5/31/2023 0 Comments Cyclic ester with lda and ch3ch2iWe have begun addressing some of these questions in the context of lithium diisopropylamide (LDA), 4 - 9 a prevalent base in organic synthesis. 3 Does the marked tendency of HMPA to serially solvate organolithiums foreshadow a similar structural diversity in the rate-limiting transition structures? Do dramatic accelerations result from the capacity of HMPA to promote high solvation numbers and low aggregation numbers in the rate-limiting transition structures? Why does HMPA sometimes fail to elicit high reactivities? 2 Despite the sound understanding of how HMPA influences the structures of lithium salts, the oft-cited influence of HMPA on reactivity is not well understood and leaves many questions unanswered. 2 Their spectroscopic analyses of lithium salts in the limit of slow exchange of free and lithium-ion-coordinated HMPA offer intimate details of HMPA-mediated deaggregation and ionization. 1 A preponderance of what is known about solvation of lithium ions by HMPA derives from the studies of Reich and coworkers. Hexamethylphosphoramide (HMPA) is one of the most prominent additives used to influence the yields, rates, and selectivities of organolithium reactions.
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