Lithium tri-sec butylborohydride

Although sodium borohydride appears to be the most popular reducing agent, a significantly better endo selectivity was achieved in the reduction of bicyclo[3.2.0]hept-2-en-6-ones using lithium tri-fer -butoxyaluminum hydride instead, e.g. formation of 3.251 In another study,99 lithium tri-sec-butylborohydride was found to reduce (la,4a,5a)-4-benzy)oxycarbonyl-2-oxabi-cyclo[3.2.0]heptan-6-one to (la,4oc,5a,6/i)-4-benzyloxycarbonyl-2-oxabicyclo[3.2.0]heptan-6-ol (4) with complete stereoselectivity. 

Optically pure 1,2-diols.1 The acyllactones 1, obtained by reaction of a Grig-nard reagent with the acid chloride derived from (R)-( -)- or S-( + )-glutamic acid, are reduced by lithium tri-sec-butylborohydride almost exclusively to syn-alcohols (2), regardless of the nature of the R group. In contrast, reduction of 1 with sodium... 

Stereoselective acyclic enolization2 This reaction can sometimes be achieved by conjugate reduction of acyclic a,(3-enones by lithium tri-sec-butylborohydride (1). When an enone reacts with 1 mainly by 1,2-reduction Li/NH3 can be used for conjugate reduction. In at least one case reduction with 1 is more stereoselective than that with Li/NH3. The stereoselectivity in general can be correlated with conformational preferences of enones.3... 

Enol triflatesfrom affi-enones.1 The reaction can be carried out by conjugate reduction of the enone with lithium tri-sec-butylborohydride followed by reaction of the resulting enolate with N-phenyltriflimide. The method is generally useful, but 1,2-reduction can predominate in the case of (3,(3- or even y,y-disubstituted a,(3-enones. 

Oxidation reactions r-Butyl hydroperoxide-Dialkyl tar-trate-Titanium(IV) isopropoxide, 51 m-Chloroperbenzoic acid, 76 Reduction reactions Chlorodiisopinocampheylborane, 72 Diisobutylaluminum hydride-Tin(II) chloride- (S) -1 - [ l-Methyl-2-pyrrolidi-nyljmethylpiperidine, 116 Lithium borohydride, 92 Lithium tri-sec-butylborohydride, 21 B-3-Pinanyl-9-borabicyclo[3.3.1]-nonane, 249... 

SlLYL ENOL ETHERS Chiorotrimethylsilane-Zinc, 82 Lithium amides, chiral, 159 Lithium tri-sec-butylborohydride, 167 Organotin reagents, 211 Osmium tetroxide-Trimethylamine N-ox-ide-Pyridine, 223... 

Lithium dialkylcuprates-Boron trifluoride etherate, 208 Lithium dibutylcuprate-Boron trifluoride etherate, 208 Lithium dimethylcuprate-Boron trifluoride etherate, 208 Lithium tri-sec-butylborohydride, 21, 167, 248... 

The formed ketone is selectively reduced to an alcohol with lithium-tris-sec-butylborohydride (L-Selectride ) at -78 °C in only 30 min.. Only one diastereomer is built. Because lithium belongs to the non-chelating cations, the reaction proceeds through transition state 48 proposed by Felkin and Anh. 1 To remind In the most stable conformation the largest group of the stereogenic center is perpendicular to the carbonyl group. 

The NMR spectrum of the cis-fused quinolizidol (64a) and its derivatives showed the presence of an equilibrium mixture of conformers where the form with an axial OH and equatorial phenyl group was only a minor component. The signal of H-l in 64b-d appears at <5 4.0-4.1 ppm as a triplet with a coupling constant of 4-5 Hz and W1/4 of 13-14 Hz. H-3 was in part unresolved from H-l in 64a,e and in 64c,d was a broad multiplet (a triplet of triplets with J 8-9 and 4.5 Hz) with W1/4 equal to 25-28 Hz. These couplings of H-l and H-3 favor that conformation with an axial phenyl and an equatorial hydroxyl. Compound 64a was synthesized by reduction of cis-fused quinolizidone (65b) with NaBH4 to yield mixture of 64a and its epimer in 1.3 1 ratio or with lithium tri-sec-butylborohydride, where 65% conversion to axial alcohol was observed. 

C2HLi 1111-64-4) see Levonorgestrel lithium ethyl acetate (C4H7Li02 189811-59-4) see lloprost lithium tri-sec-butylborohydride (C 2H28BLi 38721-52-7) see Rosiglitazonc loratadine... 

Reduction of a, -unsaturated nitroalkenes.1 These nitroalkenes are reduced by lithium tri-sec-butylborohydride or by lithium triethylborohydride to lithium nitronates, which are hydrolyzed by dilute acid or by silica gel to nitroalkanes (equation I). 

Stereoselective reduction of ketones.1 This borohydride (1) is comparable to lithium tri-sec-butylborohydride (4, 312-313) for stereoselective reduction of cyclic ketones to the less stable alcohols, but less stereoselective than lithium trisiamylborohydride (7, 2lb-217). The by-product formed in reductions with 1 can be removed as an insoluble ate complex formed by addition of water, simplifying isolation of the reduction product. 

Lithium tri-sec-butylborohydride, also known as L-selectride, is a metal hydride reagent that contains three sec-butyl groups bonded to boron. When this reagent is used to reduce cyclic ketones, one stereoisomer often predominates as product. Explain why the reduction of 4-ferf-butylcyclohexanone with L-selectride forms the cis alcohol as the major product. 

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