Organolithium reagents 2-amino alcohol

In some cases the yields were poor due to competing deprotonation of the substrate by the organolithium reagent. Deprotonation was the predominant reaction with methyllithium or when (Z)-2-(l-alkenyl)-4,5-dihydrooxazoles were employed. The stereochemical outcome has been rationalized as occurring from a chelated transition state. The starting chiral amino alcohol auxiliary can also be recovered without racemization for reuse. 

By the extension of the above-mentioned stereoselective asymmetric addition of alkylithiums to other organolithium reagents such as lithium salts of methyl phenyl sulfide, 2-methylthiazoline, trialkylsilylacetylene, N-nitroso-dimethylamine, and acetonitrile, chiral oxiranes (95) U1), thiiranes (96) nl), acetylenic alcohols (98) 112), and amino alcohols (97) U1) were readily obtained. 

Non-enolizable amides, for example N,N-dialkyl pivalamides [212], benzamides, thiobenzamides [213], or phosphinamides (Ph2P(0)NR2[214]), can be lithiated a to the amino group by treatment with sBuLi[54, 213, 215] or tBuLi[216], without further additives, in THF at -78 °C. N,N-Dimethylbenzamides can be attacked at the carbonyl group by these organolithium reagents to yield ketones [217] or alcohols, but with sterically more demanding amides metalation is usually faster than addition. 

Organolithium reagents (primary, secondary, tertiary, aryl and vinyl) also add in excellent yield to a-alkoxyaldehyde dimethylhydrazones (146) equation 19) with high threo diastereoselectivity (Table 9). Hydrogenolytic cleavage of the resultant hydrazines provide an attractive route to rAreo-2-amino alcohols. 

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