Dibenzylamino ketones

L-Selectride reduction of a-dibenzylamino ketones. Interestingly, a-benzyloxy ketones give anri-l,2-diol monobenzyl ethers with low isomer ratios (e.g, anti syn =6 1) which can be increased dramatically by changing the reducing agent to lithium tri-n-butylborohydride (>99 1). ... 

Quantitative yields are realized when a-(/V,/V-dibenzylamino) ethyl ketones undergo aldol reactions with aldehydes. The reaction proceeds in a highly diastereoselective manner... 

Several a./f-unsaturated-y-dibenzylamino esters 1 and ketones 3 were epoxidized with tm-butyl hydroperoxide in the presence of potassium tm-butoxide in tetrahydrofuran and liquid ammonia to give xy/t-epoxides 2 and 4. respectively, in good yield and with better than 98 2 synjanti ratio25. 

S)-2-(N,iV-Dibenzylamino)alkyl carbamates 83, prepared by a few synthetic steps from L-amino acids, are easily deprotonated by means of sec-butyllithi-um/TMEDA [Eq. (26)] [63,67,68]. A selection between the diastereotopic protons pro-R-H and pro-S-B. takes place to give the lithium carbanions 85 and 87 which are formed in unequal amounts, and these are trapped with strict stereoretention by several electrophiles (MeOD, CO2, ClC02Et, Me3SiCl, RjSnCl, Mel, aldehydes, ketones and acid chlorides). The substrate-induced stereoselection is... 

Remarkably high stereoselectivity is obtained by means of the sodium enolate of a-N,N-dibenzylamino-substituted ketone 51, a counter-ion not very frequently used in stereoselective aldol additions. In this instance, however, the sodium enolate turned out to be more efficient than the lithium analog. The predominant formation of the main diastereomeric product 52a rather than 52b is explained by an open transition state, assumed to be strongly favored over the cyclic transition state, when the more ionic sodium enolate is used rather than the corresponding lithium reagent (Eq. (24)) [103]. 

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