Diisobutylaluminum hydride structure

Digitoxigenin, structure of, 1097 Digitoxin, structure of, 989 Dihalide, alkynes from, 261 Dihedral angle, 94 Diiodomelhane. Simmons-Smith reaction with, 228-229 Diisobutylaluminum hydride, reaction with esters, 812 structure of, 699 Diisopropylamine, pK.d of, 923 1,3-Diketone, pfCa of, 852 Dimethyl disulfide, bond angles in, 20 structure of, 20 Dimethyl ether, electrostatic... 

The isomerization of an allylic amine to an enamine by means of a formal 1,3-hydrogen shift constitutes a relatively small structural change. However, this transformation could be extremely valuable if it could be rendered stereoselective. In important early studies, Otsuka and Tani showed that a chiral cobalt catalyst, prepared in situ from a Co(ii) salt, a chiral phosphine, and diisobutylaluminum hydride (Dibal-H), can bring about the conversion of certain pro-chiral olefins to chiral, isomeric olefins by double bond migra-... 

Selective reduction to aldehydes can also be achieved using /V-methoxy-iV-methyla-mides.49 Lithium aluminum hydride and diisobutylaluminum hydride have both been used as the hydride donor. The partial reduction is believed to be the result of the stability of the initial reduction product. The /V-mcthoxy substituent permits a chelated structure which is... 

A structurally unusual 3-blocker that uses a second molecule of itself as the substituent on nitrogen is included here in spite of the ubiquity of this class of compounds. Exhaustive hydrogenation of the chromone (13-1) leads to a reduction of both the double bond and the carbonyl group, as in the case of (11-2). The car-boxyhc acid is then reduced to an aldehyde (13-2) by means of diisobutylaluminum hydride. Reaction of that intermediate with the ylide from trimethylsulfonium iodide gives the oxirane (13-3) via the addition-displacement process discussed earlier (see Chapters 3 and 8). Treatment of an excess of that epoxide with benzylamine leads to the addition of two equivalents of that compound with each basic nitrogen (13-4). The product is then debenzylated by catalytic reduction over palladium to afford nebivolol (13-5) [16]. The presence of four chiral centers in the product predicts the existence of 16 chiral pairs. 

C-NMR spectra were in accord with the formation of only one silicon-containing species having only one type of isopropyl group. According to the authors, the isomeric sulfonium ion structure and the dimer structure can be eliminated with a high degree of confidence. (4) Treatment of the product with diisobutylaluminum hydride led only to the recovered silane precursor. 

A significant modification of the Bradsher method was introduced recently by Castle to effect homoannulation of structurally appropriate methyl derivatives of condensed thiophenes in four steps (Scheme 28a, where NBS = N-bromosuccinimide DIBAL = diisobutylaluminum hydride).658 106a l26a The main feature is the conversion of a methyl substituent to the—CH=CH— unit of a peri-condensed ring structure. Yields reported for the steps in the transformation 358c -> 76 are 76, 72%, and 32% (last two steps). The intermediate aldehyde 358d undergoes cyclization at C-l. In the same manner, overall yields of 6% for 34a, 9% for 77, and 27% for 79 were obtained. 

The objective of this chapter is to examine the basic research on diene (butadiene, isoprene, and piperylene) polymerisation with the LnHalj-nL-AlRj (Ln = lanthanide, Hal = halogen, ligand (L) = tributyl phosphate (TBP), AlRj = triisobutylaluminum and diisobutylaluminum hydride) catalytic system. The chapter will analyse the role of such factors as the electronic and geometric structure of bimetallic active centres, anti-syn and 7t-o-transitions of the terminal units of the growing polymer chains and the nature of the lanthanide, diene, and organoaluminum component in the mechanism of stereoregulation. 

Reduction of an esfer to a primary alcohol can be viewed as two successive hydride ion transfers, as shown in the mechanism we just presented. Chemists wondered if it might be possible to modify the structure of the reducing agent to reduce an ester to an aldehyde and no further. A useful modified hydride-reducing agent developed for this purpose is diisobutylaluminum hydride (DIBALH). 

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