Addition organolithium species

The conjugate addition substrate that we were considering bore an obvious resemblance to Stork s however, it would incorporate a free NH and OH, as well as a more sensitive aldehyde. In this light, an approach involving reactive organolithium species seemed unlikely to be successful, and a few experiments quickly validated this surmise. We therefore sought a precursor that could... 

A major problem in the development of catalytic asymmetric 1,4-additions of RLi reagents is the high reactivity usually associated with organolithium species. One solution has been found in the stoichiometric formation of the corresponding chiral cuprates ee s of up to 99% have been reported [20]. An impressive example of the use of a substoichiometric quantity (33 mol%) of chiral ligand is to be found in... 

The mixed-metal Li(/x-0)Al-based complex CeHgO (THF)2 LiAl[(R)-binol]2 has been a source of great interest recently by virtue of its ability to catalyse [69, 70] the conjugate addition of organolithium species to a, -unsaturated... 

The thiophilic addition of aliphatic Grignard reagents to dithioesters deserves some comment. Although they are less reactive than organolithium compounds, their reactions are selective. With enethiolizable dithioesters, enethiolization cannot be avoided with the organolithium species, and at low temperatures this can become exclusive [332]. Enethiolization does not interfere in the case of the less... 

The addition of a full equivalent of CuCN to certain ortho-lithiated aromatics allows the introduction of allylic and propargylic side chains. Due to the nature of the organolithium species originally involved, the exact nature of the organocopper intermediate is unknown (equation 28)40. 

The high propensity of organolithium compounds to form mixed complexes with other organolithium species in solution has been utilized successfully in synthesis using chiral lithium amides. Either the chiral lithium amides have been added to organolithium reagents in an effort to achieve asymmetry in addition reactions, or various additives have been introduced to alter the reactivity or selectivity of the chiral lithium amides themselves, e.g. in deprotonation reactions. 

Addition of alkyllithium reagents to pseudoephedrine amides leads to the formation of enantiomerically enriched ketones (eqs 9 and 10). The protocol developed to transform alkylated pseudoephedrine amides into ketones was optimized to avoid premature breakdown of the tetrahedral intermediate generated following addition of the organolithium species to the amide. ... 

Sparteine 7 is also an excellent chiral ligand for the asymmetric Michael addition of chirally fixed organolithiums (Eq. (12.8)) [25]. The choice of ligand for the lithium cation provides control of 1,2- vs 1,4-addition of organolithium species to cycloalkenones. Furthermore, in these addition reactions, two contiguous stereocenters were constructed with high diastereo- and enantioselectivities. 

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