Reduction diisobutylaluminum hydride

Mono MOM derivatives of diols can be prepared from the ortho esters by diisobutylaluminum hydride reduction (46-98% yield). In general, the most hindered alcohol is protected. ... 

Perlmutter used an oxymercuration/demercuration of a y-hydroxy alkene as the key transformation in an enantioselective synthesis of the C(8 ) epimeric smaller fragment of lb (and many more pamamycin homologs cf. Fig. 1) [36]. Preparation of substrate 164 for the crucial cyclization event commenced with silylation and reduction of hydroxy ester 158 (85-89% ee) [37] to give aldehyde 159, which was converted to alkenal 162 by (Z)-selective olefination with ylide 160 (dr=89 l 1) and another diisobutylaluminum hydride reduction (Scheme 22). An Oppolzer aldol reaction with boron enolate 163 then provided 164 as the major product. Upon successive treatment of 164 with mercury(II) acetate and sodium chloride, organomercurial compound 165 and a second minor diastereomer (dr=6 l) were formed, which could be easily separated. Reductive demercuration, hydrolytic cleavage of the chiral auxiliary, methyl ester formation, and desilylation eventually led to 166, the C(8 ) epimer of the... 

Examples of both hydroboration55 and diisobutylaluminum hydride reduction of x-enam-inocyclobutanone to the alkyl-substituted cyclobutanonc56 have also appeared. Only scarce experimental details appear in the literature for these reactions. 

A convenient synthesis of a-acylamino aldehydes (541) has, for example, been developed which is based on the transformation of the a-acylamino acid (540) into its acylimidazolide with carbonyldiimidazole (79CC79). Diisobutylaluminum hydride reduction of the imi-dazolide then affords the aldehyde, generally in high optical purity (equation 6). 

The mechanism of diisobutylaluminum hydride reduction involves formation of a six-membered transition state with aluminum complexed to the carbonyl of the ester group, which is required for the delivery of the hydride from the electrophilic aluminum hydride to the carbonyl group. The alkoxy moiety is then displaced during workup resulting in the desired peptide aldehyde. This mechanism accounts for the fact that the reduction stops after the conversion of the ester into the aldehyde. 23 ... 

Amino acid and peptide aldehydes with one to three residues have been prepared successfully using diisobutylaluminum hydride. Z-Protected amino aldehydes such as Z-Leu-H, Z-Phe-H, Z-Cys(Bzl)-H, Z-Pro-H have been synthesized with little or no racemization (Table l). 5 The diisobutylaluminum hydride reduction can be used with both peptide esters and Z amino acid esters. However, the Boc protecting group is less stable when refluxed with diisobutylaluminum hydride, thus resulting in its loss while reducing Boc-Ala-OMe or Boc-Ser(OBzl)-OMe. 13 ... 

Sicker, D. and Hartenstein, H. 1993. A new general approach to the 2-hydroxy-2H-1,4-benzoxazin-3(4H)-one skeleton via diisobutylaluminum hydride reduction of 2,3-dioxo-1,4-benzoxazines. Synthesis, 771-772... 

In the early investigations discussed in Chapter 3 of Volume XIII (3), the ipecac alkaloid protoemetine (11) was synthesized (23,24) both in its racemic and natural (—) form by diisobutylaluminum hydride reduction of the... 

The BPS group is more stable toward acidic hydrolysis than TBS or the TIPS groups. It survives DIBAL (diisobutylaluminum hydride) reductions, cleavage of THP with aqueous AcOH, and cleavage of isopropylidene and benzylidene acetals with aqueous CF3CO2H. BPS-Cl has been used to selectively protect primary OH groups in inositol (hexahydroxycyclohexane). ... 

Particularly satisfying was the ease with which 157 was homologated to 158 (92%). Reduction of the ketone carbonyl in a chemoselective manner was not possible because of the steric protection it benefits from. This potential complication was skirted when it was found that the hydroxy lactol produced by diisobutylaluminum hydride reduction responded to the Fetizon reagent only at the five-membered site to deliver 159. With the stereochemistry of 159 securely established by NOE analysis, no obstacles were encountered during acetylation and the subsequent completion of sidechain construction. 

Domino reduction/aldol cydization was applied for the synthesis of ( )-fredericamydn A 44, a potent antitumor and antibiotic agent, by Kelly et al. [18] in 1988 (Scheme 9.10). DIBAL-H (diisobutylaluminum hydride) reduction of lactone 45 afforded an intermediate 46 having both enolate and aldehyde. Subsequent cychzation via aldol reaction gave a diastereomeric mixture of spiro hydroxy ketone 47, which was further converted into ( )-fredericamycin A 44 by sequential organic transformations. A similar strategy was employed by Mehta et al. [19] for the synthesis of bicyclo[3.3.1]nonan-9-one core of hyperforin, an antidepressant. 

In a subsequent and more complete study, Nalliah, MacLean, Rodrigo, and Manske have shown that diisobutylaluminum hydride reduction of the dehydrophthalideisoquinoline 20 gives corydaine and sibiricine. A novel and significant finding was that sibiricine can be isomerized into corydaine by simple... 

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