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Keywords:

  • Lithium;
  • Sulfones;
  • Sulfoximides;
  • Sulfoxides;
  • Thioethers;
  • 1,3-Dithianes;
  • Nitriles;
  • Nitro compounds;
  • Hydrazones;
  • Coordination modes

Abstract

Acceptor-substituted lithio compounds LiA[BOND]CR1R2, in which the acceptor A is an RC(0), N[TRIPLE BOND]C, RSO2, RS(O)NR, RSO, RS, O2N, or RC(N[BOND]NR2) group, have long played an important role in organic synthesis. Their significance has grown still further in the last fifteen years, as one has increasingly learnt to employ them successfully in chemo-, regio-, diastereo-and enantioselective reactions. Remarkably, little if anything was known of the structures of these compounds. It is therefore not surprising that interest in the structures of this class of compounds has greatly increased in recent years. In the following review, we shall summarize recent research into the structures of the lithio compounds of sulfones, sulfoximides, sulfoxides, thioethers and 1,3-dithianes, nitriles, nitro compounds, and hydrazones. Crystal structure determinations from recent years are central to this study. They are supplemented by solution studies and by calculations of structures. Structural similarities and differences between the individual states of aggregation are pointed out wherever possible, as is also the relationship between structure and reactivity.