

Potassium triethylborohydride, 260 Sodium borohydride, 21 Ring-forming reactions 2,2 -Dihydroxy-1,1 -binaphthyl, 113 Other asymmetric reactions Camphor-10-sulfonic acid, 62 Di-jjL-chlorobis(l,5-cyclooctadiene)di-rhodium-2,3-0-Isopropylidene-2,3-dihydroxy-1,4-bis(diphenyl-phosphine)butane, 153... 

Potassium triethylborohydride, 260 Samarium(II) iodide, 270 Sodium-Alcohol, 277 Sodium borohydride, 21, 167 Sodium cyanoborohydride-Tin(II) chloride, 280... 

Lithium borohydride, 92 (lR,2S)-N-Methylephedrine-0-pro-pionate, 308 Norephedrine, 200 2-Oxazolidones, chiral, 225 (2R,4R)-Pentanediol, 237 Potassium triethylborohydride, 260 Other hydroxy carbonyl compounds (R)-( + )- and (S)-( - )-2,2 -Bis-(diphenylphosphine)-1,1 -binaphthyl, 36 Ketones... 

Dimethylphenylsilane, 123 2-Oxazolidones, chiral, 225 Potassium triethylborohydride, 260 Hydroxy esters and lactones a-Hydroxy esters and lactones By hydroxylation a to the carbonyl group... 

Organocopper reagents-Boron trifluoride etherate, 208 9-(Phenylseleno)-9-borabicyclo-[3.3. ljnonane, 245 B-3-Pinanyl-9-borabicyclo-[3.3.ljnonane, 249 Potassium triethylborohydride, 260... 

Stereoselective reduction of a-alkyl-3-keto acid derivatives represents an attractive alternative to stereoselective aldol condensation. Complementary methods for pr uction of either diastereoisomer of a-alkyl-3-hydroxy amides from the corresponding a-alkyl-3-keto amides (53) have been developed. Zinc borohydride in ether at -78 C gave the syn isomer (54) with excellent selectivity ( 7 3) in high yield via a chelated transition state. A Felkin transition state with the amide in the perpendicular position accounted for reduction with potassium triethylborohydride in ether at 0 C to give the stereochemi-cally pure anti diastereoisomer (55). The combination of these methods with asymmetric acylation provided an effective solution to the asymmetric aldol problem (Scheme 6). In contrast, the reduction of a-methyl-3-keto esters with zinc borohydride was highly syn selective when the ketone was aromatic or a,3-unsaturated, but less reliable in aliphatic cases. Hydrosilylation also provided complete dia-stereocontrol (Scheme 7). The fluoride-mediated reaction was anti selective ( 8 2) while reduction in trifluoroacetic acid favored production of the syn isomer (>98 2). No loss of optical purity was observed under these mild conditions. 

Henkel-Loctite appears to have been careful to avoid the patent minefield laid by 3M and Dow. Their patent strategy in this field has involved mainly the use of metal alkali borohydrides [113,114], or tetralkylboranes [115-117]. In particular, alkali metal trialkyl borohydrides are used, the alkali metal salt being selected from lithinm triethylborohydride, sodium triethylborohydride, potassium triethylborohydride, lithium tri-sec-butylborohydride, sodium tri-sec-butylborohydride, potassium tri-sec-butylborohydride, and lithium triethylborodeuteride. 

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