With lithium triethylborohydrid

Unsubstituted imides, with a single stereogcnic center appended to nitrogen, are stereoselective-ly reduced with lithium triethylborohydride at — 78 C with diastereoselectivities up to 100% in the case of severe steric crowding (Ar = 2,6-dichlorophenyl) (see Appendix)46. 

Complex hydrides have been used rather frequently for the conjugate reduction of activated dienes92-95. Just and coworkers92 found that the reduction of a,ft-unsaturated ketene 5,5-acetals with lithium triethylborohydride provided mixtures of 1,4- and 1,6-reduction products which were transformed into enals by treatment with mercuric salts (equation 27). Likewise, tetrahydro-3//-naphthalen-2-ones can be reduced with L-Selectride to the 1,6-reduction products93 -95 this reaction has been utilized in the stereoselective synthesis of several terpenes, e.g. of (/ )-(—)-ligularenolide (equation 28)95. Other methods for the conjugate reduction of acceptor-substituted dienes involve the use of methylcopper/diisobutylaluminum hydride96 and of the Hantzsch ester... 

Stereoselective reaction with ketones. The reaction of ketone 1 with methyl-lithium, trimethylaluminum, and lithium letramethylaluminate shows no stcrco-specificity. The reaction with mcthylmagncsium bromide gives the two possible adducts in the ratio 2.4 1. The best stereospccificity is observed with dimethylsulf-oxonium methylide, which converts 1 into 2 and 3 in a ratio about 5 1. Reduction of the epoxides with lithium triethylborohydride gives the desired tertiary alcohols. This reaction was used in a synthesis of ( ) stemodin (4).2... 

Although molecular rearrangements of carbohydrate inflates are rare, they are not unknown [2,21,31]. Many of these rearrangements are ring-contraction reactions associated with treatment of Inflates with lithium triethylborohydride [see Eq. (10) 20,21]. Reported rearrangement reactions occurring when halide or azide ions are the nucleophiles are quite rare and are restricted to epimerization at centers next to a carbonyl group. Such reactions have been reported only for the more basic fluoride [32] and azide ions (Scheme 5) [33],... 

Species of type 3.59, in which a phosphine donor unit is linked to a skeletal phosphorus atom by a P-P bond are the least stable species, and the most difficult to prepare.106 Specifically, they are synthesized by the reaction of P-Cl bonds in the polymer with lithium triethylborohydride, LiBEt3H, which generates a P site in place of the P-Cl bond. Treatment of the polymer with Ph2PCl then yields side groups of the type shown in 3.59. Reaction with Ru3(CO)12 results in the linkage of Ru3(CO)n units (M) to the side groups. 

Upon treatment with lithium triethylborohydride in tetrahydrofuran, 2-benzoyl-l-ethenyl tellurium trichlorides produced did not produce the expected ditellurium compounds but bis[2-benzoylethenyl] telluriums2. 

To complete the synthesis of the nucleotide hosts, the hindered tweezer esters needed to be converted to the corresponding carboxylic acids. One possible method presented itself with the surprising finding that treatment of 45 with lithium triethylborohydride produced the corresponding carboxylic acid However, lithium triethylborohydride did not react at all with the more hindered ester in 27. Neither could the esters in molecular tweezers 27-30 and 48 be converted to the corresponding carboxylic acids (31-34, 49) hydrolytically. Therefore, the nucleophilic reagents, boron trichloride in methylene chloride or cyanide in hot DMSO, were employed with success [56]. 

The aminocyclitol d-48 was synthesized from l-218 (Scheme 28).103 Since direct peroxyacid oxidation of the exo-methylene group of compound l-218 had been shown to give selectively the undesired /<-spiro epoxide,35 102 it was first converted into l-219, followed by oxidation with m-CPBA to give the desired x-spiro epoxide d-220 (80%). The alcohol d-221 obtained in 73% yield by reductive cleavage of epoxide d-220 with lithium triethylborohydride (LiBHEt3) in THF was formed as a 2 3 mixture of two alcohols. However, hydrolysis of d-221 with hydrochloric acid gave d-48 (94%), which was further characterized by conversion into the pentaacetyl derivative 222 (82%). 

Reductive cleavage of cyclic ethers This complex is effective for reductive cleavage of cyclic ethers. The order of reactivity is epoxide > oxetane > tetrahydrofurane>tetrahydropyrane>oxepane. It is less effective for cleavage of acyclic ethers, except for methyl ethers. The reaction involves formation of a complex of the ethereal oxygen with aluminum r-butoxide followed by Sn2 displacement with lithium triethylborohydride. Steric and electronic Victors are involved, but yields are >90% in favorable cases. 

The perhydro-isoxazolo[2,3-fl]pyridine system offers a route to 2,6-disubstituted piperidines. For example, the reaction between styrene and the substituted 3,4,5,6-tetrahydropyridine-l-oxide (69) gives the isoxa-zolidine (70) which, on benzylation, gives 71. This was subjected to reductive cleavage of the N—O bond with lithium aluminum hydride, followed by mesylation of the aminodiol produced. Treatment of the mesylate with lithium triethylborohydride gave the trans-2,6-disubstituted piperidine... 

Unsaturated Amides. Cycloaddition of (S)-3-acryloyl-4-benzyl-2,2,5,5-tetramethyloxazolidine with Benzonitrile Oxide proceeds smoothly at 0°C to provide the corresponding oxazolidine in a 93 7 diastereomer ratio (eq 1), which is quantitatively reduced with Lithium Triethylborohydride to give the isoxazoline-5-methanol derivative without loss of enantiomeric purity. A single diastereomer of isox-azoline can be obtained when 3-acryloyl-2,2-dimethyl-4-diphenylmethyloxazolidine is employed. ... 

Table 4 Reduction of Alkyl Halides with Lithium Triethylborohydride in THF ...

The reduction with lithium triethylborohydride is far faster than that with sodium thiophenoxide, lithium aluminum hydride, or lithium borohydride. 

The sex pheromone structure, 10-methyl-2-tridecanone, was synthesized using the carboxyl group as the source of the methyl branch (lA) (Figure 6). Undecylenic acid was a-propylated and resolved via amides. The procedure followed allowed us to obtain the alcohols,(R)- and (S)-2-propyl-10-undecenol (>99.6% ee). The corresponding bromide was reduced with lithium triethylborohydride (15) then the double bond was converted to a methyl ketone by a) oxymercuration, b) reduction of the C-Hg bond with sodium borohy-dride, and c) oxidation with dichromate. The male southern corn rootworm responds only to the (R)-configuration no biological activity was noted for the (S)-enantiomer. Therefore, in this instance the racemic compound would be predicted to monitor this species adequately. 

If the reaction takes place via an anion or in a S 2 fashion, high yields of the product alkyl-cyclopropanes have been obtained. Thus, reaction of methyl 4,6-( -benzyIidene-2,3-dideoxy-2,3-C-[(7 )-(chloromethyl)ethylidene]-a-D-mannopyranoside (1) with lithium aluminum hydride in refluxing tetrahydrofuran gave methyl 4,6-0-benzylidene-2,3-dideoxy-2,3-C-isopropylidene-a-D-mannopyranoside (2) in 89% yield. Similarly, treatment of chloromethylcyclopropane 3 with lithium triethylborohydride, followed by oxidation with pyridinium chlorochromate,. gave ishwarone (4) in 75% yield. ... 

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