Selective manipulation of only one of two similar sites within a molecule ‘odin reactions’: Strategic advantage for synthesis and tactics available

Abstract

Approaches used to effect selective reaction at one of two or more similar sites in a molecule are reviewed. The nature of the problem is defined and the strategic advantage to be gained through the use of symmetrical intermediates is outlined early and re‐emphasised throughout the discussion with specific examples of multistage syntheses of important products. The various tactics used to effect site selectivity in a late synthetic step are described in a logical sequence and presented in a form aimed to help in the design of syntheses of unsymmetric products from symmetric intermediates.

Complexity of synthetic routes: Linear, convergent and reflexive syntheses1Electronic supplementary information (ESI) available: values of indices used to calculate analytical functions for routes 1–3. See http://www.rsc.org/suppdata/nj/b2/b210844p/

“…When symmetry is present, the synthetic complexity may be decreased by it, provided that synthetic methodology is available to take advantage of it. 17 Such synthetic methods have been called ' Odin reactions, ' 18 and the development of additional ones would help approaches based on symmetry to reach their full potential. An example of the effect of symmetry on synthetic complexity is the reflexive synthesis of a molecule from two or more identical components (vide infra).…”