Non-chelation-controlled Grignard-like and aldol additions to 0-silyl protected a-hydroxyketones are possible for the first time using titanium reagents of reduced Lewis-acidity.

30 years after their postulation, the existence of Cram chelates has now been demonstrated 13C‐NMR spectroscopically with the examples 2a/2b. They are formed from 1 and CH3TiCl3. As shown by labeling experiments and kinetic measurements the methyl transfer 2 → 3 proceeds intermolecularly (not intramolecularly).

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blicklicher Bildung eines schwarzen fliissigen Clathrats. Aus diesem scheiden sich farblose, luftempfindliche Kristalle von [AlMe2~[15]Krone-SNAlMe2CI21 ab. V=2462 A3, Z=4. CAD-4-Diffraktometer, MoK,, 2.OS28S46". 1326 gemessene Reflexe mit /23a(/). MULTAN-und Differenz-Fourier-Methoden, Wasserstoffatome wurden gefunden und verfeinert, alle Nicht-Wasserstoffatome wurden anisotrop verfeinert, R = 0.044. Angew Chem 99 (1987) Nr 5 419 Q VCH Verlagsgesellschajr mbH. 0-6940 Wemherm, 1987 0044-8249/87/0505-0479 0 02 50/0