Hydride Super

Super-Hydride will reduce ketones and aldehydes, of course, but it is not used extensively unless the stereochemistry of the alcohol product can be influenced by this reagent and there are no other groups in the molecule that are reduced by this reagent. In Lhommet s synthesis of (-)-porantheridine, reduction of the ketone unit in 140 gave a 4 1 mixture of 141 and 142, in 99% yield.Esters are also reduced to alcohols, even in the presence of a lactam. 74 j e nucleophilicity of Super-Hydride usually leads to 1,2-reduction of 

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L-Selectride or Super Hydride, 67°, 88-92% yield. Other methods for converting thebaine to oripavine have not been successful. ... 

Methyl-3-(tosyloxymethyl)perhydropyrido[l,2-c][l,3]oxazin-l-one 103 was detosylated by treatment with LiBEt3H (Super-Hydride ) (98T13505). 

A simple and general method for the preparation of surfactant-free, thiol-functionalized iridium nanoparticles was reported by Ulman and coworkers in 1999 [11], The synthesis consisted of a reduction of the dihydrogen hexachloroiri-date (IV) H2lrCl6 H20 precursor by lithium triethylborohydride ( super-hydride ) in the presence of octadecanethiol (C18H37SH) in tetrahydrofuran (THF) (Scheme 15.1). The obtained iridium nanoparticles were crystaUine with fee (face-centered cubic) packing, and showed a wider size distribution with diameters ranging from 2.25 to 4.25 nm. 

Replacement of hydrogen by alkyl groups gives compounds like lithium triethylborohydride (Super-Hydride ) [100], lithium tris sec-butyl)borohydride [101] (L-Selectride ) and potassium tris sec-butyl)borohydride (K-Selectride ) [702], Replacement by a cyano group yields sodium cyanoborohydride [103], a compound stable even at low pH (down to 3), and tetrabutylammonium cyanoborohydride [93],... 

N-Methylation of 3 and reduction of the crystalline oxazolidinone 4 with lithium aluminum hydride was found to give a superior yield of DAIB (5) and a more easily purified product than exhaustive methylation of 2 with methyl iodide and reduction of the quaternary methiodide with Super-Hydride. Recently, a modified version of DAIB, 3-exo-morpholinoisoborneol MIB), was prepared by Nugent that is crystalline and that is reported to give alcohols in high enantiomeric excess from the reaction of diethylzinc with aldehydes. ... 

Notes An extremely powerful source of hydride. If one assigns a relative value of 1 for the nucleophilic character of hydride from NaBH , the hydride from LiAIH4 is about 250 times more reactive and that from Super hydride is about 10,000 times more reactive. 

Lithium triethylborohydride (Super-Hydride) is a much more powerful reducing agent than lithium aluminium hydride. It is useful for the reductive dehalogenation of alkyl halides, but unlike lithium aluminium hydride does not affect aryl halides. It is available as solution in tetrahydrofuran in sealed containers under nitrogen. The solutions are flammable and moisture sensitive and should be handled with the same precautions as are taken with other organometallic reagents (see Section 4.2.47, p. 442). 

Woo recently developed a rapid, highly linear-selective dehydrocoupling catalyst system of phenylsilane CpjMCL/Hydride (C p = C5H5 or C5Me5 M = Ti, Zr, Hf Hydride = Red-Al, Selectride, Super Hydride) combination catalysts [Eq. (2)].11,17... 

Although a transition metal was not involved, the dehydrocoupling of the secondary hydrosilane, 1,1-dihydrotetraphenylsilole, to polymers with Mw values ranging from 4000 to 6000 (polydispersities ranged between 1.1 and 1.2) in the presence of catalytic quantities of Red-Al, L(N or K)-Selectride or Super-Hydride has been reported.1353 This is the only currently published example of polymeric material produced from a secondary silane. It is interesting that this secondary silane is a heterocyclic system where steric interactions (from substituents at silicon) have been reduced, although the fact that there are phenyl groups on the a-carbon, makes this a rather extraordinary result. 

Super Hydride is one of the most powerful nucleophilic reducing agents available, capable of reducing many functional groups. It is also highly selective. The exocyclic double bond in aryl-substituted fulvenes has an increased polarity, due to the inductive effects of their respective aryl groups. This increased polarity allows for selective nucleophilic attack at this double bond and not at the diene component of the fulvenes. Other examples of the nucleophilic addition of hydrides to substituted fulvenes (albeit with alkyl or unsubstituted phenyl group functionality)... 

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