Sodium hexamethyldisilazide crystal structure

Since most of the synthetically useful enolate anions described in the previous section are prepared by the reactions of enolizable substrates with alkali metal amide bases, it is appropriate to note a few structures of these amide bases. The common bases in synthetic organic chemistry include LDA and LHMDS. The structures of both of these bases are known as the THF solvates.Both of these compounds form bis-solvated dimers corresponding to structure (201). The diethyl ether solvate of LHMDS also forms a bis-solvated dimer (202).Sodium hexamethyldisilazide crystallizes as an unaggregated monomer from benzene solution.Two different cryst line forms of KHMDS are known as the polymeric dioxane solvate (203), ° and the unsolvated dimer (204). ... 

The tricyclic ketone (387) which has been suggested as an intermediate in the transformation of the exo-2-bromobicyclo[3,2,0]heptane-6-ones to anti-7-substituted bicyclo[2,2,l]heptan-2-ones has been isolated. Treatment of (388) with sodium hexamethyldisilazide gave (387), whose structure was confirmed by single-crystal J -ray crystallography. Reaction of (387) with potassium cyanide in methanol containing a catalytic amount of methoxide gave anti-7-cyano-5-bromobicyclo[2,2,l]-heptanone (389). The availability of (387) should allow an increase in the range of... 

---