For reducing carbonyl

The hydride donor with a covalent M—H bond that is very frequently used for reducing carbonyl groups is iBu2AlH (DIBAL stands for diisobutylaluminum hydride). It can be used in ether, THF, toluene, saturated hydrocarbons, or CH2C12. 

Functional group transformations classical and chemoselective methods for oxidation and reduction of organic substrates, and the availability and utilization of regio-, chemo-, and stereoselective agents for reducing carbonyl compounds... 

Several theoretical studies have considered LiH addition as a model for the more computationally difficult L1A1H4 and NaBH4 [45]. However, reaction of aldehydes and ketones with LiH seldom if ever leads to reduction [46]. AIH3, while less commonly used than the complex boron and aluminium hydrides, is useful for reducing carbonyls [47] and therefore is a suitable model for computational study. Calculations [2, 5] show that gas-phase reduction of formaldehyde by AIH3 occurs by formation of complex 1, which rearranges via a four-centre transition state to form an aluminium methoxide product. Two conformational isomers of... 

We have reported recently a new entry of such species which appeared very useful for reducing carbonyl compounds and interesting for elucidating the mechanism. Bis(l,2-... 

Catalytic hydrogenation would not be suitable for this transformation because H2 adds to carbon-carbon double bonds faster than it reduces carbonyl groups... 

Clemmensen reduction (Section 12 8) Method for reducing the carbonyl group of aldehydes and ketones to a methylene... 

Interestingly, true hydrides, such as NaH and KH, do not reduce carbonyl groups. Using energies of hydride and methoxide (at left), calculate AH xn for the reduction of formaldehyde by H. Is this reaction more or less favorable than those based on ZH4 Can the low reactivity of NaH and KH be attributed to thermodynamic factors, or must kinetic factors be responsible ... 

A variety of catalysts including copper, nickel, cobalt, and the platinum metals group have been used successfully in carbonyl reduction. Palladium, an excellent catalyst for hydrogenation of aromatic carbonyls is relatively ineffective for aliphatic carbonyls this latter group has a low strength of adsorption on palladium relative to other metals (72,91). Nonetheless, palladium can be used very well with aliphatic carbonyls with sufficient patience, as illustrated by the difficult-to-reduce vinylogous amide I to 2 (9). 

Anhydrides are reduced with relative ease. McAlees and McCrindle 20) established the following increasing order of difficulty for various carbonyls acid chlorides > aldehydes, ketones > anhydrides > esters > carboxylic acids > amides. Reduction may proceed by 1,2-addilion of hydrogen or by cleavage of an oxygen-carbonyl bond. If 1,2-addition to the carbonyl occurs, as in the presence of strong protic acids over palladium, 1,1-diesters are formed by acylation 26). 

Silanes And Base. In the presence of bases, certain silanes can selectively reduce carbonyls. Epoxy-ketones are reduced to epoxy-alcohols, for example with (MeO)3SiH and LiOMe. ° Controlling temperature and solvent leads to different ratios of syn- and anti- products.Silanes reduce ketones in the presence of BF3-OEt2 ° and transition metal compounds catalyze this reduction. ... 

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