Diisobutylaluminum hydride unsaturated ketones

Diisobutylaluminum benzenetellurolate, prepared from diphenyl ditellurium and diisobutylaluminum hydride, adds in a 1,4-fashion to a,/i-unsaturated aldehydes, ketones, and carboxylic acid esters to give as intermediates /i-phenyltelluro-substituted aluminum enolates that can be hydrolyzed to the carbonyl compounds or reacted with aldehydes to produce aldol adducts2. 

Cyclopropanation of a,jS-unsaturated AT-methoxy-AT-methylamides 5 with dimethyloxo-sulfonium methanide afforded the cyclopropanecarboxamides 6 in yields far superior to those obtained with the corresponding a,/J-unsaturated ketones. In almost all cases, the trans-isomer was exclusively obtained in analogy to the cyclopropanation of the corresponding unsaturated ketones. The oxygen atom of the methoxy group on the A -methoxy-A -methyl-amide 5 was found to facilitate the reaction. The substituted amides 6 can be converted to ketones (methylmagnesium bromide), aldehydes (diisobutylaluminum hydride) and carboxylic acids (potassium rerf-butoxide/water). It is noteworthy that cyclopropanecarbaldehydes and -carboxylic acids, which are not directly accessible from the corresponding a,)8-unsaturated systems under standard cyclopropanation reactions, can be obtained indirectly by this method. 

Ethynylnickel compounds, prepared from aluminum acetylides and nickel acetylace-tonate pretreated with diisobutylaluminum hydride, also undergo insertions with a, 8-unsaturated carbonyl compounds to form enolates which hydrolyze to 4-ynones . Similarly, vinylnickel derivatives from vinylzirconium compounds and nickel acetylace-tonate add to a, 8-unsaturated ketones to give enolates ... 

Peltier and Ellman reported on an asymmetric synthesis of 2,4,6-trisubstituted piperidines 258 with excellent stereoselectivity. The starting chiral sullinamide 255 was prepared by the Michael addition of ketimine and a,(3-unsaturated ketone. Treatment of 256 with L-Selectride followed by Dess-Martin periodinane (DMP) oxidation produced iy -A7-sulfinylamino ketone 257 with a high diastereomeric ratio, whereas NaBH4-Ti(OEt)4 reduction of 256 followed by DMP oxidation afforded the anti isomer of 258 with 87 13 diastereomeric ratio. 257 underwent alkylative cyclization by acidic treatment followed by diisobutylaluminum hydride (DIBt L-H) reduction to afford 2,4,6-trisubstituted piperidines 258 with excellent diastereoselectivity (Scheme 40.57). 

BF3 OEt2 followed by Diisobutylaluminum Hydride is used for the 1,2-reduction of y-amino-a,p-unsaturated esters to give unsaturated amino alcohols, which are chiral building blocks for a-amino acids. a,p-Unsaturated nitroalkenes can be reduced to hydroxylamines by Sodium Borohydride and BF3-OEt2 in THF extended reaction times result in the reduction of the hydroxylamines to alkylamines. Diphenylamine-borane is prepared from sodium borohydride, BF3-OEt2, and diphenylamine in THF at 0°C. This solid is more stable in air than BF3-THF and is almost as reactive in the reduction of aldehydes, ketones, carboxylic acids, esters, and anhydrides, as well as in the hydrob-oration of alkenes. 

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