Lithium t-Butyl(diisobutyl)aluminum Hydride


[62779-60-6]  · C12H28AlLi  · Lithium t-Butyl(diisobutyl)aluminum Hydride  · (MW 206.28)

(sterically hindered and mild reducing agent for aldehydes, ketones, a,b-unsaturated ketones, esters, and lactones1-5)

Physical Data: see Diisobutylaluminum Hydride and t-Butyllithium.

Solubility: see Diisobutylaluminum Hydride and t-Butyllithium; reactions using the title reagent sol THF, toluene, hexane.

Preparative Method: prepared in situ by dropwise addition of equimolar amounts of t-butyllithium in hexane to a solution of diisobutylaluminum hydride in hexane at -78 °C followed by dilution with THF at 0 °C; a suspension is formed when toluene is used in place of THF.4

Handling, Storage, and Precautions: see Diisobutylaluminum Hydride and t-Butyllithium.

Stereoselective Reductions.

This mixed reducing reagent provides a convenient method for converting sterically hindered ketones into alcohols (eq 1).1 Exceptionally high stereoselectivity is reported, even with an unhindered bicyclic ketone such as norcamphor (eq 2).1b Reduction of conformationally rigid and hindered bicyclic ketones such as decalin derivatives has been reported to give a single stereoisomer in quantitative yield (eq 3).2

Regioselective Reductions.

This mixed reagent has been used effectively to reduce a lactone in the presence of an ester in good yield (eq 4).3 The absence of overreduction under the reaction conditions is notable.

Lithium n-Butyl(diisobutyl)aluminum Hydride, which is similar to the title reagent, reduces a,b-unsaturated ketones to allyl alcohols.4 The reduction of enones by the title reagent in the presence of Methylaluminum Bis(2,6-di-t-butyl-4-methylphenoxide) (MAD) results in reversal of the selectivity (eq 5).5

1. (a) Kovacs, G.; Galambos, G.; Juvancz, G. Z. S 1977, 171. (b) Kim, S; Ahn, K. H.; Chung, Y. W. JOC 1982, 47, 4581.
2. Trost, B. M.; Nishimura, Y.; Yamamoto, K.; McElvain, S. JACS 1979, 101, 1328.
3. Bhide, R. S.; Levison, B. S.; Sharma, R. B.; Ghosh, S.; Salomon, R. G. TL 1986, 27, 671.
4. Kim, S.; Ahn, K. H. JOC 1984, 49, 1717.
5. Nonoshita, K.; Maruoka, K.; Yamamoto, H. BCS 1988, 61, 2241.

Chang-Ho Byeon

The Ohio State University, Columbus, OH, USA

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