Peter Beak

Asymmetric syntheses of 4,5,6- and 3,4,5,6-substituted azepanes have been achieved by highly diastereoselective and enantioselective (−)-sparteine-mediated asymmetric lithiation−conjugate additions of N-Boc-N-(p-methoxyphenyl)-2,3-substituted allylamines to a β-aryl α,β-unsaturated ester followed by hydrolysis, cyclization, and reduction. Access to the enantiomeric adduct is provided by an invertive lithiation−stannylation−lithiation sequence.

The concept of the complex‐induced proximity effect (CIPE) in deprotonations is helpful in elucidating the mechanisms involved in carbanion chemistry and in planning organic syntheses. In this Review, the consequences of complexation of organolithium bases to functional groups of the substrates before the proton‐transfer step are discussed. Experimental data from kinetic measurements and isotope‐labeling experiments as well as the results of calculations in many cases point to a prelithiation complex as a reaction intermediate. Some examples from natural products synthesis illustrate how this concept can be used to obtain intermediates in a regio‐ or stereoselective manner. Of particular interest is the functionalization of positions that are remote from the coordination group.